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 RU2(DMBA)(4)CL2 (1, DMBA = N,N'-dimethylbenzamidinate) was obtained via refluxing Ru-2(OAc)(4)Cl with dimethylbenzamidine in the presence of LICI and Et3N under ambient atmosphere, Metathesis reactions between 1 and MC2Y (M = Li and Na) yielded bis-alkynyl de vafives Ru-2(DMBA)(4)(C(2)y)(2) (y = SiMe3 (2a), H (2b), Ph (2c), and C2SiMe3 (3a)), and further desilylation of 3a using K2CO3 resulted in Ru-2(DMBA)(4)(C4H)(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) Angstrom 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) Angstrom) and 3b (1.952[5] Angstrom). 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.