Synthesis and catalytic properties of heterobimetallic complexes of the tripod ligand HC(PPh2)3. X-ray molecular structures of [Rh(COD){HC(PPh2)3}Au(PPh3)](BF 4)2 and [RhCu2{HC(PPh2)3}2(THF) 2(CH3CN)2](BF4)2(F)

Article abstract of DOI:10.1021/om00056a031

Treatment of [M(COD){HC(PPh₂)₃}]BF₄ (M = Rh, Ir; 1a, 1b) with 1 equiv of the complex [Au-(PPh₃)(THF)]BF₄ in THF/CH₂Cl₂ at room temperature afforded the binuclear species [M(COD){HC-(PPh₂)₃}Au(PPh₃)](BF ₄)₂ (M = Rh, Ir; 2a, 2b). The molecular structure of 2a showed both rhodium and gold bound to a single tripod ligand in a clamped arrangement with a rhodium to gold separation of 5.431 (1) ?. The reactions of molecular hydrogen and carbon monoxide with these complexes have been studied. When the mononuclear species [Rh(COD){HC(PPh₂)₃}]BF₄ (1a) was treated with [Cu(CH₃CN)₄]BF₄ in acetonitrile, the heterobinuclear complex [Rh(CH₃CN)₃Cu{HC(PPh₂)₃}](BF ₄)₂ (6) was obtained. 6 transforms in CH₂Cl₂/THF to give the trinuclear species [RhCu₂{HC(PPh₂)₃}₂(THF) ₂(CH₃CN)₂](BF₄)₂(F) (7) for which an X-ray molecular structure was also determined. In the structure the rhodium lies on a center of symmetry, the two copper(I) ions each being 5.353 (4) ? distant from rhodium. The tetracoordinate planar arrangement of four phosphorus atoms about the rhodium results from the coordination of two tripod ligands, each providing two donor sites, leaving one phosphorus atom on each tripod to bind each Cu(I), which possesses a trigonal-planar coordination geometry. The catalytic properties of these new complexes for the hydrogenation of olefins have been briefly compared in order to probe the effect of the presence of the coinage metal on such processes. 2a·2H₂O·Et₂O crystallizes in the monoclinic space group P2₁/n (No. 14), a = 20.704 (5) ?, b = 13.686 (3) ?, c = 23.573 (5) ?, β = 109.42 (2)°, and Z = 4. The structure was refined to R = 6.4 and R_w = 10.7%, using 6924 reflections. 7·2C₆H₆ crystallizes in the triclinic space group P1 (No. 2), a = 13.544 (3) ?, b = 14.741 (3) ?, c = 13.156 (3) ?, α = 101.69 (2)°, β = 98.29 (2)°, γ = 62.76 (2)°, and Z = 1. The structure was refined to R = 10.1 and R_w = 13.6%, using 4437 reflections.