TRANSITION-METAL CARBYNE COMPLEXES .100. SYNTHESIS OF ELECTRON RICH DIETHYLAMINOCARBYNE COMPLEXES OF TUNGSTEN FROM CP(BR)2(CO)WCNET2

Oxidative decarbonylation of Cp(CO)2W = CNEt2 (Cp = eta-5-C5H5) (1) with Br2 to give Cp(Br)2(CO)W = CNEt2 (2) followed by reductive elimination of the bromide ligands in 2 by Na/Hg in the presence of a 2e-donor ligand L represents a convenient route to electron-rich diethylaminocarbyne complexes of the type Cp(CO)(L)W = CNEt2. This is demonstrated by the synthesis of the isocyanide and phosphane complexes Cp(CO)(RNC)W = CNEt2 (3a, 3b) (a: R = Et; b: R = t(Bu) and Cp(CO)(PR3)W = CNEt2 (3a, 3d) (c: R = Me; d: R = Ph).