Gold and Palladium Hetero-Bis-NHC Complexes: Characterizations, Correlations, and Ligand Redistributions

A series of new Au(I) hetero-bis-NHC complexes [Au(Pr-i(2)-bimy)(NHC)]X (X = BF4, PF6, 2-6) and the hetero-tetrakis-NHC complex [Au-2(Pr-i(2)-bimy)(2)(mu-ditz)](BF4)(2) (7) have been synthesized using the Au(I) acetato complex [Au(O2CCH3)(Pr-i(2)-bimy)] (C) as a basic metal precursor (Pr-i(2)-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene, ditz = 1,2,4-triazolidine-3,5-diylidene). The Au(III) hetero-bis-NHC complex trans-[AuCl2(Pr-i(2)-bimy)(Bn-2-bimy)]BF4 (12; Bn-2-bimy = 1,3-dibenzylbenzimidazolin-2-ylidene) and the hetero-tetrakis-NHC complex all-trans-[Au2Cl4(Pr-i(2)-bimy)(2)(mu-ditz)](BF4)(2) (13) were obtained by oxidation of their corresponding Au(I) hetero-NHC precursors. For all Au(I) hetero-NHC complexes, the C-13 carbene signals of the constant Pr-i(2)-bimy ligand are found to be highly correlated with those in Pd(II) analogues of the type trans-[PdBr2(Pr-i(2)-bimy)(NHC)], which could be applied to detect the sigma-donating ability of the trans standing NHC. In addition, an interesting ligand redistribution process was observed for some of the Au(I) hetero-bis-NHC Complexes.