Synthesis of mixed-metal clusters by the reaction of the unsaturated cluster [Os3(µ-H)2(CO)10] with transition-metal hydrides: the X-ray crystal structures of [Os3H3(CO)10{Cu(PPh3)}] and [Os3H3(CO)11{Ir(PPh3)}]

Abstract

The co-ordinatively unsaturated dihydride cluster [Os₃(µ-H)₂(CO)₁₀] reacts with the transition-metal hydrides [{CuH(PPh₃)}₆], [IrH(CO)₂(PPh₃)₂], [RhH(CO)(PPh₃)₂], and [NiH(Cl)({P(C₆H₁₁)₃}₂] to give the mixed-metal clusters [Os₃H₃(CO)₁₀{Cu(PPh₃)}](1), [Os₃H₃(CO)₁₁{Ir(PPh₃)}](2), [Os₃H₃(CO)₁₁{Rh(PPh₃)}](3), and [Os₃H₂(CO)₁₀{Ni[P(C₆H₁₁)₃]}](4). These complexes have been characterized by i.r. and n.m.r. spectroscopy, and the structures of (1) and (2) have been established by single-crystal X-ray analysis. In complex (1) the three Os atoms lie at the vertices of an isosceles triangle the long edge [3.026(3)Å] of which is bridged by the Cu atom of the Cu(PPh₃) ligand. The hydrides were not located directly but evidence suggests that they bridge the long Os–Os bond and the two Os–Cu bonds. The carbonyl arrangement is similar to that observed in [Os₃H₂(CO)₁₀]. In complex (2) the Ir atom caps the Os₃ triangle to form a distorted tetrahedral metal framework. The three Ir–Os bond lengths [2.759(3), 2.789(2), and 2.917(3)Å] show considerable variation. The distribution of the eleven terminal carbonyl ligands and the phosphine group, which is co-ordinated to the Ir atom, indicates that the three hydrides bridge the two longer Os–Os bonds, and the longest Os–Ir bond. From the spectroscopic data the overall geometry of complex (3) is closely related to that of (2), while (4) has a tetrahedral metal arrangement with hydrides and carbonyl groups bridging Os–Os and Os–Ni edges.