CARBON-HYDROGEN BOND ACTIVATION BY TRIRUTHENIUM CARBONYL SPECIES DURING CARBON-MONOXIDE PROMOTED ELIMINATION OF 4,5-DIHYDROACENAPHTHYLENE FROM [(MU(2)ETA(1)ETA(5)-C12H10)RU3H2(CO)(7)] - IMPLICATION OF REACTIONINTERMEDIATES

Oxidative addition of a vinylic C-H bond occurred during the CO-promot ed elimination of 4,5-dihydroacenaphthylene (3) from [(mu(2):eta(1):et a(5)-C12H10)Ru3H2(CO)(7)] (2) in CH2Cl2. The product, [(mu(3):eta(1):e ta(2):eta(2)-C12H9)Ru3H(CO)(9)] (4), was isolated and characterized by spectroscopy and crystallography. The carbonylation of a deuterium-la belled complex, [(mu(2):eta(1):eta(5)-C12H8D2)Ru3D2(CO)(7)] (2-d(4)), under the same conditions as that from 2 to 3 in CH2Cl2 afforded 4,5-d ideuterioacenaphthylene (3-d(2)) and [(mu(3):eta(1):eta(2):eta(2)-C12H 7D2)Ru3H(CO)(9)] (4-d(2)). The lack of incorporation of deuterium atom s into the ruthenium hydride in 4-d(2) suggested that dissociation of D-2 from the triruthenium moiety in 2-d(4) induced the oxidative addit ion of the vinylic C-H bond. Further carbonylation of 4 did not occur under the same conditions as the reaction from 2 to 4, but gave 3 in m oderate yields under higher CO pressure (8 atm) at 50-100 degrees C. T hese results suggest that 4 was not directly involved in the CO promot ed elimination of 3 from 2, but was closely related to the actual inte rmediates. Possible reaction mechanisms are discussed.