Structural and Photochemical Properties of Organosilver Reactive Intermediates MeAg2 + and PhAg2

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 115; no. 33; pp. 9120 - 9127
• Main Authors: Brunet, C, Antoine, R, Broyer, M, Dugourd, P, Kulesza, A, Petersen, J, Röhr, M. I. S, Mitrić, R, Bonačić-Koutecký, V, O’Hair, R. A. J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 25.08.2011
• Subjects: A: Dynamics, Clusters, Excited States; Cations - chemistry; Chromogenic Compounds - chemistry; Chromogenic Compounds - metabolism; Electrons; Gases; Lasers; Mass Spectrometry; Models, Molecular; Organometallic Compounds - chemistry; Organometallic Compounds - metabolism; Photolysis - radiation effects; Silver Compounds - chemistry; Silver Compounds - metabolism; Static Electricity; Thermodynamics; Ultraviolet Rays
• ISSN: 1089-5639; 1520-5215; 1520-5215
• DOI: 10.1021/jp205716a

Although there is growing interest in silver promoted carbon–carbon bond formation, a key challenge in developing robust and reliable organosilver reagents is that thermal and photochemical decomposition reactions can compete with the desired coupling reaction. These undesirable reactions have been poorly understood due to complications arising from factors such as solvent effects and aggregation. Here the unimolecular decomposition reactions of organosilver cations, RAg2 +, where R = methyl (Me) and phenyl (Ph), are examined in the gas phase using a combination of mass spectrometry based experiments and theoretical calculations to explore differences between thermal and photochemical decompositions. Under collision-induced dissociation conditions, which mimic thermal decomposition, both PhAg2 + and MeAg2 + fragment via formation of Ag+. The new ionic products, RAg+• and Ag2 +•, which arise via bond homolysis, are observed when RAg2 + is subject to photolysis using a UV–vis tunable laser OPO. Furthermore, comparisons between the theoretical and experimental UV–vis spectra allow us to unambiguously determine the most stable structures of PhAg2 + and MeAg2 + and to identify the central role of the silver part in the optical absorption of these species. The new photoproducts result from fragmentation in electronic excited states. In particular, potential energy surface calculations together with the fragment charges highlight the role of triplet states in these new fragmentation schemes.