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

• Published in: Angewandte Chemie International Edition Vol. 58; no. 29; pp. 9954 - 9958
• Main Authors: Baya, Miguel, Joven‐Sancho, Daniel, Alonso, Pablo J., Orduna, Jesús, Menjón, Babil
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 15.07.2019
• Edition: International ed. in English
• Subjects: Aromatic compounds; coinage metals; Comparative studies; Copper; Electronic structure; Excitation; Gold; homolysis; ligand-field inversion; Mass spectrometry; Mass spectroscopy; Metals; Oxidation; Photochemicals; radicals; Silver; Stability analysis; trifluoromethyl substituents; Valence; Vapor phases; coinage metals; ligand-field inversion; radicals; trifluoromethyl substituents; homolysis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201903496

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. Coinage‐metal compounds [M(CF3)4]− release CF3. radicals under both thermal and photochemical activation as a result of the ligand‐field inversion phenomenon. The M−C bond strength follows the order Cu<Ag≪Au.