The Fluoride Method: Access to Silver(III) NHC Complexes

Abstract

We have synthesized the first silver(III) carbene complexes, (CF3)3Ag(NHC), by direct reaction of the silver(III) fluoride precursor complex [PPh4][(CF3)3AgF] with different imidazolium salts. This novel methodology circumvents the use of free NHC molecules. The silver(III) carbene complexes thus prepared are unprecedented and show remarkable thermal stabilities. They display square‐planar or square‐pyramidal geometry. Following our calculations, the electronic structure of a model representative complex exhibits Inverse Ligand Field (ILF). The compounds reported herein are synthetic analogues of the elusive difluorocarbene and carbonyl species proposed as intermediates in the acidic decomposition of [Ag(CF3)4]−. The synthetic procedure reported is envisaged to enable access to carbene complexes of other late transition‐metals in high oxidation states.

Elementary Steps of Silver- and Gold-Mediated Trifluoromethylation Reactions

“…For silver, completely analogous high-valent [Ag(R)(CF 3 ) 3 ] − complexes are known as well (Scheme , middle, R = aryl), , besides several other related species. − Like their cuprate congeners, the [Ag(R)(CF 3 ) 3 ] − complexes also furnish the RCF 3 cross-coupling products at slightly elevated temperatures. First mechanistic studies indicate the coupling to proceed via a concerted reductive elimination .…”