STRUCTURE AND CONFORMATION OF METAL CLUSTER COMPLEXES FROM TRIPHENYLPHOSPHINE RUTHENIUM CARBONYL CARBOXYLATES. S. Ianelli & M. Nardelli, Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universita' di Parma, Viale delle Scienze 78, I-43100 Parma, Italy. M.Bianchi, P.Frediani, A.Salvini, C.Faggi, S. Papaleo, F. Piacenti, Dipartimento di Chimica Organica "Ugo Schiff", Universita' di Firenze, Via G. Capponi 9, I-50121 Firenze, Italy.

The behaviour of Ru(CO)2(MeCO2)2(PPh3)2 (1), Ru2(CO)4(MeCO2)2(PPh3)2 (4) and Ru4(mu-H)4(CO)8(PPh3)4 (9) with H2 under 100 atm pressure at different temperatures has been studied and the obtained products characterized. The molecular structures of Ru3(mu-H)2(CO)8(mu3-PPh) (PPh3) (5), Ru4(CO)8(mu4-PPh)2(mu-PPh2)2 (7) and Ru4(mu-H)4(CO)7(mu4-PPh) (mu-PPh2)2 (PPh3) (8), obtained from compound (4), have been determined in the solid state by single crystal X-ray diffraction. The hydride nature of compounds (5) and (8) has been shown both from the N.M.R. spectra and X-ray analysis, while no hydride hydrogen was found in compound (7). The knowledge of the structures allows to interpretate the formation reactions of the compounds obtained. The conformation of the phosphine ligands is considered in connection with the intramolecular steric hindrance and packing requirements.