Fluoride Abstraction Induced by Tris(pentafluoroethyl)difluorophosphorane: A Convenient Way to Synthesize Cationic N-Heterocyclic Carbene- and Cyclic (Alkyl)(amino)carbene-Ligated Copper Alkyne and Arene Complexes

Abstract

We herein report the convenient synthesis of different N-heterocyclic carbene (NHC)-and cyclic (alkyl)(amino)carbene (cAAC)-ligated copper cations using the weakly coordinating tris(pentafluoroethyl)trifluorophosphate counterion (FAP anion, [(C 2 F 5 ) 3 PF 3 ] − ). The reaction of the fluorido complexes [(carbene)CuF] (carbene = NHC, cAAC Me ) 2a−2f and the tris(pentafluoroethyl)difluorophosphorane (C 2 F 5 ) 3 PF 2 in the presence of alkynes or arenes led to fluoride transfer from Cu to the phosphorane with formation of the cationic transition metal complexes [(carbene)Cu(L)] + and the weakly coordinating counteranion [(C 2 F 5 ) 3 PF 3 ] − (FAP). Using this method, the complexes [(IDipp)Cu(L)] + FAP − (IDipp = 1,3-bis(2,6-di-isopropylphenyl)-imidazolin-2-ylidene; L = PhC�CPh, 4d; PhC�CMe, 5d), [(cAAC Me )Cu(L)] + FAP − (cAAC Me = 1-(2,6-di-isopropylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene; L = PhC�CPh, 4f; PhC�CMe, 5f), [(SIDipp)Cu(C 6 Me 6 )] + FAP − (6e), (SIDipp = 1,3-bis(2,6-di-iso-propylphenyl)-imidazolidine-2-ylidene), and [(cAAC Me )Cu(C 6 Me 6 )] + FAP − (6f) have been synthesized and characterized. The complexes [(IDipp)Cu(C 6 Me 6 )] + FAP − (6d) and [(cAAC Me )Cu(C 6 Me 6 )] + FAP − (6f) have been used as catalysts for the copper(I)-catalyzed cycloaddition of benzyl azide to terminal alkynes.