Pyrazine-Coordinated Dinuclear and Mononuclear Ruthenium Complexes Formed via the Conversion of the Triply Chlorido-Bridged Diruthenium(II) Complex

The pyrazine-coordinated dinuclear and mononuclear ruthenium complexes were synthesized through the framework conversion reactions of the triply chlorido-bridged diruthenium(II) complex [{RuII,II(bbpma)}2(μ-Cl)3]+ (bbpma; benzylbis(2-pyridylmethyl)amine, [1]+) in the presence of pyrazine, which could function as the simple molecular multinucleation ligand of metal compounds. A reduction reaction of fac-[RuIIICl3(bbpma)] with zinc in the presence of hydrochloric acid afforded [1]+ in solution, and the following addition of pyrazine (1 equiv) in the solution led to the formation of a singly pyrazine (pz)-bridged diruthenium complex, [{RuII,II(μ-Cl2ZnCl2)(bbpma)}2(μ-pz)] ([2(II,II)(ZnCl2)2]). The stoichiometric two-electron oxidation of [2(II,II)(ZnCl2)2] was successfully proceeded, and a Ru(III)–Ru(III) species, [{RuIII,IIICl2(bbpma)}2(μ-pz)](PF6)2 ([III,III](PF6)2), was isolated. The reaction of [1]+ with excess amounts of pyrazine without hydrochloric acid afforded mononuclear Ru(III) and Ru(II) complexes containing one or two pyrazine, fac-[RuClm(pz)3–m(bbpma)]+ (m = 2; [3]+; m = 1; [4]+). The details of the electrochemical and spectroscopic properties of [1]+–[4]+ in organic and aqueous solutions were discussed.