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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) Å, 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) Å, whereas the Ru-N bond involving the central N atom has the much shorter length of 1.939 (7) Å 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) Å and the intra-molecular distance between Ru centers is 6.579 (4) Å. In the crystal, weak C-H⋯Cl and C-H⋯F inter-actions consolidate the packing.

We report the structural characterization of [6',6''-bis-(pyridin-2-yl)-2,2':4',4'':2'',2'''-quaterpyridine](2,2'-bi-pyridine)-chlorido-ruthenium(II) hexa-fluorido-phosphate, [RuCl(C10H8N2)(C30H20N6)]PF6, which contains the bidentate ligand 2,2'-bi-pyridine (bpy) and the tridendate ligand 6',6''-bis-(pyridin-2-yl)-2,2':4',4'':2'',2'''-quaterpyridine (tpy-tpy). The [RuCl(bpy)(tpy-tpy)](+) monocation has a distorted octa-hedral geometry at the central Ru(II) ion due to the restricted bite angle [159.32 (16)°] of the tridendate ligand. The Ru-bound tpy and bpy moieties are nearly planar and essentially perpendicular to each other with a dihedral angle of 89.78 (11)° between the least-squares planes. The lengths of the two Ru-N bonds for bpy are 2.028 (4) and 2.075 (4) Å, with the shorter bond being opposite to Ru-Cl. For tpy-tpy, the mean Ru-N distance involving the outer N atoms trans to each other is 2.053 (8) Å, whereas the length of the much shorter bond involving the central N atom is 1.936 (4) Å. The Ru-Cl distance is 2.3982 (16) Å. The free uncoordinated moiety of tpy-tpy adopts a trans,trans conformation about the inter-annular C-C bonds, with adjacent pyridyl rings being only approximately coplanar. The crystal packing shows significant π-π stacking inter-actions based on tpy-tpy. The crystal structure reported here is the first for a tpy-tpy complex of ruthenium.

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.

The title heteroleptic bis--terpyridine complex, [Ru(C(15)H(11)N(3))(C(17)H(11)N(3))](PF(6))(2)·2CH(3)CN, crystallized from an acetonitrile solution as a salt containing two hexa-fluoridophosphate counter-ions and two acetonitrile solvent mol-ecules. The Ru(II) atom has a distorted octa-hedral geometry due to the restricted bite angle [157.7 (3)°] of the two mer-arranged N,N',N''-tridendate ligands, viz. 2,2':6',2''-terpyridine (tpy) and 4'-ethynyl-2,2':6',2''-terpyridine (tpy'), which are essentially perpendicular to each other, with a dihedral angle of 87.75 (12)° between their terpyridyl planes. The rod-like acetyl-ene group lies in the same plane as its adjacent terpyridyl moiety, with a maximum deviation of only 0.071 (11) Å from coplanarity with the pyridine rings. The mean Ru-N bond length involving the outer N atoms trans to each other is 2.069 (6) Å at tpy and 2.070 (6) Å at tpy'. The Ru-N bond length involving the central N atom is 1.964 (6) Å at tpy and 1.967 (6) Å at tpy'. Two of the three counter anions were refined as half-occupied.