Reactions of [Os₅(CO)₁₅C] with diphosphines; synthesis, reactivity, and the X-ray crystal structure of [Os₅(CO)₁₅C{Ph₂P(CH₂) ₂PPh₂}]

The reaction of [Os₅(CO)₁₅C] with 1,2-bis(diphenylphosphino)ethane (dppe) in CH₂Cl₂ under reflux affords the addition product [Os₅(CO)₁₅C(dppe)] (1). An X-ray crystal structure shows that the Os₅ square-pyramidal geometry of the parent carbide has opened up to give a 'wingtip-bridged butterfly' arrangement with the carbido-carbon atom lying at the centre of the metal framework. The diphosphine ligand co-ordinates in a unidentate fashion to the Os atom bridging the 'wingtips' of the 'butterfly' leaving the second phosphorus atom pendant. Reaction of complex (1) with further [Os₅(CO)₁₅C] gives a complex which has been tentatively assigned as the adduct [{Os₅(CO)₁₅C}₂(dppe)] (2).