Synthesis, structure, and oxidation-induced dimerization of a cheating bis(phosphite) Ruthenium carbonyl

The novel bis(phosphite) compound Ru(bbmb)(CO)₃ (1) {bbmb: 2,2′-bis[(1,1′-bipheny]-2,2′-diyl)phosphite]-3,3′-di-t- butyl-5,5′-di-methoxy-1,1′-biphenyl} was synthesized by the high pressure reaction of Ru₃(CO)₁₂ with bbmb, and fully characterized by combustion, spectroscopic, spectrometric and structural analysis. The structure of 1, as determined by X-ray diffraction, is a nearly perfect trigonal bipyramid with the bbmb ligand coiled about Ru in an overall C₂ fashion. Reaction of 1 with [Cp₂Fe][PF₆] gave [Ru₂(μ-bbmb)₂(CO)₆][PF₆]₂ (2) whose formulation is based on combustion and spectroscopic analysis. It is shown that 2 contains a pair of bridging bbmb ligands. The significance of 1 in relation to structure- activity in the regioselectivity of the hydroformylation reaction is discussed. Formation of 2 from 1 is addressed in the context of the reactivity of pentacoordinate radical cation complexes.