A study of acetylene and acetylide carbonyl and diphosphine substituted ruthenium trinuclear clusters: synthesis and structural characterization.

The synthesis and structural characterization of the acetylene and acetylide carbonyl ruthenium clusters: [Ru3(CO)9(?-CO){?3-?2-(//)-HCCR}] [R = C6H4-4-CH3 (1a), C6H3-2,5-(CH3)2 (1b), C6H2-2,4,5-(CH3)3 (1c), C6H4-4-tBu (1d), C6H4-4-COH (1e), C6H4-4-NH2 (1f)] and [Ru3(CO)9(?-H){?3-?2-(?)-CCR}] [R = C6H4-4-CH3 (2a), C6H3-2,5-(CH3)2 (2b), C6H2-2,4,5-(CH3)3 (2c), C6H4-4-tBu (2d), C6H4-4-COH (2e), C6H4-4-NH2 (2f)] are described. Compounds 1a?f were obtained under very mild conditions from the known [Ru3(CO)10(NCMe)2] activated cluster in the presence of the monosubstituted phenylacetylenes; in all cases, the alkynes are coordinated to the metallic fragment as acetylene groups in a ?3-?2 parallel fashion without breaking the C(sp)?H bond of the triple bond. In solution compounds of the 1 series slowly transformed to the acetylide derivatives (2), where the acetylene group undergoes an oxidative addition and a rearrangement of the ?CC? coordinated fragment to a ?3-?2 perpendicular coordination mode of the C?C axis by breaking the C(sp)?H bond to give a hydride ligand in each case. The diphosphines substituted derivatives [Ru3(CO)7(?-diphosphine)(?-H){?3-?2-(?)-CCR}] [diphosphine = dppe; R = C6H4-4-CH3 (3a), C6H3-2,5-(CH3)2 (3b), C6H2-2,4,5-(CH3)3 (3c) and diphosphine = dfppe; R = C6H4-4-CH3 (4a), C6H3-2,5-(CH3)2 (4b), C6H2-2,4,5-(CH3)3 (4c)] were obtained from the reaction of the [Ru3(CO)10(diphosphine)] cluster (diphosphine = dppe or dfppe) with the terminal alkyne, respectively. All compounds have been characterized in solution by infrared spectroscopy and multinuclear magnetic resonance. The solid state structures of the acetylide compounds 2b?d and 3b have been established by single crystal X-ray diffraction studies; the ?CC? fragment was observed in a ?3-?2 perpendicular coordination mode.