Framework Conversion of Oxido-Bridged Dinuclear Ruthenium Complexes

Abstract

Syntheses, properties, and reactions of hydroxido- or oxido-bridged dinuclear ruthenium complexes bearing a tridentate auxiliary ligand, ethylbis(2-pyridylmethyl)amine (ebpma) or benzylbis(2-pyridylmethyl)amine (bbpma), have been investigated. Reduction reactions of a singly oxido-bridged diruthenium complex bearing ebpma, [{RuIII,IVCl2(ebpma)}2(μ-O)]+ ([2Cl]+), by zinc in acetonitrile afforded an acetonitrile-substituted singly oxido-bridged complex in the RuIII–RuIII isovalent state, [{RuIII,IIICl(NCCH3)(ebpma)}2(μ-O)]2+ ([2CH3CN]2+). Chlorido ligand abstraction reactions using silver salts have also been attempted. Through a reaction of [2Cl]+ with two equimolar amounts of AgNO3 in water–acetone, a singly oxido-bridged complex having an aqua and a hydroxido, [{RuIIICl(OH2)(ebpma)}(μ-O){RuIVCl(OH)(ebpma)}]2+ ([2H2O-OH]2+), was obtained. Reactions with four equimolar amounts of AgL (L = CH3COO– or NO3–) in water–acetone gave doubly oxido- and bidentate oxygen donor ligand-bridged diruthenium complexes of Ru(III)–Ru(IV), [{RuIII,IV(ebpma)}2(μ-O)2(μ-L)]2+ ([3L]2+; L = O2CCH3; [3CH3COO]2+, L = O2NO; [3NO3]2+). Reactions of [3L]2+ under acidic conditions afforded a corresponding one-protonated species having the {Ru2(μ-O)(μ-OH)} core. Reactivity and electronic structure of the oxido-bridged diruthenium complexes were studied by electrochemical, spectroscopic, and theoretical methods.