Crystal structure and electronic properties of bis(2,2′-bipyridyl)-thiocyanatocopper(II) tetrafluoroborate

Abstract

The crystal structure of the title compound, [Cu(bipy)₂(NCS)][BF₄](1)(bipy = 2,2′-bipyridyl), has been determined by X-ray analysis. It crystallises in the monoclinic space group C2/c with a= 12.791 (3), b= 24.641 (4), c= 15.456(3)Å, β= 107.4(1)°, and Z= 8. The five-co-ordinate CuN₂N′₂N″ chromophore has a distorted bipyramidal stereochemistry related to a regular trigonal-bipyramidal stereochemistry by a distortion towards square pyramidal. The single-crystal e.s.r. spectra involve rhombic g values, R= 1.21 [(g₂–g₁)/(g₃–g₂) where g₁ < g₂ < g₃], and cannot be used to distinguish between a d_z² or d_x²–y² ground state, but the direction of the highest g value establishes that it correlates with the elongated Cu–N direction of the square-pyramidal distortion of the CuN₂N′₂N″ chromophore. This, together with the twin-peaked electronic reflectance spectra (11 170 and 14 120 cm^–1), suggests that the structure of (1) is best described as square-pyramidal distorted trigonal bipyramidal.