Synthesis of Bidentate sigma-Borane-Ruthenium Complexes [Cp*Ru((PPr3)-Pr-i)(eta(2)-BH3 center dot L)](+) (L = Amines or Phosphines): Structures, Properties, and Reactivities

摘要

Chloride abstraction from [Cp*RuCl((PPr3)-Pr-i)] using Na[BAr(f)4] in the presence of BH3 center dot L afforded bidentate sigma-borane complexes [Cp*RuCl((PPr3)-Pr-i)(eta(2)-BH3 center dot L)][BAr(f)4], where L = quin (N(C2H4)(3)CH), NMe3, NHMe2, (NHPr2)-Pr-i, NH2Me, PMe3, PMe2Ph; Cp*=eta(5)-C5Me5; [BAr(f)4] = [B{3,5-C6H3(CF3)(2)}(4)]. In these compounds, the borane ligand is coordinated to the ruthenium atom through two B-H-Ru three-center two-electron bonds. Phosphine-borane complexes exhibit fluxional behavior due to the site exchange between the bridging and terminal BH hydrogen atoms at room temperature. Secondary amine-borane derivatives release H-2 on heating. BH3 center dot NHMe2 and BH3 center dot(NHPr2)-Pr-i undergo dehydrogenation even with use of a catalytic amount of [Cp*RuCl((PPr3)-Pr-i)] and Na[BAr(f)4] to ultimately yield [BH2NMe2](2) and BH2=(NPr2)-Pr-i, respectively.