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.
Keywords: coinage metals; homolysis; ligand-field inversion; radicals; trifluoromethyl substituents.
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