Diphosphine ring expansion and ?-bond reduction in the reaction between 1,2-bis(diphenylphosphino) cyclobutenedione (bpcbd) and Ru3(CO)10(MeCN)2: X-ray diffraction structures of Ru3(CO)10[2,3- bis(diphenylphosphino)succinic anhydride] and Ru2(CO)6(bma)

Abstract

Replacement of the acetonitrile ligands in Ru3(CO)10(MeCN)2 by the diphosphine ligand 1,2-bis(diphenylphosphino)cyclobutenedione (bpcbd) initially gives the unstable bpcbd-bridged cluster Ru3(CO)10(bpcbd) (1), followed by its subsequent transformation to the triruthenium cluster Ru3(CO)10(bma) (2). The decomposition of cluster 2 serves to produce the ruthenium compounds Ru3(CO)10[2,3-bis(diphenylphosphino)succinic anhydride] (3) and Ru2(CO)6(bma) (4). Compounds 2–4 provide the experimental evidence for the ring expansion of the cyclobutenedione ring via the formal insertion of an oxygen atom into the four-membered ring and hydrogen addition to the π bond upon exposure to the atmosphere and/or moisture. Both 3 and 4 have been isolated and characterized in solution by IR and 31P NMR spectroscopies, and the molecular structure of each product has been verified by X-ray crystallography. Ru3(CO)10[2,3-bis(diphenylphosphino)succinic anhydride] crystallizes, as the CH2Cl2 solvate, in the monoclinic space group P21/c, a = 12.178(2)A, b = 15.988(2)A, c = 22.472(3)A, β = 95.115(2)°, V = 4358(1)A3, Z = 4, and dcalc = 1.732 Mg/m3; R = 0.0344, Rw = 0.0931 for 5683 reflections with I > 2σ(I). The dinuclear compound Ru2(CO)6(bma) crystallizes in the triclinic space group P-1, a = 9.298(3)A, b = 12.020(3)A, c = 30.858(8)A, α = 81.774(5)°, β = 89.276(5)°, γ = 83.545(4)°, V = 3391(1)A3, Z = 4, and dcalc = 1.730 Mg/m3; R = 0.0670, Rw = 0.1444 for 8766 reflections with I > 2a(I).