Chemical bonding in metalaheterocumulene complexes : II Demonstration of a temperature dependant conformational disorder of the methyl groups in [(CO)5CrNCN(C2H5)2]

Abstract

During the determination of the crystal structure of [(CO)5CrNCN(C2H5)2] by neutron diffraction, a remarkable te temperature-dependance of the intensity of three reference reflections between 100 and 300 K was accidentally observed. In order to try to understand the nature of this phenomenon, the behaviour of this compound as a function of the temperature has been studied by differential calorimetry, and by power and single crystal X-ray diffraction methods. These experiments show neither a phase transition nor a crystal space group modification. The experimental results, supported by a simplified model, suggest a rotational disorder of the methyl groups near room temperature.