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

A series of new Au­(I) hetero-bis-NHC complexes [Au­(iPr2-bimy)­(NHC)]­X (X = BF4, PF6, 2–6) and the hetero-tetrakis-NHC complex [Au2(iPr2-bimy)2(μ-ditz)]­(BF4)2 (7) have been synthesized using the Au­(I) acetato complex [Au­(O2CCH3)­(iPr2-bimy)] (C) as a basic metal precursor (iPr2-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene, ditz = 1,2,4-triazolidine-3,5-diylidene). The Au­(III) hetero-bis-NHC complex trans-[AuCl2(iPr2-bimy)­(Bn2-bimy)]­BF4 (12; Bn2-bimy = 1,3-dibenzylbenzimidazolin-2-ylidene) and the hetero-tetrakis-NHC complex all-trans-[Au2Cl4(iPr2-bimy)2(μ-ditz)]­(BF4)2 (13) were obtained by oxidation of their corresponding Au­(I) hetero-NHC precursors. For all Au­(I) hetero-NHC complexes, the 13C carbene signals of the constant iPr2-bimy ligand are found to be highly correlated with those in Pd­(II) analogues of the type trans-[PdBr2(iPr2-bimy)­(NHC)], which could be applied to detect the σ-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.