Phosphorus–sulfur bond cleavage at a mixed-metal centre; reaction of [(OC)3Co(µ-PHCCH)Mo(CO)2(η5-C5H5)] with PPh2(SPh)

Abstract

The bimetallic cobalt–molybdenum complex [(OC)4CoMo(CO)3(η5-C5H5)] reacted with phenylacetylene in benzene to give the bimetallic alkyne-bridged complex [(OC)3Co(µ-PhCCH)Mo(CO)2(η5-C5H5)]1 as the major product and the trimetallic alkylidyne-capped complex [Co2Mo(µ3-CCH2Ph)(CO)8(η5-C5H5)]2 as the minor product. Reaction of 1 with PPh2(SPh) resulted in substitution of a carbonyl group on the cobalt atom to give [{(PhS)Ph2P}(OC)2Co(µ-PhCCH)Mo(CO)2(η5-C5H5)]3. Thermolysis of 3 in refluxing toluene afforded, as the major product, the complex [η5-C5H5)(OC)Mo(µ-PPh2CHCPh)(µ-SPh)Co(CO)2]4, in which the unsymmetrical alkyne in 3 has been incorporated into a four- membered metallacycle, [graphic omitted]Ph, such that the phenyl substituent is positioned on the carbon atom remote from the phosphide group. The related complex [(η5-C5H5)(OC)Mo(µ-PPh2CHCPh)(µ-SPh)Co(CO)(PPh3)]5, in which one of the carbonyl groups on the cobalt atom in 4 has been substituted by a triphenylphosphine ligand, has also been isolated as a minor product from this reaction. Conversion of 4 into 5 has been achieved separately by reaction of 4 with PPh3. Similarly, reaction of PPh2(SPh) with 4 yields a related compound [(η5-C5H5)(OC)Mo(µ-PPh2CHCPh)(µ-SPh)Co(CO){PPh2(SPh)}]6, in which the same carbonyl group on the cobalt atom has been substituted by PPh2(SPh). Single-crystal X-ray diffraction studies have been performed on complexes 2,4 and 6.