Tetrakis(N,N‘-dimethylbenzamidinato)diruthenium(III) Compounds Bearing Axial Chloro and Alkynyl Ligands: A New Family of Redox Rich Diruthenium Compounds

Novel diruthenium(III) compound Ru(2)(DMBA)(4)Cl(2) (1, DMBA = N,N'-dimethylbenzamidinate) was obtained via refluxing Ru(2)(OAc)(4)Cl with dimethylbenzamidine in the presence of LiCl and Et(3)N under ambient atmosphere. Metathesis reactions between 1 and MC(2)Y (M = Li and Na) yielded bis-alkynyl derivatives Ru(2)(DMBA)(4)(C(2)Y)(2) (Y = SiMe(3) (2a), H (2b), Ph (2c), and C(2)SiMe(3) (3a)), and further desilylation of 3a using K(2)CO(3) resulted in Ru(2)(DMBA)(4)(C(4)H)(2) (3b). Compound 1 is paramagnetic (S = 1), while compounds 2 and 3 are diamagnetic. The single-crystal X-ray diffraction study revealed that the Ru-Ru distances are 2.3224(7), 2.4501(6), and 2.4559(6) A for 1, 2a, and 3b, respectively. A strong Ru-C sigma-bond in alkynyl adducts was implied by the short Ru-C distances in 2a (1.955(4) A) and 3b (1.952[5] A). All the compounds undergo three one-electron redox processes, an oxidation and two reductions, and the reversibility of redox couples depends on the nature of axial ligands.