THE CLUSTER ANION [HRU3(CO)8(MU-PPH2)2]- AS A BUILDING BLOCK FOR THE ASSEMBLY OF BIMETALLIC TETRANUCLEAR CLUSTERS - SYNTHESIS, STRUCTURE, FLUXIONALITY, AND REACTIVITY - SYNTHESES AND STRUCTURES OF [H2RU3RH(MU-CO)(CO)6(PPH3)2(MU-PPH2)(PPHC6H4)] AND [H2RU3IR(MU-CO)(CO)7(PPH3)(MU-PPH2)(PPHC6H4)]

The anionic cluster [HRu3(CO)8(μ-PPh2)2]- (1) is obtained from the reaction of [HRu3(CO)11]- with PPh2H in THF solution. The solid-state structure of 1 has been determined by a single-crystal X-ray analysis of the bis(triphenylphosphine)iminium salt. Crystals are triclinic, space group P1, with Z = 2 in a unit cell of dimensions a = 14.690 (6), b = 18.652 (4), c = 12.150 (2) Å, α = 106.60 (2), β = 92.17 (2), γ = 95.89 (2)°. The structure of 1 shows a triangular metal framework of three ruthenium atoms bound to eight terminal carbonyl groups, with the two µ-phosphido ligands bridging two adjacent Ru–Ru bonds one of which is also bridged by the hydride ligand. In solution the hydride ligand was found to be fluxional by migrating from a phosphido-bridged Ru–Ru bond to the other one as documented by the temperature-dependent 31P and 1H NMR spectra. The cluster anion 1 reacts with chloro complexes to give neutral mixed-metal tetranuclear clusters. The reaction of 1 with Wilkinson’s catalyst, (PPh3)3RhCl, leads to the formation of [H2Ru3Rh(μ-CO)(CO)6(PPh3)2(μ-PPh2)(PPhC6H4)] (2), and with Vaska’s complex, (PPh3)2Ir(CO)Cl, the cluster [H2Ru3Ir(μ-CO)(CO)7(PPh3)(μ-PPh2)(PPhC6H4)] (3) is obtained. In spite of the formal analogy of 2 and 3 the structures of the two tetranuclear mixed-metal clusters, determined by X-ray diffraction methods, are entirely different. Crystals of 2 are triclinic, space group P1, with Z = 2 in a unit cell of dimensions a = 12.074 (4), b = 22.972 (8), c = 11.506 (5) Å, α = 78.55 (1), β = 101.43 (1), γ = 101.20 (1)°. Crystals of 3 are monoclinic, space group P21/a, with Z = 4 in a unit cell of dimensions a = 19.446 (4), b = 18.168 (8), c = 14.083 (6) Å, ß = 102.29 (1)°. The Ru3Rh core in 2 is in a butterfly arrangement with an orthometalated PPhC6H4 moiety bridging the Ru–Ru hinge edge and η3 interacting with the Rh atom. The Ru3Ir core in 3 is in a tetrahedral arrangement in which the PPhC6H4 ligand bridges only a tetrahedral Ir–Ru edge. © 1990, American Chemical Society. All rights reserved.