ca01 only detailed ToC 1..24

132 Science of Synthesis 2.6 Complexes of Cr, Mo, and W without CO Ligands
in vacuo). The synthesis of 84 proceeds via the protonolysis of the tungsten-methyl bond
with aniline to form an arylamide ligand (Scheme 38), [152] and Scheme 45 illustrates related
examples involving benzoic acid and ammonium chloride (98 and 99, respectively).
[174,175] Hydrocarbyl groups other than ó-alkyls may also be used as precursors for this
reaction, as demonstrated by the reaction of chromocene with tert-butyl alcohol to give
100. [176]
Scheme 45 Syntheses from ó-Alkyl Complexes [174–176]
W(Me)2(Cp) 2
W(Me) 2(Cp) 2
Cr(Cp) 2 + Bu t OH
+ PhCO2H
+ NH 4Cl
petroleum ether
60 oC 90%
THF, 56 oC 61%
toluene, 110 oC 84%
WMe(Cp) 2Cl
99
{CrCp(OBut )} 2
100
WMe(Cp)2(O2CPh)
(Benzoato-O)bis(ç 5 -cyclopentadienyl)methyltungsten(IV) (98); Typical Procedure: [174]
The compound [W(Me) 2(Cp) 2] (0.52 g, 1.52 mmol) in petroleum ether (bp 100–1208C,
25 mL) was treated with benzoic acid (0.19 g, 1.51 mmol) and the mixture was warmed to
608C. Methane was evolved and the soln turned red. After 1 h the soln was filtered and
slowly concentrated under reduced pressure. Red-brown crystals separated which were
collected by filtration, washed with petroleum ether (2 ” 15 mL), and finally recrystallized
(petroleum ether/Et 2O 2:1); yield: 0.61 g (90%).
2.6.8.4 Method 4:
FromCarbene or Carbyne Complexes
Addition of the conjugate acid of the desired ligand to a metal–carbene or –carbyne compound
results in protonation of the hydrocarbyl ligand (see also Sections 2.6.1.4 and
2.6.4.4), transforming it into an alkyl or carbene ligand with formation of a new metalheteroatom
bond. Examples are the preparations of compound 19 (Scheme 7) and compound
65 (Scheme 27). The reaction of the carbene substrate 101 with tert-butyl alcohol
produces product 102 (Scheme 46) which, upon heating, eliminates alkane and affords a
new carbene compound in an overall process which resembles the protonolysis of an alkyl
complex (Section 2.6.8.3). [19] The same reaction of 101 with triphenylsilanol at low
temperatures leads to the protonolysis product directly.
Scheme 46 Synthesis from a Carbene Complex [19]
NMe2
CH2TMS
W
CHTMS
N
Ph
101
+ ButOH pentane
NMe2
CH2TMS
W CH2TMS
98
Bu N
Ph
tO 102