Isokinetic relationships at the thermal decomposition of tetranuclear copper(II)‐complexes

A dependence of the activation energy upon the extent of conversion has been discovered for the thermal decomposition of Cu 4 OCl 6 L 4 with piperidine (1), morpholine (2), and triphenylphosphine oxide (3) as the ligand (L). Within the interval of conversions 0–0.3 the process shows a decrease in the activation energy (230–130 (1), 130–50 (2), and 200–100 (3) kJ mol −1 ). The processes considered show an isokinetic relationship with T iso = 255 ± 15 K which corresponds to a vibrational frequency of v iso = 177 ± 10 cm −1 . This value accords well with IR absorption bands assigned to the stretching vibration in the trigonal CuCl 3 chromophore as predicted by theory. Based on this, an assumption about the CuCl 3 ‐group as a central site of the reaction can be made. The IR‐ and X‐ray data are presented to support the assumption made. © 1995 John Wiley & Sons, Inc.