CRYSTAL STRUCTURE OF BIS(2,2′-BIPYRIDYL)MONOCHLOROCOPPER(II) HEXAFLUOROPHOSPHATE MONOHYDRATE AT 298 K AND THE ELECTRON SPIN RESONANCE SPECTRA OF SOME BIS(2,2′-BIPYRIDYL)COPPER(II) COMPLEXES TO 4.2 K

The crystal structure of the title compound [Cu(bipy)2Cl][PF6]·H2O (1)(bipy = 2,2′-bipyridyl) has been determined by X-ray diffraction, using diffractometer data collection. The structure was solved by the heavy-atom method and successive Fourier synthesis. Compound (1) crystallises in the monoclinic space group P21/n with a= 21.403(5), b= 12.235(3), c= 8.599(2)A, β= 92.68(2)°, and Z= 4. The CuN4Cl chromophore involves a near-regular trigonal bipyramidal stereochemistry, but with a significant distortion of the three in-plane angles from 120°(115.7, 123.8, and 120.5°). The poly-crystalline and single-crystal e.s.r. spectrum of (1) and a number of other 2,2′-bipyridyl complexes with [Cu(bipy)2X]n+ cations (X = Cl or I, n= 1; X = NH3, n= 2) are reported between 300 and 4 K. The molecular g tensors are consistent with a near-regular trigonal bipyramidal or square pyramidal distorted trigonal bipyramidal stereochemistry. As the e.s.r. spectra do not change significantly with temperature a dynamic behaviour in the sense of the pseudo-rotation of the Berry–Twist mechanism is not considered to operate.