Kinetic and structural studies of the reactions of phosphorous nucleophiles with the sulfido bimetallic clusters Cp'2Mo2Co2S3(CO)4 and Cp'2Mo2Co2S4(CO)2. X-ray crystal structure of Cp'2Mo2Co2S3(CO)4(PMe3)

Abstract

The syntheses of the carbonyl substituted clusters Cp' 2 Mo 2 Co 2 S 3 (CO) 4-n L n , n=1, 2, Cp'=η 5 -C 5 H 4 Me, L=PPh 3 , P(n-Bu) 3 , P(OMe) 3 , PPh 1 H, and PPhH 2 , are described. Kinetic studies were performed that show the CO substitution involves two elementary steps; an adduct is forms in a preequilibrium step, followrd by CO dissociation from the adducts. equilibrium constants and CO-dissociation rate constants were obtained. The formation of the initial adduct is associative. Typical activation parameters are ΔH = 24±3 kcal/mol, ΔS = 0±8 eu for CO dissociation and ΔH = 6 kcal/mol, ΔS = -28 eu for associative adduct formation with PPh 3