X-Ray Crystal Structures of 2,2'-Bis(pyrazol-1-yl)-4,4'-bipyridine and a Tetramethyl Derivative; New Bis-bidentate Binucleating Ligands

Abstract

X-Ray crystal structures of 2,2°-bis(pyrazol-1-yl)-4,4°-bipyridine (3) and 2,2°-bis(3,5-dimethyl-pyrazol-1-yl)-4,4°-bipyridine (4) have been determined at 130 K. Crystals of (3) are triclinic, Pī , a 8.061(1), b 9.024(1), c 10.680(1)Ǻ, α 102.032(8), β 107.931(6), γ 107.355(7)°, Z = 2; the structure was refined to a conventional R(I > 2σ(I)) = 0.0273. Crystals of (4) are orthorhombic, P 2₁2₁2₁, a 7.077(2), b 13.906(4), c 16.697(5) Ǻ, Z = 4; the structure was refined to a conventional R(I > 2σ(I)) = 0.0386. In both molecules there is significant (33±1°) twisting about the central pyridine-pyridine bond. The pyrazole rings of (3) are approximately coplanar (6±2°) with their attached pyridine rings, while in (4) the methyl groups induce slightly greater deviations from coplanarity (15±3°). Factors which influence the solid-state conformations and molecular packing of these molecules are discussed.