A crystallographic, EPR and theoretical study of the Jahn–Teller distortion in [CuTp2] (Tp− = tris{pyrazol-1-yl}hydridoborate)
Abstract
Crystals of the title compound (1) contain two independent, centrosymmetric half-molecules per asymmetric unit. While both of these show Jahn–Teller elongated six-coordinate geometries, the lengths of the elongated Cu–N bonds in the two molecules differ by 0.117(2)
Å at 30 K. The structure of one of these molecules (molecule A) does not vary with temperature below 350 K. The other molecule (molecule B) shows Cu–N bond lengths that are temperature-dependent between 225 and 375 K, but do not vary further at lower temperature. This indicates a fluxional axis of Jahn–Teller elongation in this molecule at these higher temperatures. Consideration of the thermal parameters in these structures implies that the fluxionality in molecule B is frozen out near 150 K. This conclusion is supported by a Q-band powder