Tris(pentafluoroethyl)difluorophosphorane for fluoride abstraction and ligand exchange reactions of N-heterocyclic carbene and cyclic alkyl(amino)carbene copper(I) fluorides.

The synthesis and structural characterization of a variety of N-heterocyclic carbene (NHC)- and cyclic (alkyl)(amino)carbene (cAAC)-ligated cationic copper(I) complexes, featuring the weakly coordinating tris(pentafluoroethyl)trifluorophosphate counteranion (FAP- anion, [(C2F5)3PF3]-) are reported. Starting with the complex [(IDipp)Cu(C6Me6)]+FAP- (IIa) reported previously, (S. A. Föhrenbacher, M. J. Krahfuss, L. Zapf, A. Friedrich, N. V. Ignat'ev, M. Finze and U. Radius, Chem. - Eur. J., 2021, 27, 3504-3516) a series of mononuclear complexes [(IDipp)Cu(LB)]+FAP- (IDipp = 1,3-bis(2,6-di-iso-propylphenyl)-imidazolin-2-ylidene) were obtained via ligand exchange of C6Me6 with neutral two valence electron (2 VE) donor molecules (LB = NH3, 1; C6H12N2 = DABCO, 2; C7H10N2 = DMAP, 3; C4H4N2 = pyrazine, 4; C13H9N = acridine, 5; η1-OC13H9N = acridone, 6; C4H10S = SEt2, 7; C4H8S = THT, 8; PCy3, 9), alongside the dinuclear species [{(IDipp)Cu}2(C2N3H3)2]2+2FAP- (10) with 1,2,4-triazole. In a parallel strategy, [(cAACMe)Cu(C6Me6)]+FAP- (IIb) was employed as precursor for Cu(I) complex formation, leading to [(cAACMe)Cu(LB)]+FAP- (LB = C7H10N2, 13; C4H10S, 14) and the dinuclear complexes [{(cAACMe)Cu}2(C6H12N2)]2+2FAP- (11) and [{(cAACMe)Cu}2(C4H4N2)]2+2FAP- (12). Additionally, the reaction of [(carbene)CuF] with (C2F5)3PF2 in the presence of different 2 VE donor ligands induced fluoride replacement with a 2 VE donor ligand (LB). This strategy facilitated the isolation of a broad range of complexes of the type [(carbene)Cu(LB)]+FAP-, including [(IDipp)Cu(LB)]+FAP- (LB = (NCMe)2, 16; NCPh, 17; NH2Ph, 18; NHPh2, 21; NC5H5, 22; NC5H3F2, 24; NC5H2F3, 25; η1-OCPh2, 27), [(SIDipp)Cu(NH2Ph)]+FAP- (19) (SIDipp = 1,3-bis(2,6-di-iso-propylphenyl)-imidazolidin-2-ylidene) and [(cAACMe)Cu(LB)]+FAP- (cAACMe = 1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene; LB = NCMe, 15; NH2Ph, 20; NC5H5, 23; THF, 28). Additionally, the dinuclear complex [{(IDipp)Cu(μ-ONC5H5)}2]2+2FAP- (26) was obtained upon reaction with pyridine-N-oxide. In all cases the carbene ligand stayed intact and the formation of Lewis acid/base pairs of the 2 VE ligand and (C2F5)3PF2 was never observed. As a result, mixtures of [(carbene)CuF] and (C2F5)3PF2 may serve as synthons for [(carbene)Cu]+, as demonstrated in this work.