Study of Monomeric Copper Complexes Supported by <i>N</i>-Heterocyclic and Acyclic Diamino Carbenes

Abstract

The thermal properties of a series of monomeric copper(I) hexamethyldisilazide complexes supported by N-heterocyclic and acyclic diamino carbenes were evaluated to study the impact of N-alkyl substituents and backbone character on volatility and thermal stability of copper amides. The series of complexes were either liquids or solids with melting points in the broad range of 45–184 °C. Vaporization rates were measured by stepped-isothermal TGA experiments and found to be between 110–170 °C. Enthalpies of vaporization were determined to be 63–90 kJ/mol. Temperatures for 1 Torr vapor pressure were estimated to be 143–172 °C, showing a general dependence on molecular weight. The imidazolylidene complexes were thermally unstable with convincing evidence indicating the unsaturated backbone as a point of weakness. The imidazolinylidene complexes showed excellent thermal stability with comparable results for the formamidinylidenes complexes. The steric parameter of the carbene, %VBur, was calculated for all complexes characterized by single crystal X-ray diffraction.