Mixed-ligand complexes of diruthenium (II, III): Syntheses and molecular structures of chloro-bis-(acetato)-bis-(2-anilinopyridinato)(2-anilinopyridine)diruthenium methylene chloride and chloro-(acetato)-tris(6-chloro-2-oxypyridinato)diruthenium methylene chloride

Abstract

The compound Ru₂Cl(O₂CCH₃)₂(PhNpy)₂(PhNHpy)·CH₂Cl₂ (1) was prepared by reacting Ru₂Cl(O₂CCH₃)₄ and PhNHpy (in 1:3 molar proportions) in boiling methanol and crystallized by slow evaporation of a solution of the compound in a CH₂Cl₂-hexane mixture. The compound Ru₂Cl(O₂CCH₃)(chp)₃·CH₂Cl₂ (2) was obtained in a similar way with a 1:4 molar proportion of starting acetate to Hchp. While 1 is dark blue in color, 2 is purple. Both compounds are soluble in common organic solvents other than hexane and are indefinitely stable in air. Compounds 1 and 2 crystallize in the triclinic space group P1 and the orthorhombic space group Pnma, respectively, with the following unit cell dimensions: 1, a = 12.093(2) Å, b = 12.143(3) Å, c = 14.357(3) Å, α = 94.94(2)°, β = 114.15(2)°, γ = 92.01(2)°, V = 1911(1) ų, and Z = 2;2, a = 16.912(5) Å, b = 15.975(4) Å, c = 10.329(6) Å, V = 2791(2) ų, and Z = 4. The structures of 1 and 2 were refined to R = 0.044 (R_w = 0.062) and R = 0.058 (R_w = 0.066), respectively. In 1, the diruthenium(II, III) unit is bridged by two acetate and two 2-anilinopyridine anionic ligands (both oriented in the same direction) in trans-disposition. The axial positions are occupied by a Cl anion and a neutral PhNHpy ligand. The metal atom bonded to two equatorial pyridine nitrogen atoms has the Cl axial coordination. The amine hydrogen atom of the other axial ligand is hydrogen bonded to one bridging acetate group. The Ru---Ru, Ru---Cl and Ru---N(axial) distances in 1 are 2.308(1) Å, 2.560(2) Å, and 2.457(6) Å, respectively. The Ru---N (equatorial) and Ru---O distances are in the ranges 2.024(5)-2.098(6) Å and 2.030(5)- 2.055(4) Å, respectively. In 2, a polar arrangement of three bridging chp ligands around the diruthenium(II, III) unit is also present, along with one bridging CH₃CO₂^- ligand. The ruthenium atom which is bonded to four oxygen atoms has an axially coordinated Cl ion. The axial site of the other ruthenium atom, which is bonded to three N and one O atoms, is empty because of the three Cl atoms of the chp ligands that project into this axial site. The Ru---Ru and Ru---Cl distances in 2 are 2.282(4) Å and 2.474(9) Å, respectively. The Ru---N and Ru---O distances lie in the ranges 2.06(2)-2.11(2) Å and 1.95(2)-2.03(2) Å, respectively. Electronic spectra of the solutions of 1 and 2 in CH₂Cl₂ display bands at 695 nm (ε = 6560 M^-1 cm^-1) and 535 nm (ε = 3990 M^-1 cm^-1), respectively.