REACTIONS OF (PROPARGYL)DICOBALT HEXACARBONYL CATIONS WITH METHYLMETALS

Article abstract of DOI:10.1016/S0022-328X(00)85531-X

The reactions of several methyl-metallic compounds, (CH3)MLn with the cobalt complexes <(HC<*>CCR¹R²)Co2(CO)6>⁺BF4^- (I) and (HC<*>CCR¹R²OAc)Co2(CO)6 (VIII) have been examined and assessed as a synthetic method for methyl/propargyl coupling.No methyl transfer was observed in the reactions of the cationic complexes I with CH3MgI, (CH3)2Cd, (CH3)2Gg, (CH3)4Si, (CH3)4Sn or (CH3)3SiSi(CH3)3 but rather reductively coupled products, (HC<*>CCR¹R²-Cr¹R²C<*>CH)2 (III), and (HC<*>CCHR¹R²)Co2(CO)6 (V) were obtained in low yields.Modest yields (5-30percent) of methylation products (HC<*>CCR¹R²CH3)Co2(CO)6 (II) were produced from I and (C5H5)Fe(CO)2CH3 or (CH3)3Al, accompanied by varying amounts of III.The most efficient route to the methylated derivatives II (25-90percent yields) combines the complexed propargyl acetates VIII with (CH3)3Al under unusually mild conditions (CH2Cl2, -78 deg C).