Synthesis and Reactivity of [PdCl2{C,N

Article
pubs.acs.org/Organometallics
Synthesis and Reactivity of [PdCl 2 {C,N-C 6 H 4 C(NHXy)NH 2 -2}] and
Neutral Palladium 1,2-Dihydroquinazolinium-4-yl Complexes:
Depalladation Reactions †
Antonio-Jesuś Martıńez-Martínez, JoséVicente,* and Marıá-Teresa Chicote
Grupo de Química Organometaĺica, Departamento de Química Inorgańica, Universidad de Murcia, Apartado 4021, 30071 Murcia,
Spain
Delia Bautista
SAI, Universidad de Murcia, Apartado 4021, 30071 Murcia, Spain
*S Supporting Information
ABSTRACT: The complex [Pd{C,N,O-C(NXy)C 6 H 4 {NC(Me)-
CHC(Me)O}-2}PPh 3 ](A) reacts with aqueous HCl and H 2 O 2 or
with aqueous HCl (HCl:Pd = 2, 3) to produce the complexes
[PdCl 2 {C,N-C(NHXy)C 6 H 4 NH 2 -2}] (1), cis-[PdCl 2 {C(
NHXy)C 6 H 4 NH 2 -2}}(PPh 3 )] (2c), and [PdCl 2 {C(NHXy)-
C 6 H 4 NH 3 -2}PPh 3 ]Cl (3), respectively. The reactions of complex 1
with L (neutral C- or P-donor ligands) give [PdCl 2 {C(NHXy)-
C 6 H 4 NH 2 }-2}L] (2). Dehydrochlorination of 2a (L = CN t Bu) occurred upon heating to give [PdCl{C,N-C(NXy)C 6 H 4 NH 2 -
2}L] (4). The complexes [PdCl{C,N-C(NXy)C 6 H 4 NH 2 -2}PPh 3 ]X (X = ClO 4 (5), TfO (5′)) were obtained by reacting 2c
with AgClO 4 or TlTfO (TfO = CF 3 SO 3 ), respectively. When 1 was reacted with NEt 3 , a dehydrochlorination/dimerization
process occurred, giving [Pd 2 Cl 2 {μ-N,C,N′-C(NXy)C 6 H 4 NH 2 -2} 2 ](6a), which, in turn, reacted in two steps with TlTfO and
NaOAc to give [Pd 2 (OAc) 2 {μ-N,C,N’-C(NXy)C 6 H 4 NH 2 -2} 2 ](6b). The reaction of 1 with 1 equiv of a neutral ligand L and a
carbonyl compound (acetone, RCHO, or R′(CHO) 3 ) affords the neutral 1,2-dihydroquinazolinium-4-yl complexes cis-
[PdCl 2 {C(NXy)CMe 2 NHC 6 H 4 -2}L] (7), cis-[PdCl 2 {C(NXy)CH(R)NHC 6 H 4 -2}PPh 3 ](8), and [{cis-PdCl 2 {C(NXy)-
CHNHC 6 H 4 -2}CNXy} 3 {μ 3 -C 6 H 3 (C 6 H 4 -4) 3 -1,3,5}] (9)), respectively. Depalladation of compounds 7 occurred when they were
heated with TlTfO, to give 2-Me-4-xylyliminium-1,4-dihydroquinoline triflate (10a). The complexes trans-[PdI{C(
NXy)CMe 2 NHC 6 H 4 -2}(CNXy) 2 ]TfO and trans-[PdI{C(NXy)C 6 H 4 NH 2 -2}(CNXy) 2 ] react in two steps with AgTfO and
PhCCH/NEt 3 to give the depalladated species 2,2-dimethyl-3-xylyl-4-phenylethynyl-1,2-dihydroquinazolinium triflate (11)
and H 2 NC 6 H 4 {C(NXy)CCPh}-2 (12), respectively. Complex 11 reacts with K t BuO or Tl(acac) to give the dinuclear
complex [Pd 2 {μ-C,N-C(NXy)C 6 H 4 NH-2}{C,N-C(NXy)C 6 H 4 NH 2 -2}(CNXy) 3 ](13).
■ INTRODUCTION
In spite of the tendency of Pd(IV) complexes to decompose
through reductive elimination to give Pd(II) complexes,
interest in their synthesis has been steadily growing because
of their involvement in catalytic organic reactions. 1 We have
recently shown that the first highly stable Pd(IV) pincer
complexes can be prepared by oxidizing the corresponding
Pd(II) complexes. 2−4 This prompted us to study the reactivity
of our pincer complex [Pd{C,N,O-C(NXy)C 6 H 4 {NC(Me)-
CHC(Me)O}-2}PPh 3 ] 5 (A; Scheme 1) with various oxidizing
agents. However, a rare hydrolysis/phosphine-abstraction
process occurred instead, producing the neutral amino-
(iminiumbenzoyl)palladium(II) complex 1 (Scheme 1). We
have recently reported that similar but cationic complexes react
with aldehydes and ketones to afford cationic 1,2-dihydroquinazolinium-4-yl
(DHQ) Pd(II) complexes. 6−8 Therefore, 1
offered the opportunity to study its reactivity toward a variety
of mono- or polycarbonyl compounds that could afford the first
family of neutral DHQ Pd(II) complexes not accessible from
their cationic homologues. A couple of neutral DHQ
derivatives obtained through a different method without
general applicability 5 have been recently reported by us.
Compounds based on the quinazoline structure are interesting
because of the pharmacological properties they display. 9
Within the experiments addressed to clarify the reactivity of 1
and its derivatives, we carried out some depalladation reactions
which, probably helped by transphobic effects, 10,11 led to the
synthesis, among others, of 4-iminium-1,4-dihydroquinoline
and 4-alkynyl-1,2-dihydroquinazolinium salts. Previous studies
on depalladation reactions leading to organic compounds,
effected by the insertion of unsaturated molecules, with or
Special Issue: F. Gordon A. Stone Commemorative Issue
Received: October 14, 2011
Published: November 29, 2011
© 2011 American Chemical Society 2697 dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
Scheme 1
without using Ag or Tl salts and/or heating, have been
previously
■
reported by Pfeffer 12 and by us. 13
EXPERIMENTAL SECTION
General Considerations. When not stated, the reactions were
carried out without precautions to exclude light or atmospheric oxygen
or moisture. Melting points were determined on a Reichert apparatus
and are uncorrected. Elemental analyses were carried out with a Carlo
Erba 1106 microanalyzer. IR spectra were recorded on a Perkin-Elmer
Spectrum 100 spectrometer with Nujol mulls between polyethylene
sheets. NMR spectra were recorded on Bruker Avance 200, 300, and
400 NMR spectrometers. The NMR assignments were performed, in
some cases, with the help of APT, COSY, HMQC, and HMBC
experiments. High-resolution ESI mass spectra were recorded on an
Agilent 6220 Accurate Mass TOF LC/MS spectrometer. The atom
numbering used in NMR assignments is shown in Chart 1. 2-
Chart 1. Numbering Scheme Used in the NMR Assignment
Iodoaniline, PPh 3 , and TfOH were purchased from Fluka. Aqueous
solutions of HCl (37%) and H 2 O 2 were purchased form Panreac and
Sigma-Aldrich, respectively. 1,3,5-Tris(4-formylphenyl)benzene was
prepared as reported in the literature. 14 The syntheses of [Pd{C,N,O-
C(NXy)C 6 H 4 {NC(Me)CHC(Me)O}-2}PPh 3 ], 5 trans-[PdI{C(
NXy)C 6 H 4 NH 2 -2}(CNXy) 2 ], [PdI{C(NHXy)C 6 H 4 NH 2 -2}-
(CNXy) 2 ]TfO, SP-4-4-[PdI{C,N-C(NHXy)C 6 H 4 NH 2 -2}CNXy]-
TfO, and trans-[PdI{C(NXy)CMe(CH 2 R)NHC 6 H 4 -2}(CNXy) 2 ]-
TfO (R = H, C(O)Me) 7 were recently reported by us.
Article
X-ray Crystallography. Compounds 1 · 2DMSO,
5·0.5CH 2 Cl 2·0.75Et 2 O, 7a·CHCl 3 , and 10a were measured on a
Bruker Smart APEX machine. Data were collected using monochromated
Mo Kα radiation in ω-scan mode. The structures were
solved by direct methods. The structures were refined anisotropically
on F 2 . The hydrogens of NH 2 or NH were refined freely and were also
refined with DFIX in the compound 1·2DMSO. The ordered methyl
groups were refined using rigid groups (AFIX 137), and the other
hydrogens were refined using a riding model. Special features: for the
compound 5·0.5CH 2 Cl 2·0.75Et 2 O, refinement of the solvent sites
proved difficult. The electron density was over an inversion center.
The molecules at C81 and C71 were interpreted as diethyl ether, and
that at C99 was interpreted as dichloromethane. A system of restraints
was used to improve the stability of the refinement, but the results are
not entirely satisfactory (see, for example, the U values). However, we
prefer this model to the use of SQUEEZE. The xylyl group is
disordered over two positions, ca. 60:40. Further details on crystal
data, data collection, and refinements are summarized in Table 1.
Synthesis of [PdCl 2 {C,N-C(NHXy)C 6 H 4 NH 2 -2}] (1). To a
solution of [Pd{C,N,O-C(NXy)C 6 H 4 {NC(Me)CHC(Me)O}-2}-
(PPh 3 )] (A, Scheme 1; 5 500 mg, 0.75 mmol) in CH 2 Cl 2 (10 mL)
were successively added aqueous HCl (37%, 0.13 mL, 1.51 mmol) and
aqueous H 2 O 2 (35%, 0.20 mL, 2.28 mmol) with a 3.5 h interval, and
the reaction mixture was further stirred for 3 h. The resulting
suspension was filtered, and the solid that was collected was washed
with CH 2 Cl 2 (3 × 5 mL) and dried, first by suction and then in a
vacuum oven (70 °C, 8 h) to give 1 as a white powder. Yield: 291 mg,
0.73 mmol, 96%. Mp: 260 °C dec. 1 H NMR (400 MHz, DMSO-d 6 ,25
°C): δ 2.09 (s, 6 H, Me), 6.27 (d, 1 H, H 4 , 3 J HH = 8 Hz), 6.95 (t, 1 H,
H 6 , 3 J HH = 8 Hz), 7.24 (d, 2 H, m-Xy, 3 J HH = 8 Hz), 7.34 (t, 1 H, p-Xy,
3 J HH = 8 Hz), 7.39 (d, 1 H, H 7 , 3 J HH = 8 Hz), 7.55 (t, 1 H, H 5 , 3 J HH =8
Hz), 7.87 (s br, 2 H, NH 2 ), 11.70 (s br, 1 H, CNHXy). 13 C{ 1 H}
NMR (75.5 MHz, DMSO-d 6 ,25°C): δ 17.5 (Me), 124.5 (C 7 ), 126.6
(C 4 ), 126.9 (C 5 ), 129.1 (m-Xy), 129.4 (p-Xy), 132.1 (o-Xy), 135.6
(C 6 ), 138.2 (C 3 ), 138.3 (ipso-Xy), 153.2 (C 2 ), 204.3 (C 1 ). IR (Nujol,
cm −1 ): ν(NH) 3133, 3118, 3047. Anal. Calcd for C 15 H 16 Cl 2 N 2 Pd: C,
44.86; H, 4.02; N, 6.98. Found: C, 44.85; H, 4.15; N, 6.96. Crystals of
1·2DMSO suitable for an X-ray diffraction study were obtained by
slow diffusion of Et 2 O into a solution of the complex in DMSO.
Synthesis of [PdCl 2 {C(NHXy)C 6 H 4 NH 2 }-2}CN t Bu] (2a). To a
suspension of 1 (100 mg, 0.25 mmol) in CH 2 Cl 2 (10 mL) was added
t BuNC (30 μL, 0.27 mmol). The reaction mixture was stirred for 3 h.
The resulting suspension was filtered. The solid that was collected was
washed with CH 2 Cl 2 (3 × 5 mL) and dried by suction to give
2a·0.5H 2 O as a white powder. Yield: 102 mg, 0.21 mmol, 83%. Mp: 70
°C dec. 1 H NMR (400 MHz, DMSO-d 6 ,25°C): δ 1.16 (s, 9 H,
CMe 3 ), 2.21 (s, 6 H, Me Xy ), 3.84 (v br s, 1 H, H 2 O), 7.17 (“br s”, 3H,
p-Xy + m-Xy), 7.31 (t, 1 H, 3 J HH = 7.6 Hz), 7.37 (d, 1 H, 3 J HH = 7.6
Hz), 7.52 (t, 1 H, 3 J HH = 7.2 Hz), 7.59 (br s, 2 H, NH 2 ), 8.11 (br d, 1
H, 3 J HH = 7.6 Hz); CNHXy not observed. 13 C{ 1 H} NMR (75.5
MHz, DMSO-d 6 ,25°C): δ 18.6 (Me, Xy), 29.1 (Me, CMe 3 ), 57.8 (C,
CMe 3 ), 125.1 (CH), 125.3 (br, CH), 125.9 (C), 126.7 (br, CH), 128.1
(m-Xy + p-Xy), 129.8 (C), 133.3 (v br, CH), 142.7 (C), 147.6 (C), C 1
not observed. IR (Nujol, cm −1 ): ν(NH) 3490, 3421, ν(CN) 2222.
HRMS (ESI, m/z): calcd for C 20 H 24 ClN 3 Pd [M − Cl] 448.0766,
found 448.0765; calcd for C 20 H 24 N 3 Pd [M − 2Cl − H] + 412.1000,
found 412.1008. Anal. Calcd for C 20 H 26 Cl 2 N 3 O 0.5 Pd: C, 48.65; H,
5.31; N, 8.51. Found: C, 48.69; H, 5.50; N, 8.55.
Synthesis of [PdCl 2 {C(NHXy)C 6 H 4 NH 2 }-2}CNXy] (2b). To a
cold suspension of 1 (100 mg, 0.25 mmol) in CH 2 Cl 2 (5 mL, 0 °C)
was added XyNC (44 mg, 0.34 mmol), and the reaction mixture was
stirred in an ice/water bath for 15 min. The resulting suspension was
filtered through a short pad of Celite, and the filtrate was dropped into
rapidly stirred cold Et 2 O (25 mL, 0 °C) to give a pale yellow
suspension, which was filtered. The solid that was collected was
washed with Et 2 O (5 mL) and dried by suction to give 2b·1.25H 2 Oas
a pale yellow solid consisting of an equimolar mixture of cis and trans
isomers. Yield: 91 mg, 0.16 mmol, 65%. Mp: 177 °C. 1 H NMR (400
MHz, CDCl 3 ,25°C, TMS): δ 1.77 (v br s, 2.5 H, H 2 O), 2.17 (s, 6 H,
Xy), 2.38 (s, 6 H, Xy), 6.54 (br s, 1 H), 6.83 (br s, 2 H), 7.02 (br s 2
2698
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
Article
Table 1. Crystal Data and Structure Refinement Details of 1·2DMSO, 5·0.5CH 2 Cl 2·0.75Et 2 O, 7a·CHCl 3 , and 10a
1·2DMSO 5·0.5CH 2 Cl 2·0.75Et 2 O 7a·CHCl 3 10a
formula C 19 H 28 Cl 2 N 2 O 2 PdS 2 C 36.5 H 39.5 Cl 3 N 2 O 4.75 PPd C 28 H 30 C l5 N 3 Pd C 19 H 19 F 3 N 2 O 3 S
fw 557.85 825.92 692.20 412.42
temp (K) 100(2) 100(2) 100(2) 100(2)
cryst syst monoclinic triclinic monoclinic monoclinic
space group P2 1 /c P1̅ P2 1 /n C2/c
a (Å) 17.2928(6) 11.3406(9) 16.0745(7) 17.0508(9)
b (Å) 10.4178(4) 11.5447(9) 11.5809(5) 8.7019(5)
c (Å) 13.6469(5) 14.9407(11) 17.5504(8) 26.1081(14)
α (deg) 90 89.173(2) 90 90
β (deg) 103.161(2) 83.977(2) 115.367(2) 101.108
γ (deg) 90 68.880(2) 90 90
Volume (Å 3 ) 2393.95(15) 1814.1(2) 2952.1(2) 3801.2(4)
Z 4 2 4 8
ρ calcd (Mg m −3 ) 1.548 1.512 1.557 1.441
μ (mm −1 ) 1.190 0.820 1.104 0.222
F(000) 1136 845 1400 1712
cryst size (mm) 0.29 × 0.21 × 0.14 0.17 × 0.13 × 0.13 0.23 × 0.13 × 0.08 0.28 × 0.18 × 0.10
θ range (deg) 2.30−28.21 1.89−28.71 2.18−28.18 2.43−28.22
no. of rflns coll 26 822 22 228 33 470 21 249
no. of indep rflns/R int 55 455/0.0177 8491/0.0197 6875/0.0306 4421/0.0200
transmissn 0.8511/0.7242 0.9008/0.7129 0.9169/0.7853 0.9782/0.8970
no. of restraints/params 0/271 30/446 0/344 3/264
goodness of fit on F 2 1.090 1.157 1.093 1.037
R1 (I >2σ(I)) 0.0202 0.0428 0.0354 0.0449
wR2 (all rflns) 0.0511 0.1002 0.0691 0.1145
largest diff peak/hole (e Å −3 ) 0.386/−0.368 1.137/−0.750 0.641/−0.311 0.600/−0.460
H), 7.18−7.27 (m, 2 H), 7.52−7.67 (m, 4 H), 8.79 (br s, 1 H), 13.92
(v br s, 1H, NH). 1 H NMR (400 MHz, CDCl 3 , −20 °C, TMS): δ 2.17
(s, 6 H, Xy), 2.36 (br s, 6 H, Xy), 6.52 (br s, 1 H), 6.82 (br s, 2 H),
7.02 (m, 2 H), 7.20 (m, 2 H), 7.51 (br s, 1 H), 7.72 (br s, 1 H), 7.98
(br s, 2 H, NH 2 ), 8.82 (br s, 1 H), 13.90 (br s, 1 H, CNHXy).
13 C{ 1 H} NMR (100.8 MHz, CDCl 3 ,25°C, TMS): δ 18.6 (Me), 19.4
(Me), 126.1 (C), 126.8 (CH), 127.8 (CH), 128.0 (CH), 128.2 (CH),
129.1 (CH), 129.7 (CH), 132.5 (C), 134.2 (o-C, Xy), 135.3 (C).
13 C{ 1 H} NMR (100.8 MHz, CDCl 3 , −20 °C, TMS): δ 18.6 (Me),
19.4 (Me), 126.5 (CH), 127.8 (CH), 128.0 (CH), 128.3 (CH), 129.1
(CH), 129.5 (CH), 134.1 (o-C, Xy), 135.1 (C 2 ); C 1 not observed. IR
(Nujol, cm −1 ): ν(NH) 3410, ν(CN) 2203, 2180. Anal. Calcd for
C 24 H 27.5 N 3 O 1.24 PdCl 2 : C, 51.91; H, 4.99; N, 7.57. Found: C, 51.85; H,
5.04; N, 7.53.
Synthesis of [PdCl 2 {C(NHXy)C 6 H 4 NH 2 -2}PPh 3 ] (2c). To a
solution of [Pd{C,N,O-C(NXy)C 6 H 4 {NC(Me)CHC(Me)O}-2}-
(PPh 3 )] (A; 5 300 mg, 0.45 mmol) in a CH 2 Cl 2 /Et 2 O mixture (1/2,
30 mL) was added aqueous HCl (37%, 75 μL, 0.90 mmol), and the
reaction mixture was stirred for 4 h. The resulting suspension was
filtered, and the solid that was collected was dried, first by suction and
then in a vacuum oven (60 °C, 8 h), to give 2c·0.5H 2 O as a deep
yellow solid. Yield: 265 mg, 0.40 mmol, 88%. Mp: 187 °C dec. 1 H
NMR (400 MHz, DMSO-d 6 ,25°C): δ 2.07 (br s, 6 H, Me), 3.50 (br,
1H,H 2 O), 4.88 (d, 1 H, 3 J HH = 8 Hz, H 4 ), 5.50 (t, 1 H, 3 J HH = 7.6 Hz,
H 5 ), 6.75 (d, 1 H, 3 J HH = 8.4 Hz, H 7 ), 6.91 (t, 1 H, 3 J HH = 7.4 Hz, H 6 ),
6.93 (br s, 2 H, NH 2 ), 7.05 (t, 1 H, 3 J HH = 7.4 Hz, p-Xy), 7.39−7.42
(m, 7 H, m-PPh 3 + m-Xy), 7.50 (m, 4 H, 3 J HH = 7.2 Hz, p-PPh 3 + m-
Xy), 7.60 (dd, 6 H, 3 J HH = 7.2 Hz, 3 J HH = 4.4 Hz, o-PPh 3 ), 13.27 (s, 1
H, CNHXy). 13 C{ 1 H} NMR (100.8 MHz, DMSO-d 6 ,25°C): δ
18.23 (Me), 113.2 (C 5 ), 116.4 (C 7 ), 121.0 (br s, o-Xy), 123.8 (C 4 ),
127.6 (p-Xy), 128.1 (m-PPh 3 , 3 J CP = 10.8 Hz), 130.6 (m-Xy + p-PPh 3 ),
130.7 (ipso-PPh 3 , 1 J CP = 52.8 Hz), 132.9 (C 6 ), 134.3 (o-PPh 3 , 2 J CP =
11.2 Hz), 138.1 (C 3 ), 149.0 (C 2 ), 219.0 (C 1 ). 31 P{ 1 H} NMR (162.3
MHz, DMSO-d 6 ,25°C): δ 29.3. IR (Nujol, cm −1 ): ν(NH) 3414,
3324. Anal. Calcd for C 33 H 32 Cl 2 N 2 O 0.5 PPd: C, 58.90; H, 4.79; N, 4.16.
Found: C, 59.06; H, 4.57; N, 4.13.
Synthesis of [PdCl 2 {C(NHXy)C 6 H 4 NH 3 -2}PPh 3 ]Cl (3). To a
solution of [Pd{C,N,O-C(NXy)C 6 H 4 {NC(Me)CHC(Me)O}-2}-
(PPh 3 )] (A; 5 400 mg, 0.59 mmol) in a CH 2 Cl 2 /Et 2 O mixture (1/2,
60 mL) was added aqueous HCl (37%, 0.2 mL, 2.42 mmol). After 4 h
of stirring, the resulting suspension was filtered and the solid that was
collected was dried by suction to give 3 as a white solid. Yield: 408 mg,
0.58 mmol, 98%. Mp: 147 °C dec. The 1 H and 13 C{ 1 H} NMR spectra
of 2c and 3 (400 MHz, DMSO-d 6 ,25°C) are identical except for a
water resonance (from solvent) appearing in the latter at 5.24 ppm as a
broad singlet. IR (Nujol, cm −1 ): ν(NH) 3390. Λ M (cm 2 Ω −1 mol −1 ):
108. Anal. Calcd for C 33 H 31 Cl 2 N 2 PPd: C, 56.59; H, 4.61; N, 4.00.
Found: C, 56.61; H, 4.63; N, 3.83.
Synthesis of SP-4-4-[PdCl{C,N-C(NXy)C 6 H 4 NH 2 -2}CN t Bu]
(4). Solid 2a (31 mg, 0.06 mmol) was heated in a vacuum oven at
70 °C for 7 h to give 4·H 2 O as a pale yellow solid. Yield: 29 mg, 0.06
mmol, 96%. Mp: 212 °C dec. 1 H NMR (300 MHz, DMSO-d 6 ,25°C):
δ 1.15 (s, 9 H, CMe 3 ), 2.10 (s, 6 H, Me Xy ), 4.00 (v br s, 2 H, H 2 O),
6.97−7.07 (m, 3 H, p-Xy + m-Xy), 7.22 (t, 1 H, 3 J HH = 7.4 Hz), 7.28
(br s, 2 H, NH 2 ), 7.31 (d, 1 H, 3 J HH = 7.8 Hz), 7.40 (t, 1 H, 3 J HH = 7.4
Hz), 7.89 (d, 1 H, 3 J HH = 7.8 Hz). 13 C{ 1 H} NMR (75.45 MHz,
DMSO-d 6 ,25°C): δ 18.6 (CMe 3 ), 29.1 (Me Xy ), 54.9 (CMe 3 ), 125.1
(CH), 125.3 (br, CH), 126.8 (br, CH), 128.1 (m-Xy), 129.8 (v br, p-
Xy), 133.4 (v br, o-Xy), 142.8 (v br, C 3 ), 147.6 (v br, C 2 ); ipso-Xy and
C 1 not observed. IR (Nujol, cm −1 ): ν(NH) 3373; ν(CN) 2220.
Anal. Calcd for C 20 H 26 ClN 3 OPd: C, 51.51; H, 5.62; N, 9.01. Found:
C, 51.46; H, 5.59; N, 9.02.
Synthesis of SP-4-4- + SP-4-3-[PdCl{C,N-C(NHXy)C 6 H 4 NH 2 -
2}PPh 3 ] (5). To a suspension of 2c (129 mg, 0.19 mmol) in CH 3 CN
(20 mL) was added AgClO 4 (45 mg, 0.22 mmol). The reaction
mixture was stirred for 14 h and filtered through a short pad of Celite.
The solution was concentrated under vacuum (2 mL), and cold Et 2 O
was added (20 mL, 0 °C). The resulting suspension was stirred for 15
min at 0 °C and then filtered. The solid that was collected was washed
with Et 2 O(3× 5 mL) and dried first by suction and then in a vacuum
oven (70 °C, 12 h) to give 5·0.5H 2 O as a pale yellow solid consisting
of a mixture of the SP-4-4 and SP-4-3 isomers in a 1.22:1 molar ratio.
Yield: 123 mg, 0.17 mmol, 86%. Mp: 198 °C dec. Anal. Calcd for
2699
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
C 33 H 32 Cl 2 N 2 O 4.5 PPd: C, 53.79; H, 4.38; N, 3.80. Found: C, 53.84; H,
4.32; N, 3.74.
Crystals of SP-4-4-[PdCl{C,N-C(NHXy)C 6 H 4 NH 2 -2}-
PPh 3 ]·0.5CH 2 Cl 2·0.75Et 2 O suitable for an X-ray diffraction study
were obtained by slow diffusion of Et 2 O into a solution of the crude
reaction mixture in CH 2 Cl 2 . The crystals were dried in a vacuum oven
(70 °C, 14 h) and used to characterize the pure compound. Mp: 216
°C dec. 1 H NMR (400 MHz, CDCl 3 ,25°C, TMS): δ 2.27 (s, 6 H,
Me), 5.83 (s br, 2 H, NH 2 ), 6.56 (dd, 1 H, 3 J HH = 8.0 Hz, 4 J HH = 0.4
Hz), 6.80 (br d, 1 H, 3 J HH = 3.6 Hz), 6.97 (t, 1 H, 3 J HH = 7.6 Hz), 7.22
(d, 2 H, 3 J HH = 7.6 Hz, m-Xy), 7.34−7.48 (m, 3 H), 7.51−7.58 (m, 9
H, meta + p-PPh 3 ), 7.72−7.77 (m, 6 H, o-PPh 3 ), 11.61 (d br, 1 H, 4 J HP
= 10.4 Hz, CNHXy). 13 C{ 1 H} NMR (100.8 MHz, CDCl 3 ,25°C,
TMS): δ 18.3 (Me), 125.2 (CH), 126.1 (CH), 127.2 (CH), 128.3 (d,
ipso-PPh 3 , 1 J HH = 43.5 Hz), 128.5 (CH), 129.3 (CH), 129.5 (CH),
129.6 (CH), 130.1 (CH), 131.5 (d, p-PPh 3 , 4 J HH = 2.1 Hz), 134.2 (d,
o-PPh 3 , 2 J HH = 11.8 Hz), 136.7 (C), 137.0 (CH), 137.13 (C 3 ), 152.4
(C2), C 1 not observed. 31 P{ 1 H} NMR (162.3 MHz, CDCl 3 ,25°C): δ
36.8. IR (Nujol, cm −1 ): ν(NH) 3229, ν(PdCl) 323.
Synthesis of SP-4-3-[PdCl{C,N-C(NHXy)C 6 H 4 NH 2 -2}PPh 3 ].
The NMR and IR data for this compound were obtained from the
crude reaction mixture. 1 H NMR (400 MHz, CDCl 3 ,25°C, TMS): δ
1.66 (s, 6 H, Me), 1.71 (br, 1 H, H 2 O), 6.30 (d, 1 H, 3 J HH = 8.0 Hz),
6.85 (s br, 2 H, NH 2 , overlapped with resonances from the minor
isomer), 6.93 (d, 2 H, 3 J HH = 7.6 Hz, m-Xy), 7.14 (t, 1 H, 3 J HH = 7.6
Hz, p-Xy), 7.33−7.49 (various m, 3 H, overlapped with resonances
from the minor isomer), 7.55 (m, 9 H, m- +p-PPh 3 , overlapped with
those from the minor isomer), 7.82 (dd, 6 H, 3 J HH = 7.6 Hz, 3 J HH = 4.4
Hz, o-PPh 3 ), 8.69 (s br, 1 H, NH=C). 31 P{ 1 H} NMR (162.3 MHz,
CDCl 3 ,25°C): δ 16.0. IR (Nujol, cm −1 ): ν(NH) 3229, ν(PdCl) 256.
Synthesis of SP-4-4- +SP-4-3-[PdCl{C,N-C(NHXy)C 6 H 4 NH 2 -
2}(PPh 3 )](TfO) (5′). To a suspension of 2c (80 mg, 0.12 mmol) in
CH 2 Cl 2 (10 mL) was added TlTfO (40 mg, 0.11 mmol). The reaction
mixture was stirred for 30 min and then filtered through a short pad of
Celite. The solution was concentrated under vacuum (1 mL), and cold
Et 2 O was added (20 mL, 0 °C). The resulting suspension was stirred
for 15 min at 0 °C and then filtered. The collected solid was washed
with Et 2 O(3× 5 mL) and dried first by suction and then in an oven
under vacuum (70 °C) for 7 h to give 5′ as a yellow solid consisting of
a mixture of the SP-4-4 and SP-4-3 isomers in a 1.33:1 molar ratio.
Yield: 60 mg, 0.08 mmol, 64%. Mp: 183 °C dec. 1 H NMR (400 MHz,
CDCl 3 ,25°C, TMS): δ 1.66 (s, 6 H, Me, minor isomer), 2.25 (s, 6 H,
Me, major isomer), 6.20 (s br, 2 H, NH 2 , major isomer), 6.25 (d, 1 H,
3 J HH = 8.0 Hz, minor isomer), 6.55 (d, 1 H, 3 J HH = 8.0 Hz, major
isomer), 6.80 (t, 1 H, 3 J HH = 7.6 Hz, minor isomer) 6.92−6.97 (m, 2
H, 1H (major isomer) + 1H (minor isomer)), 7.08 (br s, 2 H, NH 2 ,
minor isomer), 7.13 (t, 1 H, 3 J HH = 7.2 Hz, major isomer), 7.21 (d, 2
H, 3 J HH = 7.2 Hz, m-Xy, major isomer), 7.33 (d, 2 H, 3 J HH = 7.6 Hz, m-
Xy, minor isomer), 7.35−7.46 (m, 4 H, 2H (major isomer) + 2H
(minor isomer)), 7.55 (m, 18 H, m- + p-PPh 3 , major + minor
isomers), 7.69−7.66 (m, 6 H, o-PPh 3 , major isomer), 7.81 (dd, 6 H,
3 J HH = 7.6 Hz, 4 J HH = 4.0 Hz, o-PPh 3 , minor isomer), 8.85 (s br, 1 H,
CNHXy, minor isomer), 11.60 (d br, 1 H, 4 J HP = 11.0 Hz, C
NHXy, major isomer). 31 P{ 1 H} NMR (162.3 MHz, CDCl 3 ,25°C): δ
16.2 (minor isomer), 36.2 (major isomer). Anal. Calcd for
C 34 H 31 ClF 3 N 2 O 3 PPdS: C, 52.52; H, 4.02; N, 3.60; S, 4.12. Found:
C, 52.56; H, 3.79; N, 3.50; S, 3.95. IR (Nujol, cm −1 ): ν(NH) 3312,
ν(PdCl) 333, 260.
Synthesis of [Pd 2 Cl 2 {μ-N,C,N′-C(NXy)C 6 H 4 NH 2 -2} 2 ] (6a). To
a suspension of 1 (115 mg, 0.29 mmol) in CHCl 3 (10 mL) was added
NEt 3 (80 μL, 0.57 mmol). The reaction mixture was stirred for 3 h and
then filtered. The solid collected was washed successively with CHCl 3
(3 × 5 mL) and methanol (3 × 3 mL) and dried, first by suction and
then in an oven under vacuum (70 °C, 6 h), to give 6a as a yellow
solid. Yield: 97 mg, 0.13 mmol, 93%. Mp: 273 °C dec. 1 H NMR (400
MHz, DMSO-d 6 ,25°C): δ 1.73 (s, 3 H, Me), 2.51 (s, 3 H, Me), 5.79
(d, 1 H, 3 J HH = 7.2 Hz), 6.63 (t, 1 H, 3 J HH = 6.4 Hz), 6.73 (d, 1 H, 3 J HH
= 6.8 Hz), 6.79 (d, 1 H, 2 J HH = 10.8 Hz, NH), 6.94 (t, 1 H, 3 J HH = 6.8
Hz), 7.01 (d, 1 H, 3 J HH = 6.4 Hz), 7.13 (t, 1 H, 3 J HH = 6.8 Hz), 7.19
(d, 1 H, 3 J HH = 7.2 Hz), 7.38 (br d, 1 H, 2 J HH = 10.8 Hz, N−H···Cl).
2700
Article
13 C{ 1 H} NMR (100.8 MHz, DMSO-d 6 ,25°C): δ 18.6 (Me), 19.3
(Me) 122.3 (C 4 ), 124.5 (C 7 ), 125.2 (C 5 ), 125.4 (p-Xy), 127.7 (m-Xy),
128.4 (m-Xy), 129.7 (o-Xy), 130.2 (o-Xy), 130.3 (C 6 ), 141.9 (ipso-Xy),
147.0 (C 3 ), 147.1 (C 2 ), 203.6 (C 1 ). IR (Nujol, cm −1 ): ν(NH) 3187,
3162. Anal. Calcd for C 30 H 30 Cl 2 N 4 Pd 2 : C, 49.34; H, 4.14; N, 7.67.
Found: C, 48.90; H, 4.03; N, 7.48.
Synthesis of [Pd 2 (OAc) 2 {μ-N,C,N′-C(NXy)C 6 H 4 NH 2 -2} 2 ]
(6b). To a suspension of 6a (110 mg, 0.15 mmol) in acetone (15
mL) was added TlTfO (110 mg, 0.31 mmol). The reaction mixture
was stirred for 1.5 h and then filtered through a short pad of Celite.
Then, to the filtered solution was added NaOAc (30 mg, 0.37 mmol)
and the reaction mixture was then stirred for 4 h. The resulting
suspension was filtered through a short pad of Celite. The resulting
solution was concentrated under vacuum (2 mL), and Et 2 O was added
(20 mL) to give a suspension, which was filtered. The collected solid
was washed first with Et 2 O(3× 5 mL) and then dried first by suction
and then in an oven under vacuum (70 °C, 6 h) to give 6b as a pale
yellow solid. Yield: 111 mg, 0.14 mmol, 94%. Mp: 258 °C dec. 1 H
NMR (400 MHz, DMSO-d 6 ,25°C): δ 1.29 (s, 3 H, Ac), 1.69 (s, 3 H,
Me Xy ), 2.61 (s, 3 H, Me Xy ), 5.98 (d, 1 H, 3 J HH = 8 Hz), 6.73 (t, 1 H,
3 J HH = 8 Hz), 6.85 (d, 1 H, 3 J HH = 8 Hz), 7.01−7.18 (m, 6 H), 7.25 (t,
1H, 3 J HH = 8 Hz), 8.74 (br d, 2 H, 2 J HH = 10 Hz, N−H···OAc). IR
(Nujol, cm −1 ): ν(NH) 3252, 3489. Anal. Calcd for C 34 H 36 N 4 O 4 Pd 2 :
C, 52.52; H, 4.67; N, 7.21. Found: C, 52.21; H, 4.44; N, 6.89.
Synthesis of cis-[PdCl 2 {C,N-C(NXy)CMe 2 NHC 6 H 4 -2}L] (L =
XyNC (7a), PPh 3 (7b)). To a suspension of 1 (for 7a, 77 mg, 0.19
mmol; for 7b, 70 mg, 0.17 mmol) in acetone (15 mL) was added the
appropriate ligand (for 7a, XyNC, 27.2 mg, 0.21 mmol; for 7b, PPh 3 ,
50 mg, 0.19 mmol). After 2.5 (7a) or4h(7b) of stirring, the resulting
suspension was filtered and the solid collected was washed successively
with acetone (3 × 3 mL). 7b was additionally washed with CH 2 Cl 2 (3
× 3 mL). The solid was dried by suction and, in the case of 7b, ina
vacuum oven (70 °C, 7 h).
Data for 7a are as follows. Deep yellow solid. Yield: 79 mg, 0.14
mmol, 72%. Mp: 206 °C dec. 1 H NMR (400 MHz, DMSO-d 6 ,25°C):
δ 1.34 (br s, 3 H, CMe 2 ), 1.51 (br s, 3 H, CMe 2 ), 1.82 (s, 3 H, Me,
Xy q ), 1.96 (s, 6 H, Me, Xy Pd ), 2.67 (s, 3 H, Me, Xy q ), 6.92 (d, 1 H,
3 J HH = 8 Hz, H 4 ), 7.02−7.08 (m, 2 H), 7.20 (d, 2 H, 3 J HH = 8 Hz, m-
Xy Pd ), 7.30−7.38 (m, 3 H), 7.52−7.56 (m, 1 H), 8.25 (s, 1 H, NH),
8.70 ppm (d, 1 H, 3 J HH = 7 Hz, H 7 ). IR (Nujol, cm −1 ): ν(NH) 3259,
ν(CN) 2184. Anal. Calcd for C 28 H 30 Cl 5 N 3 Pd: C, 48.58; H, 4.37; N,
6.07. Found: C, 48.19; H, 4.39; N, 6.09. Crystals of 7a·CHCl 3 suitable
for an X-ray diffraction study were obtained by slow evaporation of a
solution of the complex in CHCl 3 and were also used to get the
elemental analyses, melting point, and IR spectrum.
Data for 7b·H 2 O·Me 2 CO are as follows. Yellow solid. Yield: 109
mg, 0.14 mmol, 81%. Mp: 202 °C dec. 1 H NMR (400 MHz, DMSOd
6 ,25°C): δ 0.80 (s, 3 H, Me), 1.14 (br s, 3 H, Me Xy ), 1.49 (br s, 3 H,
Me Xy ), 2.07 (s, 6 H, Me, Me 2 CO), 2.86 (s, 3 H, Me), 3.35 (br s, 1 H,
H 2 O), 6.81−6.91 (m, 4 H), 7.11−7.48 (various m, 16 H), 8.00 (s, 1 H,
NH), 8.94 (d, 1 H, 3 J HH = 8.0 Hz). 31 P{ 1 H} NMR (162.3 MHz,
DMSO-d 6 ,25°C): δ 22.3. IR (Nujol, cm −1 ): ν(NH) 3276. Anal. Calcd
for C 39 H 42 Cl 2 N 2 O 1.5 PPd: C, 60.75; H, 5.49; N, 3.63. Found: C, 60.77;
H, 5.76; N, 3.71.
Synthesis of cis-[PdCl 2 {C,N-C(NXy)CH(Me)NHC 6 H 4 -2}PPh 3 ]
(8a). To a suspension of 1 (90 mg, 0.22 mmol) in CH 2 Cl 2 (5 mL)
were successively added MeCHO (100 μL, 1.77 mmol) and PPh 3 (70
mg, 0.27 mmol), and the reaction mixture was stirred for 12 h. The
resulting suspension was filtered, and the solid that was collected was
washed with CH 2 Cl 2 (3 × 5 mL) and dried, first by suction and then
in a vacuum oven (70 °C, 7 h), to give 8a as a deep yellow solid
consisting of a mixture of two isomers in a 2.3:1 molar ratio. Yield: 138
mg, 0.16 mmol, 71%. Mp: 203 °C. 1 H NMR (300 MHz, DMSO-d 6 ,25
°C): major isomer, δ 0.96 (s, 3 H, Me Xy ), 1.30 (d, 3 H, 3 J HH = 6.0 Hz,
CHMe), 2.93 (s, 3 H, Me Xy ), 4.74 (dq, 1 H, 3 J HH = 6.3 Hz, 4 J HH = 1.5
Hz, CHMe), 6.77−6.92 (m obscured by the resonances of the minor
isomer, 3 H), 6.98 (d, 2 H, 3 J HH = 6.0 Hz, m-Xy), 7.01−7.61 (several
m obscured by the resonances of the minor isomer, 16 H), 7.83 (br d
overlapped with that corresponding to the minor isomer, 1 H, 3 J HH =
4.5 Hz, NH), 9.02 (d, 1 H, 3 J HH = 7.8 Hz); minor isomer, δ 1.03 (d, 3
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
H, 3 J HH = 6.0 Hz, CHMe), 1.11 (s, 3 H, Me Xy ), 2.62 (s, 3 H, Me Xy ),
5.10 (m, 1 H, CHMe), 6.77−6.92 (m obscured by the resonances of
the major isomer, 3 H), 7.07 (d, 2 H, 3 J HH = 6.0 Hz, m-Xy), 7.01−7.61
(several m obscured by the resonances of the major isomer, 16 H, 7.83
(br s overlapped with that NH corresponding to the major isomer, 1
H, NH), 8.89 (d, 1 H, 3 J HH = 8.1 Hz). 13 C{ 1 H} NMR (75.5 MHz,
DMSO-d 6 ,25°C): major isomer, δ 17.0 (Me), 18.4 (Me), 22.2 (Me),
19.4 (Me), 69.6 (CHMe), 115.0 (CH), 117.3 (CH), 123.8 (C), 128.3
(CH), 128.0 (CH), 128.2 (d overlapped with that from the minor
isomer, J = 10 Hz, m-PPh 3 ), 129.3 (s, p-PPh 3 ), 130.1 (CH), 130.6 (br
s overlapped with that from the minor isomer, o-PPh 3 ), 133.6 (o-Xy),
136.3 (CH), 136.3 (C), 140.3 (CH), 140.9 (C), 210.3 (CN); ipso-
PPh 3 and ipso-XyNC resonances not observed; minor isomer, δ 9.1
(Me), 16.0 (Me), 21.0 (Me), 19.4 (Me), 69.4 (CHMe), 114.7 (CH),
118.3 (CH), 125.4 (C), 128.2 (d overlapped with that from the major
isomer, J = 10 Hz, m-PPh 3 ), 128.9 (s, p-PPh 3 ), 129.4 (CH), 130.6 (br s
overlapped with that from the major isomer, o-PPh 3 ), 130.8 (br s, o-
PPh 3 ), 134.3 (CH), 134.5 (CH), 134.6 (CH), 137.6 (o-Xy), 139.2
(CH), 141.8 (C), 141.3 (C), 210.2 (CN); ipso-PPh 3 and ipso-XyNC
resonances not observed. 31 P{ 1 H} NMR (121.5 MHz, DMSO-d 6 ,25
°C): δ 23.0 (major isomer), 23.1 (minor isomer). IR (Nujol, cm −1 ):
ν(NH) 3262, 3204. Anal. Calcd for C 35 H 33 Cl 2 N 2 PPd: C, 60.93; H,
4.82; N, 4.06. Found: C, 60.71; H, 5.01; N, 3.95.
Synthesis of cis-[PdCl 2 {C,N-C(NXy)CH(To)NHC 6 H 4 -2}PPh 3 ]
(8b). To a suspension of 1 (50 mg, 0.12 mmol) in CH 2 Cl 2 (10 mL)
were successively added ToCHO (100 μL, 0.85 mmol) and PPh 3 (50
mg, 0.19 mmol). The reaction mixture was stirred for 48 h at room
temperature. The resulting suspension was concentrated under
vacuum to 5 mL, cooled to 0 °C, and then filtered. The solid that
was collected was washed with CH 2 Cl 2 (3 × 5 mL) and dried first by
suction and then in an oven under vacuum (70 °C, 14 h) to give
8b·2H 2 O as a deep yellow solid consisting of a mixture of two isomers
in a 4:1 molar ratio. Yield: 63 mg, 0.08 mmol, 63%. Mp: 188 °C. 1 H
NMR (300 MHz, DMSO-d 6 ,25°C): major isomer, δ 1.13 (s, 3 H, Me,
Xy), 2.24 (s, 3 H, Me, Xy or To), 2.27 (s, 3 H, Me, Xy or To), 3.33 (br
s, 4 H, H 2 O), 5.85 (d, 1 H, 3 J HH = 3.3 Hz, H 8 ), 6.73−7.06 (various m
obscured by those of the minor isomer, 7 H), 7.15−7.63 (m obscured
by those of the minor isomer, 18 H), 8.23 (br d, 1 H, 3 J HH = 4.2 Hz,
NH), 9.06 (d, 1 H, 3 J HH = 7.8 Hz, H 7 ); minor isomer, δ 1.16 (s, 3 H,
Me, Xy), 2.14 (s, 3 H, Me, To), 2.60 (s, 3 H, Me, Xy), 5.89 (br s, 1 H,
H 8 ), 6.73−7.06 (various m obscured by those of the minor isomer, 7
H), 7.15−7.63 (m obscured by those of the minor isomer, 18 H), 7.91
(br s, 1 H, NH), 9.83 (d, 1 H, 3 J HH = 7.8 Hz, H 7 ). 31 P{ 1 H} NMR
(121.5 MHz, DMSO-d 6 ,25°C): major isomer, δ 23.8; minor isomer, δ
23.3. IR (Nujol, cm −1 ): ν(NH) 3245, 3271. Anal. Calcd for
C 41 H 41 Cl 2 N 2 O 2 PPd: C, 61.40; H, 5.15; N, 3.49. Found: C, 61.64;
H, 5.07; N, 3.27.
Synthesis of cis-[PdCl 2 {C,N-C(NXy)CH(CHCH 2 )NHC 6 H 4 -
2}PPh 3 ] (8c). To a suspension of 1 (90 mg, 0.22 mmol) in CH 2 Cl 2
(5 mL) was successively added CH 2 CHC(O)H (100 μL, 1.50
mmol) and PPh 3 (70 mg, 0.27 mmol). The reaction mixture was
stirred overnight at room temperature. The resulting suspension was
filtered through a short pad of Celite and concentrated under vacuum
to 1 mL, and then cool Et 2 O was added (20 mL, 0 °C). The resulting
suspension was stirred at 0 °C for 15 min and then filtered. The
collected solid was washed with Et 2 O(3× 5 mL) and dried first by
suction and then in an oven under vacuum (40 °C) overnight to give
8c as a dark yellow solid consisting of a mixture of two isomers in a
1.33:1 molar ratio. Yield: 116 mg, 0.18 mmol, 82%. Mp: 174 °C dec.
1 H NMR (400 MHz, DMSO-d 6 ,25°C): 1.06 (s, 3 H, Xy, minor
isomer), 1.69−1.96 (v br s, 1 H, H 2 O), 1.89 (br s, 6 H, Xy, major +
minor isomers), 2.73 (s, 3 H, Xy, major isomer), 3.15 (“q” 2H, 3 J HH =
12.4 Hz, H E or Z , minor isomer), 4.08 (“q”, 2H, 3 J HH = 13.2 Hz, H E or Z ,
major isomer), 5.20 (m, 1 H, H 8 , major isomer), 6.72−6.95 (m, 10 H,
major + minor isomers), 6.95−7.40 (m, 22 H, major + minor
isomers), 7.57−7.76 (m, 16 H, major + minor isomers), 8.81 (br s, 1
H, NH, major isomer), 9.14 (dd, 1 H, 3 J HH = 8.0 Hz, 4 J HH = 1.2 Hz,
H 7 , major isomer). 31 P{ 1 H} NMR (162.3 MHz, DMSO-d 6 ,25°C): δ
23.8 (minor isomer), 23.9 (major isomer). IR (Nujol, cm −1 ): ν(NH)
Article
3158 (w, v br). Anal. Calcd for C 36 H 34 Cl 2 N 2 O 0.5 PPd: C, 60.82; H,
4.82; N, 3.94. Found: C, 60.59; H, 5.07; N, 3.76.
Synthesis of [{cis-PdCl 2 {C(NXy)CHNHC 6 H 4 -2}(CNXy)} 3 {μ 3 -
C 6 H 3 (C 6 H 4 -4) 3 -1,3,5}] (9). To a suspension of 1 (120 mg, 0.30
mmol) in CH 2 Cl 2 (15 mL) were successively added C 6 H 3 (C 6 H 4 CHO-
4) 3 -1,3,5 (35 mg, 0.09 mmol) and XyNC (43 mg, 0.33 mmol), and the
reaction mixture was stirred for 5 h. The resulting solution was filtered
through a short pad of anhydrous MgSO 4 and concentrated under
vacuum (1 mL), and cold Et 2 O was added (20 mL, 0 °C). The
resulting suspension was stirred at 0 °C for 15 min and then filtered.
The solid collected was recrystallized from a cold CH 2 Cl 2 /Et 2 O
mixture (1:10, 22 mL, 0 °C), washed with cold Et 2 O(3× 5 mL, 0
°C), and dried by suction to give 9 as a yellow solid. Yield: 116 mg,
0.06 mmol, 60%. Mp: 222 °C dec. 1 H NMR (400 MHz, DMSO-d 6 ,25
°C): δ 2.04 (br s, 27 H, Me), 2.17 (br s, 27 H, Me), 2.30 (br s, 18 H,
Me), 6.37−7.97 (several m, 94 H), 8.93 (br s, 6 H, NH RRR/SSS+RRS/SSR ),
10.06 (br s, 2 H, NH NH RRR/SSS+RRS/SSR ), 10.47 (br s, 1 H, NH
NH RRR/SSS or RRS/SSR ), 11.73 (br s, 1 H, NH NH RRR/SSS or RRS/SSR ). IR
(Nujol, cm −1 ): ν(NH) 3215, ν(CN) 2191. Anal. Calcd for
C 99 H 87 Cl 6 N 9 Pd 3 : C, 61.46; H, 4.53; N, 6.52. Found: C, 61.37; H,
4.68; N, 6.58.
Synthesis of 2-Methyl-4-xylyliminium-1,4-dihydroquinoline
Triflate (10a). To a solution of trans-[PdI{C(NXy)-
CMe 2 NHC 6 H 4 -2}(CNXy) 2 ]TfO 7 (180 mg, 0.20 mmol) in acetone
(20 mL) was added TlTfO (70 mg, 0.20 mmol) in a Carius tube. The
tube was sealed, and the resulting suspension was stirred overnight at
130 °C. The black suspension was filtered through a short pad of
anhydrous MgSO 4 . The solution was concentrated to dryness and
extracted with a 1:30 mixture of CH 2 Cl 2 and Et 2 O(3× 15.5 mL). The
extract was concentrated to dryness to give a brown oily residue, which
was dissolved in CHCl 3 (1 mL) and layered with Et 2 O (20 mL). 10a
crystallized as light brown crystals after cooling the mixture to −34 °C
overnight. Yield: 59 mg, 0.14 mmol, 73%. Mp: 198 °C dec. 1 H NMR
(400 MHz, CDCl 3 ,25°C, TMS): δ 2.17 (s, 6 H, Me Xy ), 2.54 (s, 3 H,
Me), 5.81 (d, 1 H, CH, 4 J HH = 1.2 Hz), 7.14 (d, 2 H, 3 J HH = 7.6 Hz,
m-Xy), 7.22 (“dt”, 1H, 3 J HH = 7.2 Hz, 4 J HH = 1.2 Hz, p-Xy), 7.60 (t, 1
H, 3 J HH = 7.2 Hz), 7.75 (“dt”, 1H, 3 J HH = 7.6 Hz, 4 J HH = 1.0 Hz), 8.00
(d, 1 H, 3 J HH = 8.0 Hz), 8.58 (d, 1 H, 3 J HH = 8.4 Hz), 9.08 (s, 1 H,
NH), 12.66 (br s, 1 H, NHXy). 13 C{ 1 H} NMR (100.8 MHz, CDCl 3 ,
25 °C, TMS): δ 17.8 (Me, Xy), 20.3 (Me), 98.9 (CH, CH), 115.6
(CH), 120.3 (CH), 120.4 (q, 1 J CF = 320 Hz, CF 3 SO 3 ), 121.9 (CH),
127.1 (CH), 128.3 (CH), 128.9 (CH, m-Xy), 133.4 (C), 133.8 (CH),
136.1 (o-Xy), 138.5 (C), 154.3 (C), 155.6 (C). IR (Nujol, cm −1 ):
ν(NH) 3294, 3183. Anal. Calcd for C 19 H 19 F 3 N 2 SO 3 : C, 55.33; H,
4.64; N, 6.79; S, 7.77. Found: C, 54.97; H, 4.75; N, 6.93; S, 7.68.
HRMS (ESI, m/z): calcd for C 18 H 19 N 2 [M] + , 263.1543; found,
263.1550. Crystals of 10a suitable for an X-ray diffraction study were
obtained by slow diffusion of Et 2 O into a solution of the product in
CHCl 3 .
Synthesis of 2-Methyl-3-methoxycarbonyl-4-xylyliminium-
1,4-dihydroquinoline Triflate (10b). A solution of trans-[PdI{C-
(NXy)C(Me)(CH 2 C(O)Me)NHC 6 H 4 -2}(CNXy) 2 ]TfO 7 (200 mg,
0.21 mmol) in acetone (20 mL) was prepared in a Carius tube. TlTfO
(80 mg, 0.23 mmol) was added, the tube was sealed, and the resulting
suspension was stirred at 130 °C for 12 h. The black suspension was
filtered through a short pad of anhydrous MgSO 4 , the solution was
concentrated under vacuum (1 mL), and cold Et 2 O was added (20
mL, 0 °C). The resulting suspension was filtered, and the solid that
was collected was washed with Et 2 O(3× 5 mL) and dried by suction
to give 10b·H 2 O as a white powder. Yield: 49 mg, 0.10 mmol, 49%.
Mp: 98 °C. 1 H NMR (400 MHz, DMSO-d 6 ,25°C): δ 1.58 (v br s, 2
H, H 2 O), 2.28 (s, 6 H, Me Xy ), 2.79 (s, 3 H, Me), 2.82 (s, 3 H, Me),
7.15 (“s”, 3H,m-Xy + p-Xy), 7.65 (“s”, 1 H), 7.86 (t, 1 H, 3 J HH = 7.6
Hz), 8.44 (d, 1 H, 3 J HH = 8.0 Hz), 8.68 (d, 1 H, 3 J HH = 7.2 Hz), 12.13
(v br s, 1 H, NH); NHXy not observed. 1 H NMR (400 MHz, acetoned
6 ,25°C): δ 2.29 (s, 6 H, Me Xy ), 3.12 (s, 3 H, Me), 3.14 (s, 3 H, Me),
7.20 (“s”,3H,m-Xy + p-Xy), 8.11−8.19 (m, 2 H), 8.80 (d, 1 H, 3 J HH =
8.4 Hz), 9.11 (d, 1 H, 3 J HH = 7.2 Hz), 10.27 (br s, 1 H, NH), 16.45 (v
br s, 1 H, NHXy). 13 C{ 1 H} NMR (100.8 MHz, DMSO-d 6 ,25°C): δ
18.5 (Me), 19.1 (Me), 120.6 (q, 1 J CF = 322 Hz, CF 3 SO 3 ), 123.6 (CH),
2701
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
126.2 (CH), 126.6 (CH), 126.7 (C), 127.9 (CH), 129.0 (CH), 132.9
(CH), 134.7 (C), 135.1 (C), 158.4 (C), 164.0 (C). IR (Nujol, cm −1 ):
ν(NH) 3370. Anal. Calcd for C 21 H 23 F 3 N 2 O 5 S: C, 53.38; H, 4.91; N,
3.93; S, 6.79. Found: C, 53.48; H, 4.62; N, 5.72; S, 6.46. HRMS (ESI,
m/z): calcd for C 20 H 21 N 2 O [M] + , 305.1648; found, 305.1657.
Synthesis of 2,2-Dimethyl-3-xylyl-4-phenylethynyl-1,2-dihydroquinazolinium
Triflate (11). To a solution of trans-[PdI{C(
NXy)CMe 2 NHC 6 H 4 -2}(CNXy) 2 ]TfO 7 (400 mg, 0.44 mmol) in
CH 2 Cl 2 (20 mL) were successively added PhCCH (50 μL, 0.46
mmol), CuI (85 mg, 0.45 mmol), and Et 3 N (62 μL, 0.45 mmol). After
48 h or stirring at room temperature, the reaction mixture was filtered
through anhydrous MgSO 4 . The filtrate was concentrated (1 mL), and
cold Et 2 O was added (20 mL, 0 °C). The resulting suspension was
filtered, and the solid that was collected was dissolved in CH 2 Cl 2 (1
mL) and chromatographed on silica gel (60 Å, 70−220 mesh) with 5%
fluorescent GF 254 and CH 2 Cl 2 as eluent. The appropriate band (R f =
0.60) was collected and concentrated under vacuum to 1 mL. Cold
Et 2 O (20 mL, 0 °C) was added, the resulting suspension was filtered,
and the solid that was collected was dried first by suction an then in an
oven at 40 °C for 8 h to give 11 as a red solid. Yield: 154 mg, 0.30
mmol, 67%. Mp: 134 °C dec. 1 H NMR (400 MHz, CDCl 3 ,25°C,
TMS): δ 1.72 (s, 6 H, CMe 2 ), 2.33 (s, 6 H, Me), 6.99 (“q”,2H, 3 J HH =
7.8 Hz), 7.13 (d, 2 H, 3 J HH = 7.2 Hz), 7.29 (d, 2 H, 3 J HH = 7.6 Hz),
7.36−7.40 (m, 2 H), 7.44 (d, 1 H, 3 J HH = 7.8 Hz), 7.51 (t, 1 H, 3 J HH =
7.2 Hz), 7.63 (“dt”, 1H, 3 J HH = 7.6 Hz, 4 J HH = 1.2 Hz), 7.81 (t, 1 H,
3 J HH = 7.8 Hz), 8.83 (s br, 1 H, NH). 13 C{ 1 H} NMR (75.5 MHz,
CDCl 3 ,25°C, TMS): δ 18.7 (Me Xy ), 24.4 (CMe 2 ), 65.6 (CCPh),
75.8 (CMe 2 ), 80.8 (CCPh), 112.9 (C), 118.1 (C), 118.3 (CH),
120.4 (CH), 128.8 (CH), 129.4 (CH), 130.1 (CH), 130.2 (CH),
132.5 (CH), 133.1 (CH), 135.5 (o-Xy), 138.7 (C), 140.6 (CH), 148.1
(C), 150.1 (C). IR (Nujol, cm −1 ): ν(CC) 2199. Anal. Calcd for
C 27 H 25.5 F 3 N 2 O 3.25 S: C, 62.48; H, 4.95; N, 5.40; S, 6.18. Found: C,
62.51; H, 4.73; N, 5.48; S, 6.02. Alternatively, 11 could be isolated in
74% yield from the reaction of 12 (200 mg, 0.49 mmol) with TfOH
(50 μL, 0.57 mmol) (1.5 h at room temperature in acetone, 5 mL)
upon filtering the reaction mixture through a short pad of anhydrous
MgSO 4 , concentrating (1 mL), and precipitating with cold Et 2 O (20
mL, 0 °C).
Synthesis of H 2 NC 6 H 4 {C(NXy)CCPh}-2 (12). To a suspension
of [PdI{C(NXy)C 6 H 4 NH 2 -2}(CNXy) 2 ] 7 (900 mg, 1.25
mmol) in anhydrous acetonitrile (30 mL) was added AgTfO (322
mg, 1.25 mmol) under a nitrogen atmosphere. The reaction mixture
was stirred at room temperature for 1.5 h and then filtered through
anhydrous MgSO 4 under a nitrogen atmosphere. The resulting
solution was concentrated under vacuum to 0.5 mL, and anhydrous
THF (10 mL) was added. To the solution were successively added
PhCCH (138 μL, 1.26 mmol) and NEt 3 (175 μL, 1.26 mmol)
under a nitrogen atmosphere. After 5 h of stirring, the suspension was
concentrated under vacuum to dryness to give a black oily residue,
which was treated with an Et 2 O/n-hexane mixture (1:10, 3 × 11 mL).
The combined extracts were filtered through anhydrous MgSO 4 , and
the resulting solution was concentrated under vacuum to dryness to
give 12 as a red solid. Yield: 332 mg, 1.02 mmol, 82%. Mp: 83 °C. 1 H
NMR (400 MHz, CDCl 3 ,25°C, TMS): δ 2.13 (s, 6 H, Me), 6.69 (br
s, 2 H, NH 2 ), 6.75 (d, 1 H, 3 J HH = 8.0 Hz), 6.77 (“dt”, 1H, 3 J HH = 8.0
Hz, 4 J HH = 0.8 Hz), 7.00 (t, 1 H, 3 J HH = 7.6 Hz), 7.10 (m, 4 H), 7.22−
7.37 (m, 4 H), 8.11 (dd, 1 H, 3 J HH = 8.0 Hz, 4 J HH = 1.2 Hz). 13 C{ 1 H}
NMR (100.8 MHz, CDCl 3 ,25°C, TMS): δ 18.2 (Me), 82.6 (C
CPh), 97.7 (CCPh), 115.8 (CH), 116.5 (CH), 117.3 (C), 121.3
(C), 123.4 (CH), 127.0 (o-Xy), 127.6 (CH), 128.3 (CH), 129.6 (CH),
131.8 (CH), 132.3 (CH), 132.9 (CH), 149.2 (C), 150.1 (C), 154.6
(C). IR (Nujol, cm −1 ): ν(NH) 3443; ν(CC) 2201. Anal. Calcd for
C 23 H 20 N 2 : C, 85.15; H, 6.21; N, 8.63. Found: C, 84.97; H, 6.13; N,
8.57. Alternatively, 12 was isolated (89% yield) from the reaction of
[PdI{C(NXy)C 6 H 4 NH 2 -2}(CNXy) 2 ] (540 mg, 0.75 mmol) with
PhCCH (85 μL, 0.77 mmol), CuI (150 mg, 0.79 mmol), and Et 3 N
(110 μL, 0.79 mmol) (in CH 2 Cl 2 , 20 mL, at room temperature
overnight). The reaction mixture was filtered through Celite, the
filtrate was concentrated (1 mL) and chromatographed on silica gel
(60 Å, 70−220 mesh) with 5% fluorescent GF 254 and CH 2 Cl 2 as
2702
Article
eluent, and the appropriate band (R f = 0.80) was collected and
concentrated under vacuum to dryness.
Synthesis of [Pd 2 {μ-C,N-C(NXy)C 6 H 4 NH-2}{C,N-C(NXy)-
C 6 H 4 NH 2 -2}(CNXy) 3 ] (13). To a solution of [PdI{C(NXy)-
C 6 H 4 NH 2 -2}(CNXy) 2 ] 7 (260 mg, 0.36 mmol) in CH 2 Cl 2 (15 mL)
was added K t BuO (50 mg, 0.45 mmol). The reaction mixture was
stirred for 3 h and then filtered through a short pad of Celite. The
resulting solution was concentrated under vacuum (1 mL), n-pentane
was added (20 mL), the suspension was filtered, and the solid that was
collected was washed with n-pentane (3 × 5 mL) and dried, first by
suction and then in an oven under vacuum (70 °C, 6 h), to give
13·1.5H 2 O as an orange solid. Yield: 148 mg, 0.14 mmol, 76%. Mp:
182 °C dec. 1 H NMR (400 MHz, CDCl 3 ,25°C, TMS): δ 1.57 (br s, 6
H, Me + H 2 O), 1.59 (s, 3 H, Me) 1.93 (s, 12 H, Me), 2.06 (s, 3 H,
Me), 2.38 (s, 3 H, Me), 2.43 (s, 3 H, Me), 2.74 (s, 3 H, Me), 3.67 (s, 1
H, NH), 5.91 (t, 1 H, 3 J HH = 7.6 Hz, Ar), 6.10 (“dt”, 1H, 3 J HH = 7.2
Hz, 4 J HH = 0.8 Hz, Ar), 6.26 (t, 1 H, 3 J HH = 7.6 Hz), 6.28 (d, 1 H, 3 J HH
= 7.6 Hz), 6.43 (m, 3 H), 6.65 (d, 1 H, 3 J HH = 7.6 Hz), 6.71 (d, 1 H,
3 J HH = 7.6 Hz), 6.75 (t, 1 H, 3 J HH = 7.2 Hz), 6.83 (d, 4 H, 3 J HH = 7.6
Hz), 6.93 (d, 1 H, 3 J HH = 7.2 Hz), 6.98−7.06 (m, 4 H), 7.22 (“dt”, 1
H, 3 J HH = 7.6 Hz, 4 J HH = 1.2 Hz, Ar), 7.50 (d, 1 H, 3 J HH = 8.0 Hz, Ar),
7.62 (dd, 1 H, 3 J HH = 7.6 Hz, 4 J HH = 1.2 Hz, Ar), 8.07 (s, 1 H, NH),
8.16 (dd, 1 H, 3 J HH = 1.2 Hz, 4 J HH = 1.2 Hz, Ar). 13 C{ 1 H} NMR (75.5
MHz, CDCl 3 ,25°C, TMS): δ 18.0 (Me), 18.4 (Me), 18.5 (Me), 18.9
(Me), 19.1 (Me), 19.8 (Me), 20.2 (Me) 22.0 (Me), 118.0 (CH), 118.9
(CH), 119.2 (CH), 121.4 (CH), 122.8 (CH), 123.8 (CH), 124.0
(CH), 125.0 (CH), 125.8 (C), 126.0 (C), 126.5 (CH), 126.7 (C),
126.8 (CH), 126.9 (CH), 127.1 (C), 127.2 (CH), 127.3 (CH), 127.7
(CH), 127.8 (CH), 128.0 (CH), 129.3 (CH), 129.4 (CH), 129.9
(CH), 130.5 (C), 133.8 (C), 134.1 (C), 138.8 (C), 141.5 (C), 145.0
(C), 151.8 (C), 154.4 (C), 155.1 (C), 162.0 (C), 185.5 (C), 194.9
(C), 202.9 (C). IR (Nujol, cm −1 ): ν(CN) 2163. Anal. Calcd for
C 57 H 58 N 7 O 1.5 Pd 2 : C, 63.51; H, 5.42; N, 9.10. Found: C, 63.77; H,
5.21; N, 9.14. HRMS (ESI, m/z): calcd for C 57 H 56 N 7 Pd 2 [M + H] + ,
1052.2710; found, 1052.2711.
■ RESULTS AND DISCUSSION
Synthesis. We reacted our recently reported C,N,O-pincer-
Pd(II) complex [Pd{C,N,O-C(NXy)C 6 H 4 {NC(Me)CHC-
(Me)O}-2}PPh 3 ] 5 (A; Scheme 1) with PhICl 2 in CH 2 Cl 2
with the purpose of preparing a Pd(IV) complex. 3 However,
neither a Pd(IV) species nor any reductive elimination product
resulting from its likely instability were even detected. Instead,
the reaction produced variable amounts of the amino-
(iminiumacyl) complex [Pd{C,N-C(NHXy)C 6 H 4 NH 2 -
2}Cl 2 ](1; Scheme 1) along with acetylacetone (acacH) and
Ph 3 PO, which could be easily removed. These products can be
considered the result of the reaction A +2H 2 O + PhICl 2 → 1 +
acacH + Ph 3 PO. The role of PhICl 2 seemed to be limited to the
oxidation of the PPh 3 ligand. In fact, the reaction of A with
PhICl 2 in freshly distilled and degassed CH 2 Cl 2 did not afford 1
but an unstable red mixture, probably containing some Pd(IV)
species, from which we could not isolate or identify any of the
components.
We assumed that the reaction occurred in two steps: (1) A +
2HCl + H 2 O → acacH + [PdCl 2 {C(NHXy)C 6 H 4 NH 2 -
2}PPh 3 ](2c) and (2) 2c + PhICl 2 +H 2 O → 1+2HCl +
Ph 3 PO + PhI. The required initial amount of HCl is probably
present in solution as a result of the photochemical
decomposition of the solvent (CH 2 Cl 2 , see experiment
above). Consequently, we reacted A with 2 equiv of aqueous
HCl, which, in fact, allowed us to isolate complex 2c in 88%
yield. Its room-temperature 1 H and 31 P NMR spectra showed
also the presence of 1 (∼1%) and free PPh 3 , respectively,
suggesting the existence of the equilibrium 2c ⇆ 1 + PPh 3 ,
which is slow on the NMR time scale and is strongly displaced
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
to the left. Accordingly, 2c could be obtained from equimolar
amounts of 1 and PPh 3 . In addition, 1 formed when 2c was
treated with various oxidizing agents capable of removing, by
oxidizing it, the free PPh 3 existing in the equilibrium; apart
from PhICl 2 , we have used aqueous H 2 O 2 (1.5 h, 81% yield),
t BuOOH (overnight, 80% yield), or bubbling of air (40 h, 15%
yield). When A was treated with excess aqueous HCl, its amino
group was protonated and the complex [PdCl 2 {C(NHXy)-
C 6 H 4 NH 3 -2}PPh 3 ]Cl (3) was obtained. A HCl:A ≥ 4:1 molar
ratio must be used to avoid the formation of a 2c/3 mixture.
Therefore, deprotonation of 3 with NEt 3 produced 2c. As far as
we know, there is no precedent of a process like that leading to
1 from A.
The Pd−N bond in 1 can be cleaved by reacting it with
isocyanide ligands or PPh 3 to give the complexes trans-
[PdCl 2 {C(NHXy)C 6 H 4 NH 2 }-2}L] (L = t BuNC (2a),
XyNC (2b), PPh 3 (2c)). Addition of the ligand caused
dissolution of the starting suspension but, within a few minutes,
a new suspension formed and the insoluble complexes 2a−c
were isolated by filtration. Solid 2a suffers a dehydrochlorination
process when it is heated over 70 °C to produce the
complex [PdCl{C,N-C(NXy)C 6 H 4 NH 2 -2}CN t Bu] (4). In
turn, the reaction of 2c with AgClO 4 or TlTfO caused the
removal of one of the chloro ligands, the coordination vacancy
being occupied by the free NH 2 group, resulting in the
chelating complex [PdCl{C,N-C(NXy)C 6 H 4 NH 2 -2}PPh 3 ]-
ClO 4 (5). The reaction of 1 with NEt 3 did not produce a
complex of type 2; instead, this ligand was capable of producing
the dehydrochlorination of 1 to give a mixture of the bridging
iminoacyl dinuclear complex [Pd 2 Cl 2 {μ-N,C,N’-C(NXy)-
C 6 H 4 NH 2 -2} 2 ](6a) and [NHEt 3 ]Cl, which could be separated.
Replacement of the chloro ligands in 6a by acetate to give 6b
was achieved by reacting it in two steps, with TlTfO and
NaOAc. The straightforward reaction of 6a with NaOAc did
not take place, probably because of the scarce solubility of the
latter and the poorer donor ability of the acetate with respect to
that of a chloro ligand. However, removal of the chloro ligand
as the insoluble thallium salt must produce a triflato or a
solvento complex in which the poor donor ability of any of
these ligands makes them easy to replace, in spite of the low
concentration of acetate in solution. TlCl and NaCl could be
separated from the intermediate triflato complex or from 6b,
respectively, because of the solubility of the latter in acetone,
although 6b became rather insoluble once it was precipitated by
adding Et 2 O to the concentrated solution. We prepared 6b with
the intention to react it with 2-iodobenzoic acid because we
have found this to be an appropriate way to prepare Pd(IV)
complexes. 2 However, in this case, the reaction produced an
insoluble red material that darkened within a few hours and
could not be characterized. Nevertheless, in the HRMS (ESI)
spectrum of a freshly prepared sample two peaks were
identified as [6b − 2 MeCO 2 +IC 6 H 4 CO 2 + RCO 2 +H] +
where R = Ph (calcd 1028.0103, found 1028.0996) and R = Me
(calcd 967.0023, found 967.0017), which could correspond to
intermediates in the formation of the expected dinuclear
Pd(IV) complex that would be unstable.
On the other hand, we have recently reported that, while
studying the reactivity of amino(iminoacyl) Pd(II) complexes
of type B (Scheme 2), they can afford a variety of cationic 1,2-
dihydroquinazolinium-4-yl (DHQ) Pd(II) complexes (C) upon
treatment with various carbonyl compounds and triflic acid. 6,7
We have isolated reaction intermediates of the types D and E
and shown, by means of a DFT study, that the cyclization
Scheme 2
process responsible for the formation of the heterocyclic system
in C occurs through the unprecedented hydroiminiumation of
an imine. The close similarity between the cationic complex E
and the neutral 1 prompted us to react the latter with carbonyl
compounds with the aim of preparing neutral DHQ Pd(II)
complexes, of which only two precedents are known. They
were prepared by us through a different method, which is not of
general applicability, involving the hydroiminiumation of an
alkene. 5
As planned, the reaction between 1 and a neutral ligand (1:1)
in acetone allowed the synthesis of cis-[PdCl 2 {C,N-C(
NXy)CMe 2 NHC 6 H 4 -2}L] (L = XyNC (7a), PPh 3 (7b);
Scheme 3). The homologous reactions with aldehydes
Scheme 3
Article
RCHO (1:1) or with C 6 H 3 (C 6 H 4 CHO-4) 3 -1,3,5 (3:1) led to
the complexes cis-[PdCl 2 {C,N-C(NXy)CH(R)NHC 6 H 4 -
2}PPh 3 ] (R = Me (8a), Tol (8b), CHCH 2 (8c)) and
2703
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
[{cis-PdCl 2 {C(NXy)CHNHC 6 H 4 -2}CNXy} 3 {μ 3 -
C 6 H 3 (C 6 H 4 -4) 3 -1,3,5}] (9), respectively. The synthesis of 8b
required heating at 50 °C for 24 h.
As anionic DHQ Pd(II) complexes have not been reported
so far, we attempted to prepare the first such compound by
reacting 1 with [PPN]Cl in acetone. Unfortunately, the
reaction failed to give PPN[PdCl 3 {C,N-C(NHXy)-
C 6 H 4 NH 2 -2}] and the reagents were recovered almost
quantitatively after 6 h of stirring the reaction mixture at
room temperature or after refluxing it overnight.
The reaction in acetone between the cationic complex C (R
= C(O)Me) 7 or its neutral homologue 7a with 2 equiv of
TlTfO produced, after heating in a Carius tube overnight, a
black suspension from which the corresponding 4-xylyliminium-1,4-dihydroquinoline
triflate (10a,b, respectively) could
be isolated (Scheme 4). The transformation of DHQ salts into
Scheme 4
Article
rather scarce, although they have been attributed interesting
pharmacological properties. 15
When the DHQ complex C (R = H, Scheme 4) or the
neutral 7a were reacted in two steps, (i) with AgOTf and (ii)
with PhCCH and NEt 3 , depalladation occurred in both cases
to give 2,2-dimethyl-3-xylyl-4-phenylethynyl-1,2-dihydroquinazolinium
triflate (11), which is likely to form through the
intermediacy of the complex [Pd{C(NXy)CMe 2 NHC 6 H 4 -
2}(CCPh)(CNXy) 2 ]TfO; this complex, in turn, would form
by replacement of the iodo ligand by the stronger donor
phenylethynyl ligand resulting upon deprotonation of the
alkyne by the base NEt 3 . The great transphobia between the
carbon donor ligands DHQ and alkynyl would be responsible
for the instability of this complex, which would decompose
through a reductive elimination process to produce the
observed Sonogashira-type C−C coupling product. 11 The first
step was carried out in MeCN with the purpose that it occupy
the position of the iodo or chloro ligand removed by
precipitation as AgX. After filtration, the MeCN solvent was
replaced by THF in order to avoid the competition between
the solvent and the alkynyl ligand generated in situ. The same
type of reaction took place when starting from the 2-
(amino)iminoacyl complex trans-[PdI{C(NXy)NHC 6 H 4 -2}-
(CNXy) 2 ](B in Scheme 4), giving rise to H 2 NC 6 H 4 {C(
NXy)CCPh}-2 (12), which was isolated in 82% yield. A
better yield of 12 (89%) was achieved when CuI was used
instead of AgOTf, following the Sonogashira protocol. 16 In
spite of having the 2-(amino)iminoacyl ligand, complex 2c does
not react as B with AgOTf, PhCCH, and NEt 3 . In this case,
the coordination vacancy generated upon precipitation of AgCl
was occupied by the free amino fragment to give complex 5′
(Scheme 1), which did not suffer further attack by the PhC
CH/NEt 3 system. An attempt to prepare 11 from trans-
[PdI{C(NXy)CMe 2 NHC 6 H 4 -2}(CNXy) 2 ]TfO (C, R = Me)
and AgCCPh gave a complex mixture from which we could
not isolate any pure compound.
Scheme 5
4-iminium-1,4-dihydroquinoline derivatives has no precedent in
the literature but has some similarities with their rearrangement
into 4-iminium-1,2,3,4-tetrahydroquinolines, reported by us
recently. 8 We propose a similar reaction pathway for the
formation of 10 (Scheme 5). Compounds of the type 10 are
In view of the aforementioned results, we reacted B with
K t BuO in CH 2 (CN) 2 with the aim of preparing the complex
[Pd{C(NXy)CMe 2 NHC 6 H 4 -2}{CH(CN 2 )}(CNXy) 2 ]TfO
or the product H 2 NC 6 H 4 {C(NXy)CH(CN) 2 }-2 that would
result after the C−C coupling reaction. However, the reaction
produced instead the dinuclear complex 13 (Scheme 4)
containing two dianionic chelating 2-amido(iminobenzoyl)
ligands, resulting upon deprotonation of the NH 2 fragment,
one of them acting additionally as bridging. As far as we are
aware, this is the first complex of any metal containing an o-
amido(iminobenzoyl) ligand. Furthermore, in 13 there are two
2704
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
Article
such ligands coordinating differently: one bridging and the
other terminal.
X-ray Crystal Structures. The crystal structures of the
complexes 1·2DMSO (Figure 1), 5·0.5CH 2 Cl 2·0.75Et 2 O
Figure 1. (top) Crystal structure of the complex 1·2DMSO. The
solvent is omitted for clarity. The thermal ellipsoids are displayed at
the 50% probability level. Selected bond lengths (Å) and angles (deg):
Pd−C(1) = 1.9450(15), Pd−N(1) = 2.0494(13), Pd−Cl(1) =
2.3706(4), Pd−Cl(2) = 2.2906(4), C(1)−N(2) = 1.3010(19);
C(1)−Pd−N(1) = 83.46(6), C(1)−Pd−Cl(2) = 92.84(4), N(1)−
Pd−Cl(1) = 89.73(4), Cl(1)−Pd−Cl(2) = 94.206(14). (bottom)
Double chain parallel to the b axis in 1·2DMSO formed through C−
H···Cl and N−H···O hydrogen bonds.
(Figure 2), and 7a·CHCl 3 (Figure 3) and that of the 4-
iminium-1,4-dihydroquinoline 10a (Figure 4) have been
determined by X-ray diffraction. In all the palladium complexes,
the metal atom is in a square-planar environment, slightly
distorted in 1 and 5 because of the small bite of the chelating o-
amino(iminobenzoyl) ligand (C(1)−Pd(1)−N(1) = 83.46(6)
and 81.16(11)°, respectively). The two Pd−Cl bond distances
in 1 are significantly different (Pd−Cl(1) = 2.3706(4) Å, Pd−
Cl(2) = 2.2906(4) Å) because of the greater trans influence of
C-donor with respect to N-donor ligands. As expected, the Pd−
Cl(trans to C) bond distance is shorter in the cationic complex
5 (2.3402(7) Å) than in the neutral 1. Although complexes 1
and 5 could be described as carbenes, their crystal structures do
not support such an assignment. The C(aryl)−C(sp 2 ) bond
distances (1.482(2) Å in 1·2DMSO, 1.476(4) Å in
5·0.5CH 2 Cl 2·0.75Et 2 O) are close to the standard C(aryl)−
C(sp 2 ) overall value (1.488 Å), 17 and the CN bond distances
2705
Figure 2. (top) Crystal structure of the cation in the complex
5·0.5CH 2 Cl 2·0.75Et 2 O. The thermal ellipsoids are displayed at the
50% probability level, and the solvents are omitted for clarity. Selected
bond lengths (Å) and angles (deg): Pd(1)−C(1) = 1.993(3), Pd(1)−
N(1) = 2.081(3), Pd(1)−P(1) = 2.2901(7), Pd(1)−Cl(1) =
2.3402(7); C(1)−Pd(1)−N(1) = 81.16(11), C(1)−Pd(1)−P(1) =
99.43(9), N(1)−Pd(1)−Cl(1) = 88.01(7), P(1)−Pd(1)−Cl(1) =
91.38(3). (bottom) Hydrogen bonds in 5 giving rise to a chain along
the b axis.
(1.3010(19) Å in 1 · 2DMSO, 1.294(4) Å in
5·0.5CH 2 Cl 2·0.75Et 2 O) are even shorter than the standard
C(sp 2 )N(3) value (1.316 Å), 17 which confirms they are
iminobenzoyl derivatives.
The C(21)−Pd(1) bond distance in the neutral complex 7a
(1.976(2) Å) is shorter than that in the complex [PdI(DHQ)-
(CNXy) 2 ]TfO previously reported 6,7,18 (in the range
2.013(5)−2.053(2) Å), in spite of the latter being cationic.
This observation could be related to the trans influence scale I
>Br>Cl 3,4,19 and the steric demand of the ligands cis to the
DHQ ligand. In fact, in 7a the C(21)−Pd(1) bond is somewhat
folded toward the smaller chloro ligand (C(21)−Pd(1)−Cl(2)
= 86.226°) in an attempt to avoid the bulky Xy group. The
remaining bond distances and angles in 7a are in the ranges
previously found.
A search of the Cambridge Structural Database 20 shows that
only two compounds with the 4-iminium-1,4-dihydroquinoline
core, such as 10a, have been structurally characterized by X-ray
crystallography: namely, 5-benzyl-7,9-dimethoxy-3-phenyl-5Hpyrazolo[4,3-c]quinolin-1-ium
chloride acetic acid solvate and
the alkaloid isoaaptamine, which is a cancer cell growth
inhibitor. 21 In comparison to them, the most noticeable feature
in the structure of 10a is the shortening of the C(3)−N(2)
(1.370(2) vs 1.401, 1.408 Å) and N(2)−C(9) (1.336(2) vs
1.363, 1.348 Å) bond distances and the lengthening of the
C(1)−C(2) (1.446(2) vs 1.410, 1.415 Å) and C(8)−C(9)
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
Article
Figure 3. (top) Crystal structure of the complex 7a·CHCl 3 . The
thermal ellipsoids are displayed at the 50% probability level, and the
solvent is omitted for clarity. Selected bond lengths (Å) and angles
(deg): Pd(1)−C(1) = 1.923(2), Pd(1)−C(21) = 1.976(2), Pd(1)−
Cl(2) = 2.3184(6), Pd(1)−Cl(1) = 2.3952(5); C(1)−Pd(1)−C(21) =
91.55(8), C(21)−Pd(1)−Cl(2) = 86.22(6), C(1)−Pd(1)−Cl(1) =
87.70(6), Cl(2)−Pd(1)−Cl(1) = 94.157(19). (bottom) Classical N−
H···Cl hydrogen bonds giving rise to ribbons parallel to [101].
(1.379(2) vs 1.346, 1.345 Å) distances, suggesting some
electron delocalization of the double bond over the heterocyclic
ring, which also seems to extend over the aromatic ring, in view
of the shortening of the C(4)−C(5) (1.368(2) Å) and C(6)−
C(7) (1.372(2) Å) bond distances with respect to the
remaining aromatic C−C distances, which are in the range
1.403(22)−1.413(2) Å. Neither of the two aforementioned
compounds shows similar delocalization. The three structures
coincide only in the exocyclic CN bond distance
(1.3465(19) Å in 10a vs 1.344 and 1.341 Å, respectively).
Intermolecular C−H···Cl interactions along with two
classical N−H···O hydrogen bonds between the NH 2 ligand
and one of the two DMSO, present in the structure of
1·2DMSO, arrange the molecules in double chains parallel to
the b axis (Figure 1, bottom). Additionally, other N−H···O, C−
H···O, and C−H···Cl interactions result in a complex threedimensional
packing (not shown). The structure of
5·0.5CH 2 Cl 2·0.75Et 2 O shows the molecules arranged into
dimers because of the intermolecular N−H···Cl hydrogen
bonds formed between the NH 2 group and the chloro ligand.
Additionally, the dimers are connected into ribbons along the b
axis (Figure 2, bottom) through three C−H···O and one N−
H···O interaction with participation of the perchlorate anion.
Intermolecular classical N−H···Cl hydrogen bonds in
7a·CHCl 3 give rise to ribbons of molecules parallel to [101]
(Figure 3, bottom), which arrange into a three-dimensional
packing (not shown) by nonclassical C−H···Cl interactions
from the chloroform molecules. Classical N−H···O and
Figure 4. (top) Crystal structure of complex 10a. The thermal
ellipsoids are displayed at the 50% probability level, and the hydrogen
atoms are omitted for clarity. Selected bond lengths (Å): N(1)−C(1)
= 1.3465(19), N(2)−C(9) = 1.336(2), N(2)−C(3) = 1.370(2),
C(1)−C(8) = 1.401(2), C(1)−C(2) = 1.446(2), C(2)−C(3) =
1.410(2), C(2)−C(7) = 1.413(2), C(3)−C(4) = 1.403(2), C(4)−
C(5) = 1.368(2), C(5)−C(6) = 1.405(2), C(6)−C(7) = 1.372(2),
C(8)−C(9) = 1.379(2). (bottom) Intermolecular C−H···O and N−
H···O hydrogen bonds giving rise to a chain along the c axis.
nonclassical C−H···O hydrogen bonds are observed in 10a
between the triflate anion and the cation (Figure 4, top). All of
them together give a chain along the c axis (Figure 4, bottom).
IR and NMR Spectra. The IR spectra of all the new species
were measured and, apart from the corresponding ν(NH),
ν(CC), or ν(CN) absorptions which are given in the
Experimental Section, show a variable number of bands in the
1530−1650 cm −1 region, which must correspond to pure or
combined ν(CO), ν(CN), or aromatic ν(CC) stretching
modes. We have not included these bands in the Experimental
Section because we could not assign them unequivocally. The
ν(PdCl) bands could only be assigned in some cases.
Although complex 1 is rather insoluble, its NMR spectra
could be measured in DMSO-d 6 and show the expected
resonances. Complexes 2 are also poorly soluble and their
NMR spectra are of poor quality, even at low temperature (2b).
Except for the shifting of a water resonance appearing at 3.50
and 5.24 ppm in the 1 H NMR spectra of 2c and 3, respectively,
the NMR spectra of both compounds in DMSO-d 6 are
coincident. This suggests the deprotonation of the cationic
complex by the deuterated solvent, and the formation of
[(CD 3 ) 2 SOH]Cl would explain the shifting of the water
resonance by hydrogen-bond formation. Although the IR
spectrum of 2b shows two strong ν(CN) bands at 2203 and
2180 cm −1 , suggesting the presence of two geometrical isomers,
this cannot be assessed by 1 H NMR, which even at −20 °C
shows broad resonances. However, the 13 C NMR spectrum at
the same temperature does not show duplicated resonances.
Therefore, the ν(CN) duplicity could be attributed to some
2706
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
solid effect. No signs of two isomers were found for complexes
2a and 2c.
The NMR spectra of complex 5 show the presence of two
geometric isomers, which could be assigned after measuring the
spectra of a crystalline sample of the pure SP-4-4 isomer. This
shows the NHC resonance at frequency higher than that of
the SP-4-4 isomer (11.61 vs 8.69 ppm) coupled to the PPh 3
ligand in a trans position ( 4 J HP = 10.4 Hz).
We propose that in complexes 6 it is the iminobenzoyl
fragmentand not the chloro ligandthat takes the role of
the bridging ligand on the basis of NMR data. In fact, we have
previously shown 5,22 that the Xy group is free to rotate around
the N−C bond in mononuclear xylyl(imino)benzoyl complexes,
while its rotation is restricted in bridging iminobenzoyl
derivatives, causing duplication of the Me and ortho and meta
aryl resonances. It is likely that the N−Pd coordination forces
the Xy group to fold toward the aryl group, in which H7
hinders its rotation (see Chart 1). The 1 H NMR spectra of
complexes 6 are compatible with the halves of the molecule
being equivalent and the Xy group rotation around the Xy−N
bond being slow on the NMR time scale. The NH 2 hydrogen
atoms give rise to an AB system, probably because the molecule
is not planar. In the case of 6b half of the AB system is
obscured by the aromatic resonances. The 13 C NMR of 6b
could not be measured, but we think its structure is analogous
of that of 6a in view of the close similarity of their 1 H NMR
spectra.
Because of the poor solubility of complexes 7a,b, their 1 H
NMR spectra could be measured in DMSO-d 6 , showing only
after prolonged acquisition the expected resonances. The NMR
spectra of 8 and 9 follow the same pattern as those of their
cationic homologues bearing “PdI(L) 2 ” instead of
“PdCl 2 (L)”. 6,7 We assume the chloro ligands to be in mutually
cis positions, because this is the case in the three dichloro
complexes structurally characterized (1, 5, and 7). Their spectra
can be explained by taking into account the different nature of
the two ligands cis to the iminobenzoyl group, the restricted
rotation around the C−PdCl 2 L bond, and the presence of a
chiral carbon atom in each 1,2-dihydroquinazolinium fragment.
The NMR spectra of the organic species 10−12 show the
expected resonances. Although, unfortunately, we could not get
single crystals of the dinuclear complex 13, we think the
proposed structure is the only one compatible with its NMR
and high-resolution mass spectra. The NMR spectra show
resonances for five XyNC (two of them incidentally
coincident) and two inequivalent o-phenylene moieties. The
halves of the two coincident XyNC fragments give rise to a
single set of resonances, indicating their free rotation. However,
this is not the case for the third XyNC ligand and the two
iminobenzoyl fragments, which show duplicated resonances. In
addition, while one of the NH resonances appears in the
normal region (8.07 ppm vs 7.87 (1) and 7.59−7.93 ppm (2a−
c)), the other is highly shielded, probably caused by its vicinity
to two electron-rich palladium atoms, as previously reported. 23
The molar conductivities of products 3, 4, 4’, 10a,b, and 11,
measured on approximately 5 × 10 −4 M acetone solutions (see
the Experimental Section), confirm their formulations. 24
■ CONCLUSION
In summary, we report a novel hydrolysis/phosphineabstraction
process from a pincer Pd(II) complex, which allows
the isolation of neutral and cationic mono- and dinuclear 2-
amino(iminobenzoyl) complexes, some of which have been
Article
used to prepare the first family of neutral 1,2-dihydroquinazolinium-4-yl
mono- and trinuclear Pd(II) complexes. Some
depalladation reactions allowed us to isolate 1,4-dihydroquinolines,
a 4-phenylethynyl-1,2-dihydroquinazolinium salt, and a 3-
■phenylprop-2-ynylbenzenamine.
ASSOCIATED CONTENT
*S Supporting Information
CIF files giving crystallographic data for 1·2DMSO,
5·0.5CH 2 Cl 2·0.75Et 2 O, 7a·CHCl 3 , and 10a. This material is
available
■
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: jvs1@um.es.
■ ACKNOWLEDGMENTS
We thank the Spanish Ministerio de Ciencia e Innovacioń
(grant CTQ2007-60808/BQU, with FEDER support) and
Fundacioń Seńeca (grants 02992/PI/05 and 04539/GERM/
06) for financial support.
■ DEDICATION
† Dedicated to the memory of Prof. F. Gordon A. Stone.
■ REFERENCES
(1) Munĩz, K. Angew. Chem., Int. Ed. 2009, 48, 9412. Xu, L. M.; Li, B.
J.; Yang, Z.; Shi, Z. J. Chem. Soc. Rev. 2010, 39, 712.
(2) Vicente, J.; Arcas, A.; Julia-Hernandez, F.; Bautista, D. Angew.
Chem., Int. Ed. Engl. 2011, 50, 6896.
(3) Vicente, J.; Arcas, A.; Julia-Hernandez, F.; Bautista, D. Chem.
Commun. 2010, 46, 7253.
(4) Vicente, J.; Arcas, A.; Julia-Hernandez, F.; Bautista, D. Inorg.
Chem. 2011, 50, 5339.
(5) Vicente, J.; Chicote, M. T.; Martıńez-Martínez, A. J.; Jones, P. G.;
Bautista, D. Organometallics 2008, 27, 3254.
(6) Vicente, J.; Chicote, M. T.; Martıńez-Martínez, A. J.; Bautista, D.
Organometallics 2011, 2425.
(7) Vicente, J.; Chicote, M. T.; Martıńez-Martínez, A. J.; Bautista, D.
Organometallics 2009, 28, 5915.
(8) Vicente, J.; Chicote, M. T.; Martıńez-Martínez, A. J.; Bautista, D.;
Jones, P. G. Org. Biomol. Chem. 2011, 9, 2279.
(9) Mikiciuk-Olasik, E.; Blaszczak-Swiatkiewiz, K.; Urek, E.;
Krajewska, U.; Rozalski, M.; Kruszynski, R.; Bartczak, T. J. Arch.
Pharm. Pharm. Med. Chem. 2004, 337, 239. Michael, J. P. Nat. Prod.
Rep. 2008, 25, 166. Tinker, A. C.; Beaton, H. G.; Boughton-Smith, N.;
Cook, T. R.; Cooper, S. L.; Fraser-Rae, L.; Hallam, K.; Hamley, P.;
McInally, T.; Nicholls, D. J.; Pimm, A. D.; Wallace, A. V. J. Med. Chem.
2003, 46, 913.
(10) Vicente, J.; Arcas, A.; Bautista, D.; Tiripicchio, A.; Tiripicchio-
Camellini, M. New J. Chem. 1996, 20, 345. Vicente, J.; Abad, J. A.;
Frankland, A. D.; Ramírez de Arellano, M. C. Chem. Eur. J. 1999, 5,
3066. Vicente, J.; Abad, J. A.; Loṕez-Serrano, J.; Clemente, R.; Ramírez
de Arellano, M. C.; Jones, P. G.; Bautista, D. Organometallics 2003, 22,
4248. Vicente, J.; Saura-Llamas, I.; Cuadrado, J.; Ramirez de Arellano,
M. C. Organometallics 2003, 22, 5513. Vicente, J.; Arcas, A.; Gaĺvez-
Loṕez, M. D.; Jones, P. G. Organometallics 2006, 25, 4247.
(11) Vicente, J.; Arcas, A.; Bautista, D.; Jones, P. G. Organometallics
1997, 16, 2127. Vicente, J.; Arcas, A.; Gaĺvez-Loṕez, M.-D.; Juliá-
Hernańdez, F.; Bautista, D.; Jones, P. G. Organometallics 2008, 27,
1582.
(12) Spencer, J.; Pfeffer, M.; DeCian, A.; Fischer, J. J. Org. Chem.
1995, 60, 1005. Beydoun, N.; Pfeffer, M.; DeCian, A.; Fischer, J.
Organometallics 1991, 10, 3693. Pfeffer, M.; Sutter, J.-P.; Rotteveel, M.
A.; De Cian, A.; Fischer, J. Tetrahedron 1992, 48, 2427. Maassarani, F.;
Pfeffer, P.; Le Borgne, G. J. Chem. Soc., Chem. Commun. 1987, 565.
2707
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708

Organometallics
Article
(13) Vicente, J.; Abad, J. A.; Förtsch, W.; Loṕez-Saéz, M.-J.; Jones, P.
G. Organometallics 2004, 23, 4414. Vicente, J.; Saura-Llamas, I.;
Garcıá-Loṕez, J.-A.; Calmuschi-Cula, B.; Bautista, D. Organometallics
2007, 28, 2768. Vicente, J.; Saura-Llamas, I.; Garcıá-Loṕez, J.-A.;
Bautista, D. Organometallics 2009, 28, 448.
(14) Brunel, J.; Mongin, O.; Jutand, A.; Ledoux, I.; Zyss, J.;
Blanchard-Desce, M. Chem. Mater. 2003, 15, 4139.
(15) Avetisyan, A. A.; Aleksanyan, I. L.; Ambartsumyan, L. P. Russ. J.
Org. Chem. 2008, 44, 723. Wasley, W. F.; Gruenfeld, N. Ger. Offen.
DE 1816700 C3 19730315, 1969, and S. African ZA 6807889
19690701, 1969. Manickam, M.; Prasad, K. J. R. Z. Naturforsch., B
2009, 64, 851.
(16) Chinchilla, R.; Nájera, C. Chem. Rev. 2007, 107, 874. Vicente, J.;
Chicote, M. T.; Aĺvarez-Falcoń, M. M.; Jones, P. G. Organometallics
2005, 24, 2764. Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron
Lett. 1975, 16, 4467.
(17) Allen, F. H.; Kennanrd, O.; Watson, D. G.; Brammer, L.; Orpen,
G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1.
(18) Martıńez-Martıńez, A. J.; Chicote, M. T.; Bautista, D. J. Chem.
Crystallogr. 2011, 41, 1961.
(19) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335.
(20) CCDC version 5.3, updated Aug 2011
(21) Pettit, G. R.; Hoffmann, H.; McNulty, J.; Higgs, K. C.; Murphy,
A.; Molloy, D. J.; Herald, D. L.; Williams, M. D.; Pettit, R. K.; Doubek,
D. L.; Hooper, J. N. A.; Albright, L.; Schmidt, J. M.; Chapuis, J.-C.;
Tacket, L. P. J. Nat. Prod. 2004, 67, 506.
(22) Vicente, J.; Chicote, M.-T.; Abellań-Loṕez, A.; Bautista, D.
Dalton Trans. 2011, 40; DOI:10.1039/c1dt11445j.
(23) Díez, L.; Espinet, P.; Miguel, J. A. Dalton Trans. 2001, 1189.
(24) Geary, W. J. Coord. Chem. Rev. 1971, 7, 81.
2708
dx.doi.org/10.1021/om200986k | Organometallics 2012, 31, 2697−2708