NEW TRINUCLEAR AND HEXANUCLEAR RUTHENIUM CLUSTERS DERIVED FROM THE REACTION OF [RU3(CO)12] WITH PHENYLPHOSPHINE OR CYCLOHEXYLPHOSPHINE

The reaction of [Ru3(CO)12] with PPH2 (R = phenyl or cyclohexyl) has been re-examined and the involvement of the trinuclear clusters [RU3(mu-H)(mu-PHR)(CO)10], [RU3H2(mu-3-PR)(CO)9], [RU3H2(mu-3-PR)(CO)8(PH2R)] and [Ru3H2(mu-PHR)2(CO)8] in the formation of the bis-capped compound [RU3(mu-3-PR)2(CO)9] has been explored. The single-crystal X-ray structures of [RU3(mu-H)2(mu-3-PPh)(CO)8(PH2Ph)] and [RU3(mu-H)(mu-PHPh)3(CO)7] are presented. Tle latter compound was obtained as a single isomer whereas there are four isomers present in solutions of the PHCy analogue (Cy = cyclohexyl). In an unsuccessful attempt to hydrogenate [RU3(mu-3-PR)2(CO)9] to reform one of the isomers, [RU3H2(mu-PHR)2(CO)8] or [RU3H2(mu-3-PR)(CO)8(PH2R)], we obtained instead a mixture of the known compound [RU6(mu-3-PR)2(mu-4-PR)2(CO)12] and the hydrogenated form of this, [Ru6H2(mu-3-PR)2(mu-4-PR)2(CO)12]. The structures of these hexanuclear clusters are related, both being based on distorted trigonal prismatic Ru6 arrangements, but the distortions are very different and the average Ru-Ru distances in the 90-valence electron dihydride are longer than in the 88-valence electron non-hydride compound. We have identified a restricted rotation about the P-Ph bonds for the mu-4-ligands but not the mu-3-ligands which is interpreted in terms of clashes of the ortho-phenyl hydrogen atoms with CO ligands.