Pendant-bridging-chelating-cleavage: A series of bonding modes in ruthenium(II)-BINAPO complexes
Reaction of 1,1'-bis(diphenylphosphino)binaphthol (BINAPO, 1) with [RuCl2(η6-arene)]2 in methanol leads to dinuclear BINAPO-bridged Ru compounds [{RuCl2(η6-p-cymene)}2-(μ-BINAPO)], 2a, in near quantitative yield. In dichloromethane or acetonitrile, 1 preferably affords mononuclear species in which one of the phosphine centers remains uncoordinated. These complexes can be further stabilized by reaction with BH3 to afford, for example, [RuCl2(η6-p-cymene)(η1-BINAPO-BH3)], 4a. Upon heating a mixture of 1 and RuCl2(η6-p-cymene) in DMF, P-O bond cleavage occurs to afford [RuCl(η2-PPh2-BINOL)(η6-p-cymene)], 5a, bearing an anionic PO-chelating ligand. Ligand 1 acts as an intact chelate when reacted with [Ru2(μ-Cl)3(η6-p-cymene)2][PF6] to yield [RuCl(η6-p-cymene)(η2-BINAPO)][PF6], 7. Reaction of 1 with [RuCp(CH3CN)3] [PF6] in acetonitrile or chloroform affords [{RuCp(CH3CN)2}2(μ-BINAPO)][PF6]2, 8, and [RuCp(CH3CN)(η2 -BINAPO)][PF6], 9, respectively. The solid-state structures of 1, 2a, 4a, and 7 are reported, that of 2a representing a rare structural example of a molecule with a bridging binaphthyl-type ligand.