Syntheses, molecular structures and electrochemical behavior of two isomeric Ru(PhNpy)<SUB>2</SUB>(PPh<SUB>3</SUB>)<SUB>2</SUB> complexes

The title compounds, isomers of Ru(PhNpy)<SUB>2</SUB>(PPh<SUB>3</SUB>)<SUB>2</SUB> (PhNpy = the anion of 2-(N-anilino)-pyridine), having C<SUB>1</SUB> and C<SUB>2</SUB> symmetry, were prepared by reacting RuCl<SUB>2</SUB>(PPh<SUB>3</SUB>)<SUB>3</SUB> with LiPhNpy in toluene. The crystal and molecular structures of these compounds have been determined from three-dimensional X-ray study. Both compounds crystallize in the monoclinic space group P2<SUB>1</SUB>/c with the following unit cell dimensions: C<SUB>1</SUB>-isomer: A = 13.852(3), B = 18.872(3), C = 18.206(3), &#946; = 84.32(5), V = 4736(2) and Z = 4. C<SUB>2</SUB>-isomer: A = 11.166(9), B = 20.404(8), C = 20.716(16), &#946; = 97.14(7), V = 4683(10) and Z = 4. The structures were refined to R = 0.053 (Rw = 0.083) for the C<SUB>1</SUB>-isomer and R = 0.055 (R<SUB>w</SUB> = 0.063) for the C<SUB>2</SUB>-isomer. In the C<SUB>1</SUB>-isomer, the coordinating atoms N-py, N-Ph and PPH<SUB>3</SUB> are all in cis-arrangement. In the C<SUB>2</SUB>-isomer, the py-rings are trans to each other. The complexes are six-coordinate with four-membered chelate rings. The N---Ru---N angle in the chelate rings is ca. 62&#176; in each case. The Ru---P bond lengths lie in the range 2.286(3)-2.337(1) &#197;. The average Ru---N(py), and Ru---N(Ph) bond lengths are 2.083 &#197; and 2.171 &#197;, respectively. Dichloromethane solutions of the C<SUB>1</SUB> and C<SUB>2</SUB> isomers display two quasireversible oxidation waves at 0.480, 1.175 V and 0.290, 1.040 V, respectively. The responses have one-electron stoichiometry and are assignable to Ru<SUB>III</SUB>/Ru<SUB>II</SUB> and Ru<SUB>IV</SUB>/Ru<SUB>III</SUB> couples