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)]2 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.