Synthetic and Structural Studies of [AuCl₃(NHC)] Complexes

A series of N-heterocyclic carbene complexes [AuCl(NHC)] 1 [NHC: IPr, a; SIPr, b; IPrMe, c; IPrCl, d; IMes, e; SIMes, f; ItBu, g; IAd, h; and ICy, i] were reacted with chlorine gas or PhICl2 to afford [AuCl3(IPr)], 2a; [AuCl3(SIPr)], 2b; [AuCl3(IPrMe)], 2c; [AuCl3(IPrCl)], 2d; [AuCl3(IMes)], 2e; [AuCl3(SIMes)], 2f; [AuCl3(ItBu)], 2g; [AuCl3(IAd)], 2h; and [AuCl3(ICy)], 2i, respectively. Complete characterization by 1H and 13C NMR spectroscopies as well as by single-crystal X-ray diffraction was performed in order to discern electronic and structural differences between organogold(I/III) congeners. Calculations of the buried volume of the NHC ligand in complexes [AuCl3(NHC)] 2 were also performed in order to evaluate the steric hindrance of the NHC. These data permit comparisons with the related complexes [AuCl(NHC)] 1 and [AuBr3(NHC)].