Synthesis, Reactivity, and Bonding of Gold(I) Fluorido–Phosphine Complexes

Abstract

Gold­(I) fluorido complexes with phosphine ligands have been synthesized from their respective iodido precursors. The bonding situation in comparison between complexes bearing phosphines and N-heterocyclic carbenes (NHCs) was explored quantum-chemically, obtaining similar results for both. Calculations of the 19F NMR chemical shifts match the experimental values well, including the approximately 40 ppm low-field shifts for the phosphine complexes compared to the NHC complexes, in spite of similar negative charges on fluorine. The reactivity of the highly water-sensitive gold­(I) fluorido complexes was studied, resulting in substitution at the metal using trimethylsilyl reagents. The compounds studied were characterized using NMR as well as X-ray diffraction methods.

Au(I) Fluorido Phosphine Complexes: Tools for the Hydrofluorination of Alkynes

“…In general, when compared to NHC complexes, phosphine complexes showed a diminished reactivity towards alkynes to generate vinyl compounds, although the electronic structures of complexes [Au(F)(L)] (L = NHC, phosphine) are comparable according to DFT calculations. [10] The obtained complexes 4-6 exhibit analogous spectroscopic data as found for the vinyl compound 2, with 4 J FP coupling constants of 40 Hz. As in the reaction with 1-phenyl-1propyne, a huge excess of the alkynes is required to obtain notable conversions.…”

“…With an excess of 2‐butyne the vinyl complex [Au(CH 3 C=C(F)CH 3 )(SPhos)] ( 6 ) was generated, but a vinyl complex from the reaction with 1,1,1,4,4,4‐hexafluorobutyne was not observed, even not at elevated temperatures. In general, when compared to NHC complexes, phosphine complexes showed a diminished reactivity towards alkynes to generate vinyl compounds, although the electronic structures of complexes [Au(F)(L)] (L=NHC, phosphine) are comparable according to DFT calculations [10] . The obtained complexes 4 – 6 exhibit analogous spectroscopic data as found for the vinyl compound 2 , with 4 J FP coupling constants of 40 Hz.…”

“…Elemental analyses (EA) were performed with a HEKAtech Euro EA Elemental Analyzer. OP(4‐C 6 H 4 F) 3 , [25] [(Me 2 N) 3 P] 2 N + F − , [22] [Au(Cl)(SIPr)], [26] [Au(Cl)(SPhos)], [27] [Au(I)(SPhos)] ( 19 ), [10] [Au(SPhos)][B(C 6 F 5 ) 4 ] ( 17 ) [28] and [Au(F)(SPhos)] ( 1 ) [10] were synthesized according to previously reported protocols.…”

“…In this paper we will present reactivity studies at Au(I) fluorido phosphine complexes [10] towards alkynes. Studies on the formation of fluorovinyl complexes allowed for a further understanding of key‐steps in hydrofluorination reactions with Au(I) catalysts.…”

“…[5a] In a recent contribution towards the hydrofluorination of terminal alkynes, the compound [{Au(SIPr)} 2 μ-OH][FHF] as well as mono-and binuclear alkynyl species were identified as potential intermediates. [6b] In this paper we will present reactivity studies at Au(I) fluorido phosphine complexes [10] towards alkynes. Studies on the formation of fluorovinyl complexes allowed for a further understanding of key-steps in hydrofluorination reactions with Au(I) catalysts.…”