(2,2'-Bi-pyridine)-chlorido-[diethyl (2,2':6',2''-terpyridin-4-yl)phospho-nate]ruthenium(II) hexa-fluorido-phosphate aceto-nitrile/water solvate.

The cationic complex in the title compound, [RuCl(C10H8N2)(C19H20N3O3P)]PF6·0.83CH3CN·0.17H2O, is a water-oxidation precatalyst functionalized for TiO2 attachment via terpyridine phospho-nate. The The Ru(II) atom in the complex has a distorted octa-hedral geometry due to the restricted bite angle [159.50 (18)°] of the terpyridyl ligand. The dihedral angle between the least-squares planes of the terpyridyl and bipyridyl moieties is 86.04 (14)°. The mean Ru-N bond length for bi-pyridine is 2.064 (5) Å, with the bond opposite to Ru-Cl being 0.068 Å shorter. For the substituted terpyridine, the mean Ru-N distance involving the outer N atoms trans to each other is 2.057 (6) Å, whereas the bond length involving the central N atom is 1.944 (5) Å. The Ru-Cl distance is 2.4073 (15) Å. The P atom of the phospho-nate group lies in the same plane as its adjacent pyridyl ring, with the ordinary character of the bond between P and Ctpy [1.801 (6) Å] allowing for free rotation of the terpyridine substituent around the P-Ctpy axis. The aceto-nitrile solvent mol-ecule was refined to be disordered with two water mol-ecules; occupancies for the acetontrile and water mol-ecules were 0.831 (9) and 0.169 (9), respectively. Also disordered was the PF6 (-) counter-ion (over three positions) and one of the eth-oxy substituents (with two positions). The crystal structure shows significant intra- and inter-molecular H⋯X contacts, especially some involving the Cl(-) ligand.