REACTIONS OF ORGANIC ISOCYANIDES WITH THE MIXED-METAL CLUSTERS CP'2MO2CO2S3(CO)4 AND CP'2MO2CO2S4(CO)2

The bimetallic cluster Cp'2Mo2Co2S3(CO)4 reacts with tert-butyl or met hyl isocyanide to give sequentially the mono-, di-, and trisubstituted clusters CP'2Mo2Co2S3(CO)4-x(L)x. The disubstituted derivatives are f ormed as a mixture of cis and trans isomers that are readily distingui shed by their AMR spectra. Color changes and NMR evidence indicate tha t the adducts CP'2Mo2Co2S3(CO)4-x+1(L)x are formed prior to the loss o f CO in the substitution reactions; the reluctance of the adduct with x = 4 to lose CO is invoked to explain the lack of formation of tetras ubstituted derivatives.