Abstract
Protonation of alkylidyne tungsten complexes of the types [W(CR)Cl(CO)(PMe 3) 3] or [W(CR)Cl(CO)(py)(PMe 3) 2] with HCl affords the η 2-alkylidene tungsten complexes [W(CHR)Cl 2(CO)(PMe 3) 2] ( 7) (R = Me, Et, Ph, p-Tol). Protonation of the complexes [W(CR)X(CO)(CNR′)(PMe 3) 2] with HOSO 2CF 3 or HBF 4 gives the alkylidene complexes [W(CHR)X(CO)(CNR′)(PMe 3) 2][Y] ( 8) (R = Me, R′ = CMe 3, X = Cl, Y = CF 3SO 3, R = Ph, X = Cl; R′ = CMe 3, Y = CF 3SO 3, BF 4; R′ = C 6H 11, Y = BF 4; R′ = C 6H 3Me 2-2,6, Y = CF 3SO 3, R = Ph, R′ = CMe 3, X = I, Y = CF 3SO 3, BF 4). The CH bonds of the alkylidene ligands are easily deprotonated with bases such as pyrrolidinocyclopentene or triethylamine. The solid state structures of [W(CPh)Cl(CO)(CNCMe 3)(PMe 3) 2] ( 5b), [W(CHMe)Cl 2(CO)(PMe 3) 2] ( 7a). [W(CHPh)Cl 2(CO)(PMe 3) 2] ( 7c), and [W(CHPh)Cl(CO)(CNCMe 3)(PMe 3) 2][BF 4] ( 8c) were determined by X-ray crystallography. The structure of 7a was also determined by neutron diffraction. Based on the neutron diffraction data of 7a, and closely matching results from the X-ray diffraction studies, it is found that the η 2-coordination mode of the alkylidene ligands gives rise to almost equal WC(R) and WH bond distances, 1.857(4) and 1.922(6) Å, respectively, in the case of 7a. The length of the alkylidene CH bond in 7a is 1.185(7) Å. The structural comparison of 5b and 8c reveals that the protonation of the alkylidyne ligand causes the WCPh bond to lengthen by less than 0.1 Å and the WCPh angle to bend by about 15°. The major induced structural change, however, may be described as a lateral shift of the CPh group by about 0.6 Å away from the coordination axis defined by the extension of the ClW vector.
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