Crystal structure and redox potentials of the tppz-bridged {RuCl(bpy)}(+) dimer.

We report the structural and electrochemical characterization of the binuclear complex [μ-(C(24)H(16)N(6)){RuCl(C(10)H(8)N(2))}(2)](PF(6))(2), which contains the bis-tridentate bridging ligand 2,3,5,6-tetra-kis-(pyridin-2-yl)pyrazine (tppz), the monodentate ligand Cl(-), and the bidentate ligand 2,2'-bi-pyridine (bpy) {systematic name: μ-2,3,5,6-tetra-kis-(pyridin-2-yl)pyrazine-bis-[(2,2'-bi-pyridine)-chlorido-ru-thenium(II)] bis-(hexa-fluorido-phosphate)}. The complete [(bpy)(Cl)Ru(tppz)Ru(Cl)(bpy)](2+) dication is generated by crystallographic twofold symmetry; the tppz bridging ligand has a significantly twisted conformation, with an average angle of 42.4° between the mean planes of adjacent pyridyl rings. The metal-coordinated chloride ligands are in a trans configuration relative to each other across the {Ru(tppz)Ru} unit. The Ru(II) ion exhibits a distorted octa-hedral geometry due to the restricted bite angle [160.6†(3)°] of the tppz ligand. For bpy, the bond lengths of the Ru-N bonds are 2.053†(8) and 2.090†(8)†à , with the shorter bond being opposite to Ru-Cl. For the tridentate tppz, the Ru-N distances involving the outer N atoms trans to each other are 2.069†(8) and 2.072†(9)†à , whereas the Ru-N bond involving the central N atom has the much shorter length of 1.939†(7)†à as a result of the geometric constraints and stronger π-acceptor ability of the pyrazine-centered bridge. The Ru-Cl distance is 2.407†(3)†à and the intra-molecular distance between Ru centers is 6.579†(4)†à . In the crystal, weak C-H⋯Cl and C-H⋯F inter-actions consolidate the packing.