ETA(1)-ARYL-BRIDGED TRIRUTHENIUM CLUSTER COMPLEXES

Both triphenylphosphine ligands of the cluster complex [Ru3(mu-H)(mu3- ampy)(PPh3)2(CO)7] (ampy = 2-amino-6-methylpyridinate; 1a) undergo a c arbon-phosphorus bond scission on reaction with hydrogen (toluene, 110 -degrees-C, 1 atm) to give the eta1-phenyl-bridged derivative [Ru3(mu- Ph)-(mu3-ampy)(mu-PPh2)2(CO)6] (2a). The compound 2a.CH2Cl2 has been c haracterized by X-ray crystallography. An extended Huckel molecular or bital calculation describing the interaction of the bridging phenyl gr oup with the trimetallic fragment is also reported. The new complexes [Ru3(mu-H)(mu3-ampy)(ER3)2(CO)7] (ER3 = PMe2Ph (1b), PCY3 (1c), P(P-to lyl)3 (1d), AsPh3 (1e)) have been prepared in order to compare their b ehavior toward hydrogen with that of complex 1a; only 1d and 1e gave p roducts analogous to 2a, whereas 1b and 1c (unlike the others, 1c is n ot isostructural with 1a) gave mixtures of unidentified products. Anot her eta1-phenyl-bridged compound, namely, [Ru3(mu-Ph)(mu3-mbim)(mu-PPh 2)2(CO)6] (mbim = 2-mercaptobenzimidazolate) has been obtained, withou t the use of hydrogen, from the reaction of [Ru3(mu-H)(mu3-mbim)(CO)9] with PPh3 in refluxing THF.