REACTIONS OF THE ISOMERS METHOXYALLENE AND METHYL PROPARGYL ETHER WITH TRIOSMIUM AND TRIRUTHENIUM CLUSTERS - CRYSTAL-STRUCTURE OF THE METHOXYALLENE CLUSTER [OS3(CO)11(MU,ETA-1,ETA-3-CH2CCHOME)]

The clusters [Os3(CO)11(CH3CN)] and [Ru3(CO)10(CH3CN)2] react with methoxyallene (CH2 = C = CHOMe) to give two isomers of [Os3(CO)11(mu-C3H3OMe)] (1a and 1b) and the dinuclear compounds [M2(CO)7(mu-C3H3OMe)] (2a, M = Os, and 2b, M = Ru). The X-ray crystal structure of cluster 1a shows it to contain a four-electron donating allene bridge which is sigma-bonded through the central carbon atom to one Os atom and eta-3-bonded to another. There is no Os-Os bond associated with this bridge and there are only two Os-Os bonds as expected. The MeO group is syn in 1a and we believe that it is anti in 1b. The clusters [Os3H2(CO)10], [Os3(CO)10(CH3CN)2] and [Ru3(CO)10(CH3CN)2] react with the isomeric methyl propargyl ether (CH = CCH2OMe) to afford the compounds [M3(CO)9(mu-CO)(mu-3-eta-2-alkyne)] (3a, M = Os, and 3b, M = Ru), [M3H(mu-3,eta-2-C = CCH2OMe)(CO)9] (4a, M = Os, and 4b, M = Ru), [Os3(CO)9(RCCHOCH = CR)], 5 and [Os3(CO)9{(RC2H)2CO}] (6, R = CH2OMe), where the last two are alkyne-coupled products.