Reaction of the η2(4e)-donor alkyne complexes [Mo{η2(4e)-R1C2R2}{P(OMe)3}2(η-C5H5)](R1= R2= Ph or Me; R1= Me, R2= Ph) with the Grignard reagents MgR3(X)(R3= Me, Et, CH2Ph, CH2CHCH2 or CHCH2) and CH2(MgI)2
Abstract
Reaction of the complex [Mo{η2(4e)-PhC2Ph}{P(OMe)3}2(η-C5H5)][BF4]1 with MgR(X)(R = Me, Et or PhCH2) afforded good yields of [Mo{η2(4e)-PhC2Ph}R{P(OMe)3}(η-C5H5)]. Unexpectedly, reaction of 1 with the 1,1-di-Grignard reagent CH2(MgI)2 gave the X-ray crystallographically identified zwitterionic complex [Mo{η2(4e)-PhC2Ph}{η2-P(OMe)2OBF2OP(OMe)2}(η-C5H5)], similar reactions with the but-2-yne and 1-phenylprop-2-yne complexes affording the analogous [Mo{η2(4e)-(RC2R2){η2-P(OMe)2OBF2OP(OMe)2}(η-C5H5)](R = R2= Me; R = Me, R2= Ph). Treatment of the zwitterionic diphenylacetylene- and 1-phenylprop-2-yne-substituted complexes with K[BHBus3] gave the anionic η2(3e)-vinyl complexes K[[graphic omitted]H(Ph)}{η2-P(OMe)2OBF2OP(OMe)2(η-C5H5)](R = Ph or Me). Protonation (HBF4·Et2O) of the diphenyl-substituted η2(3e)-vinyl complex followed by addition of carbon monoxide, trimethyl phosphite, or diphenylacetylene afforded trans-stilbene and the complexes [Mo(CO)2{η2-P(OMe)2OBF2OP(OMe)2}(η2-C5H5)], [Mo{P(OMe)3}2{η2-P(OMe)2OBF2OP(OMe)2}(η-C5H5)] and [Mo{η2(4e)-PhC2Ph}{η2-P(OMe)2OBF2OP(OMe)2}(η-C5H5)] respectively. When CH2CHCH2MgBr was added to 1 an unstable compound was formed, which on addition of P(OMe)3 gave [Mo{η3-C(Ph)C(Ph)CH2CHCH2}{P(OMe)3}2(η-C5H5)], the identity of which was confirmed by X-ray crystallography. This reaction is explained in terms of an unusual metalla-3,3-sigmatropic shift process. A similar reaction between 1 and CH2CHMgBr followed by addition of P(OMe)3 surprisingly gave the η3-cyclopropenyl complex [Mo(η3-C3Ph2Me){P(OMe)3}2(η-C5H5)]. The complex [Mo{η2(4e)-PhC2Ph}Me{P(OMe)3}(η-C5H5)] reacted thermally (78 °C) with an excess of PhC2Ph to give the X-ray crystallographically identified complex [MoH(η4-C5H2Ph4){P(OMe)3}(η-C5H5)], which on heating (100 °C) afforded the dihydride [MoH2(η5-C5HPh4)(η-C5H5)].