M−C Bond Homolysis in Coinage‐Metal [M(CF₃)₄]⁻ Derivatives

Abstract

A comparative study of the homoleptic [M(CF₃ )₄ ]^- complexes of all three coinage metals (M=Cu, Ag, Au) reveals that homolytic M-C bond cleavage is favoured in every case upon excitation in the gas phase (CID-MS² ). Homolysis also occurs in solution by photochemical excitation. Transfer of the photogenerated CF₃ ^. radicals to both aryl and alkyl carbon atoms was also confirmed. The observed behaviour was rationalized by considering the electronic structure of the involved species, which all show ligand-field inversion. Moreover, the homolytic pathway constitutes experimental evidence for the marked covalent character of the M-C bond. The relative stability of these M-C bonds was evaluated by energy-resolved mass spectrometry (ERMS) and follows the order Cu<Ag≪Au. The qualitatively similar and rather uniform behaviour experimentally observed for all three coinage metals gives no ground to suggest variation in the metal oxidation state along the group.