Role of the reversible opening of a metal-metal bond in a cluster-assisted transformation of bis(diphenylphosphino)methane

Article abstract of DOI:10.1021/om00097a015

A reinvestigation of the reaction of Ru₃(CO)₉(μ₃-η³-P(C ₆H₅)CH₂P(C₆H₅)(C ₆H₄)) (2) with carbon monoxide (Lugan, N.; Bonnet, J.-J.; Ibers, J. A. J. Am. Chem. Soc. 1985, 107, 4484-4491) under milder conditions shows that at room temperature 2 is in equilibrium with the adduct Ru₃(CO)₁₀(μ₃-η³-P(C ₆H₅)CH₂P-(C₆H₅)(C ₆H₄)) (3a), in which one Ru-Ru bond has been broken. 3a has been isolated in 82% yield upon crystallization at -30°C under a CO atmosphere. Similarly, 2 reacts at 0°C with phosphines to afford compounds of general formula Ru₃(CO)₉L(μ₃-η³-P(C ₆H₅)CH₂P(C₆H₅)(C ₆H₄)) (3b, L = P(C₆H₅)₃; 3c, L = dppm). Addition of triphenylphosphine to compound 2 at 25°C or warming a solution of 3a gives, among several compounds that have not been identified, the new dinuclear complex Ru₂(CO)₆(μ-η³-P(C₆H ₅)-CH₂P(C₆H₅)(C₆H ₄)) (5). The nature of compounds 3a, 3b 3c, and 5 has been established by spectroscopic means and for compound 3a, 3c, and 5 by X-ray diffraction methods. Crystal data: 3a, triclinic, C_i¹-P1, Z = 2, a = 13.435 (2) A?, b = 14.039 (2) A?, c = 9.839 (2) A?, α = 92.50 (1)°, β = 113.94 (1)°, γ = 92.86 (1)° (t = -165°C), final R(F) = 1.9%, NO = 5277, NV = 424; 3c, monoclinic, C_2h⁵-P2₁/c, Z = 4, a = 14.368 (2) A?, b = 25.612 (2) A?, c = 15.913 (2) A?, β = 108.09 (1)° (t = -150°C), final R(F) = 6.8%, NO = 6301, NV = 412; 5, monoclinic, C_2h⁵-P2₁/c, Z = 4, a = 13.625 (3) A?, b = 9.951 (2) A?, c = 18.917 (4) A?, β = 97.46 (2)° (t = -155°C), final R(F²) = 4.8%, NO = 4404, NV = 316.