ca01 only detailed ToC 1..24

96 Science of Synthesis 2.6 Complexes of Cr, Mo, and W without CO Ligands
Scheme 6 Carbene Transfer [31–33]
R 1
R 1
N
R 1 = H, Me, iPr
Cl
L
L W L
Cl L
15
L = PMe 2Ph
E = O, N-4-Tol
R1 ,R2 = (CH2) 4, Me2 E
W
ButO OBut OBut ButO E = O, NPh
Cl
W
Cl
OCMe(CF3) 2
OCMe(CF3) 2
E
R1 , benzene
2 R
45−88%
Na/Hg,
TaCl3( CHBut )(PMe3)2
Et2O, rt, 12 h
79−83%
OMe
benzene, THF, rt, 8 h
71%
E
Cl W CR
Cl
1R2 L
L
16
PPh3
PMe3 Cl E
W
Cl CHBu
PMe3 17
t
MeO
(F3C) 2MeCO
THF W
OCMe(CF
N
3)2
R 1 R 1
(2,6-Dimethylphenylimido)bis(1,1,1,3,3,3-hexafluoro-2-methylpropan-2-olato)(2-methoxybenzylidene-kC)(tetrahydrofuran)tungsten(VI)
(14,R 1 = Me); Typical Procedure: [31]
The compounds [WCl 2{OCMe(CF 3) 2} 2(=NC 6H 3-2,6-Me 2)(THF)] (16.0 g, 19.8 mmol) and
Ph 3P=CH(C 6H 4-2-OMe) (7.78 g, 20.3 mmol) were dissolved in a mixture of benzene and
THF (160 mLand 2.5 mL, respectively) and the resulting soln was added to 1% Na/Hg
(3.59 g of Na, 7.90 equiv). After being stirred for 8 h at rt, the mixture was allowed to settle,
and the orange-brown supernatant was added via a cannula to CuCl (2.07 g, 20.9 mmol).
The residual Na/Hg was washed with Et 2O (120 mL), and the combined benzene/Et 2O soln
was stirred with CuCl for 12 h before removal of the solvent in vacuo. The brown solid
was then extracted with Et 2O (260 mL). After addition of THF (2 mL) to the extract and filtering,
the soln was slowly cooled to –508C to yield the product as an olive-yellow powder;
yield: 12.0 g (71%); 1 H NMR (benzene-d 6, ä): 10.81 (s, W=CHAr).
2.6.1.4 Method 4:
FromCarbyne Complexes
Addition of a proton to a carbyne ligand may transform it into a carbene. The proton can
be provided by an external source or by transfer from another ligand. Examples of the
first kind are provided by the addition of acids to complex 18 (see Scheme 7). [7] The use
of pyridinium salts yields more stable pyridine adducts. This reaction can be reversed by
the addition of a strong base (see Section 2.6.2). When an acid containing a noncoordinating
anion is used, e.g. trifluoromethanesulfonic acid, cationic derivatives may be obtained.
[34] Depending on the nature of the coligands, the proton may preferentially add
to another position in the molecule (see Section 2.6.2).
Internal proton transfer is observed for amido ligands. The reaction between the 1,2dimethoxyethane
adduct of trichloro(carbyne)molybdenum or -tungsten complexes and
(trimethylsilyl)arylamines produces the stable intermediates 20. The latter, however, re-
14