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

We have synthesized the first silver(III) carbene complexes, (CF 3 ) 3 Ag(NHC), by direct reaction of the silver(III) fluoride precursor complex [PPh 4 ][(CF 3 ) 3 AgF] 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(CF 3 ) 4 ] - . The synthetic procedure reported is envisaged to enable access to carbene complexes of other late transition-metals in high oxidation states.