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

Abstract

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, RAg(2)(+), 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 PhAg(2)(+) and MeAg(2)(+) fragment via formation of Ag(+). The new ionic products, RAg(+•) and Ag(2)(+•), which arise via bond homolysis, are observed when RAg(2)(+) 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 PhAg(2)(+) and MeAg(2)(+) 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.

UV Photodissociation Action Spectroscopy of Haloanilinium Ions in a Linear Quadrupole Ion Trap Mass Spectrometer

“…2. The (phenyl)Ag 2 + species was formed via collision induced decarboxylation of phenylCO 2 Ag 2 + as described in Ref [3]. There is good general agreement between the data, but the spectrum measured here reveals additional information, with our OPO photon range extending well into the 320 -400 nm region.…”

“…We describe the details of the optical arrangement, the synchronization of instrument timing and the development of a software application for controlling the experiment and the real-time PD spectral analysis. Presented with this are, to our knowledge, the first reported UV PD action spectra of 4-chloroanilinium, 4-bromoanilinium and 4-iodoanilinium and, in addition, a comparison of the photodissociation action spectrum of (phenyl)Ag 2 + to a literature spectrum [3]. These examples demonstrate the utility of this experimental arrangement to monitor the wavelength-dependent photodissociation efficiency of multiple fragmentation channels for mass selected ions.…”

“…As a benchmarking experiment to compare similar but not identical instrumentation and to demonstrate the performance of the instrumentation described here, the PD action spectrum of (phenyl)Ag 2 + is plotted along with a reported spectrum acquired on a similar instrumental configuration [3] and is presented in Fig. 2.…”

“…For biomolecules, and other molecules with suitably facile bonds, a PD action spectrum can provide rich details about the primary molecular structure, electronic excited states and conformation of ions in the gas-phase [1][2][3][4][5][6][7][8].…”

Formation and reactions of the 1, 8-naphthyridine (napy) ligated geminally dimetallated phenyl complexes [(napy)Cu2(Ph)]+, [(napy)Ag2(Ph)]+ and [(napy)CuAg(Ph)]+

“…21 The bonding arrangement in these oligomers typically involves twoelectron three-center bonding as exemplified for the PhCu 2 subunit in Scheme 1(f), with contribution 6a involving the combination of the C(sp 2 ) molecular orbital of the bridging aryl group with a mutually bonding combination of Cu orbitals. 22,23 Multistage mass spectrometry experiments 24,25 have been used to prepare and examine the reactivity of binuclear coinage metal organometallic cations, including the ''bare'' systems [CH 3 26,27 [RCCAg 2 ] þ , 28,29 [PhAg 2 ] þ , 30 and the ''ligated'' systems [(dppm)Au 2 (Ph)] þ . 31 We recently examined the role of substituents in the decarboxylation of 25 different coordinated aromatic carboxylates in binuclear complexes, [(napy)Cu 2 (O 2 CC 6 H 4 X)] þ , where napy ¼ 1,8-naphthyridine and X ¼ H and the ortho (o), meta (m) and para (p) isomers of F, Br, CN, NO 2 , CF 3 , OAc, Me and MeO.…”