Photoinitiated Oxidative Addition of CF₃I to Gold(I) and Facile Aryl-CF₃ Reductive Elimination

Abstract

Herein we report the mechanism of oxidative addition of CF3I to Au(I), and remarkably fast Caryl–CF3 bond reductive elimination from Au(III) cations. CF3I undergoes a fast, formal oxidative addition to R3PAuR′ (R = Cy, R′ = 3,5-F2-C6H4, 4-F-C6H4, C6H5, 4-Me-C6H4, 4-MeO-C6H4, Me; R = Ph, R′ = 4-F-C6H4, 4-Me-C6H4). When R′ = aryl, complexes of the type R3PAu(aryl)(CF3)I can be isolated and characterized. Mechanistic studies suggest that near-ultraviolet light (λmax = 313 nm) photoinitiates a radical chain reaction by exciting CF3I. Complexes supported by PPh3 undergo reversible phosphine dissociation at 110 °C to generate a three-coordinate intermediate that undergoes slow reductive elimination. These processes are quantitative and heavily favor Caryl–I reductive elimination over Caryl–CF3 reductive elimination. Silver-mediated halide abstraction from all complexes of the type R3PAu(aryl)(CF3)I results in quantitative formation of Ar–CF3 in less than 1 min at temperatures as low as −10 °C.

Secondary kinetic deuterium isotope effect in oxidative addition reaction of cycloplatinated(II) complexes with MeI

“…2-In 31 P NMR spectra of the starting organoplatinum(II) complexes [PtMe(ppy) (P(OPh) 3 The known organoplatinum(IV) complex [PtMe 2 I(ppy) (PPh 3 )], 2a (reported previously [17]), was further identified by single crystal Xeray diffraction analysis (Fig. 3).…”

“…The starting complexes [PtMe(C^N)L], 1a, 1b and 1d, in which C^N ¼ 2-phenylpyridinate (ppy) or benzo[h]quinolinate (bhq), and L ¼ PPh 3 , or PMePh 2 , were synthesized according to literature [17,18]. The new analogous complexes [PtMe(ppy) (P(OPh) 3 )], 1c, and [PtMe(bhq) (P(OPh) 3 )], 1e, were prepared similarly by the reaction of [PtMe(ppy) (SMe 2 )] or [PtMe(bhq) (SMe 2 )], respectively, with 1 equiv P(OPh) 3 . Either of these starting methylplatinum(II) complexes, 1ae1e, was reacted cleanly with an excess of MeI in acetone at room temperature giving a very pale yellow solution, from which the thermodynamic isomer product [PtMe 2 I(C^N)L], 2ae2e, was obtained (see Scheme 1) [17].…”

“…Structures of the new P(OPh) 3 analogous organoplatinum(II) complexes [PtMe(ppy) (P(OPh) 3 )], 1c, and [PtMe(bhq) (P(OPh) 3 )], 1e, in solution were readily characterized from their 1 H and 31 P NMR spectra. Typically, in the 1 H NMR spectrum of 1c in CDCl 3 at room temperature (see Fig.…”

“…1-When the Pt(II) complex [PtMe(ppy) (P(OPh) 3 )], 1c, is reacted with excess CD 3 I, it was possible to confirm that the two methyl ligands, CH 3 and CD 3 , are rapidly exchanged during the reaction to finally give the Pt(IV) product complex 2c, as a 1:1 mixture of [PtMeCD 3 I(ppy) (P(OPh) 3 )], in which CD 3 is trans to P(OPh) 3 ligand and Me is trans to N of ppy ligand, and [PtCD 3 MeI(ppy) (P(OPh) 3 )], in which Me is trans to P(OPh) 3 ligand and CD 3 is trans to N of ppy ligand.…”

“…The cyclometalated platinum(II) complexes with a rather electron rich Pt(II) centers were the substrates of choice because they are potentially capable of reacting by different mechanisms such as S N 2 (producing the kinetically trans addition product) or concerted three-center one (directly producing the cis addition product) [9,10]. Thus, we studied secondary a-deuterium KIEs in oxidative addition reaction of the cycloplatinated(II) complexes [PtMe(C^N) (L)], in which C^N ¼ 2-phenylpyridinate (ppy) or benzo[h]quinolinate (bhq) and L ¼ PPh 3 , PMePh 2 or P(OPh) 3 , with CH 3 I/CD 3 I. We studied kinetics of these reactions by using UVevis spectroscopy and determined the KIEs, showing that nature of the ancillary ligands containing phosphorous donor atoms and the cycloplatinated ligands, C^N, are not effective on the values of KIEs (k H /k D ).…”