A series of new Au­(I) hetero-bis-NHC complexes [Au­( i Pr2-bimy)­(NHC)]­X (X = BF4, PF6, 2–6) and the hetero-tetrakis-NHC complex [Au2( i Pr2-bimy)2(μ-ditz)]­(BF4)2 (7) have been synthesized using the Au­(I) acetato complex [Au­(O2CCH3)­( i Pr2-bimy)] (C) as a basic metal precursor ( i Pr2-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene, ditz = 1,2,4-triazolidine-3,5-diylidene). The Au­(III) hetero-bis-NHC complex trans-[AuCl2( i Pr2-bimy)­(Bn2-bimy)]­BF4 (12; Bn2-bimy = 1,3-dibenzylbenzimidazolin-2-ylidene) and the hetero-tetrakis-NHC complex all-trans-[Au2Cl4( i Pr2-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 i Pr2-bimy ligand are found to be highly correlated with those in Pd­(II) analogues of the type trans-[PdBr2( i Pr2-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.

A complete series of ten Au(I) and Au(III) NHC complexes of the general formulas [Au I X( i Pr 2 -bimy)] (1−3, X = Cl, Br, and I), [Au I ( i Pr 2 -bimy) 2 ]BF 4 (4), [Au III X 3 ( i Pr 2 -bimy)] (5−7, X = Cl, Br, and I) and trans-[Au III X 2 ( i Pr 2 -bimy)]BF 4 (8−10, X = Cl, Br, and I) bearing the i Pr 2 -bimy ligand, and all three common halido ligands have been synthesized and fully characterized. Detailed trends in their NMR and UV−Vis spectroscopic properties have been studied, and their electrochemical behavior have been probed by cyclic voltammetry. The solid state molecular structures of all new complexes determined by single crystal X-ray diffraction are also described.

A series of 2-coordinate heteroleptic Cu(I) complexes of the general formula [Cu­(IPr)­(L)]­PF6 (2–5, L = NHC or phosphine) have been synthesized via either (i) chlorido substitution by phosphine or in situ generated free NHC or (ii) the Ag–NHC transfer protocol using [CuCl­(IPr)] (1) as a precursor (IPr = 1,3-bis­(2,6-diiso­propyl­phenyl)­imidazolin-2-ylidene). The reactions of precursor 1 with diphosphine ligands afforded 3-coordinate heteroleptic Cu(I) complexes of the type [Cu­(IPr)­(L2)]­PF6 (6 and 7, L2 = diphosphine). Complexes 1–7 have been subjected to a catalytic one-pot sequential CuAAC study, in which aromatic amines serve as the precursors to aryl azides. Hetero-bis(NHC) complexes 2–4 proved to be generally superior compared to their mixed NHC/phosphine counterparts 5–7. Overall, complex [Cu­(Bn2-imy)­(IPr)]­PF6 (2), bearing the Bn2-imy (Bn2-imy = 1,3-dibenzyl-imidazolin-2-ylidene) coligand, showed the best catalytic performance.

A series of NHC-containing [C^N]- or [C^C']-type palladacyclic complexes of the general formula [PdBr(iPr2-bimy)(L^X)] (5-8, 11, 12, iPr2-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) have been synthesized and fully characterized. Using these complexes, the donating abilities of monoanionic chelators were probed for the first time. The [C^N]-type palladacycles 5-8 were prepared from acetato-bridged dipalladium complexes [Pd(μ-CH3COO)(C^N)]2 (1-4) and iPr2-bimy·H+Br-as precursors. In the case of the [C^C']-type NHC palladacycles (11, 12), the hetero-bis(NHC) complexes trans-[PdBr2(iPr2-bimy)(trz)] (8, 9, trz = 1,2,3-triazolin-5-ylidene) containing the iPr2-bimy probe were first prepared followed by acetate-assisted cyclopalladations. The 13Ccarbene NMR signals of the iPr2-bimy ligands in all complexes (i.e. HEP and HEP2 values) are found to rationally reflect the donating abilities of the incorporated trz or [L^X]-type chelators with the exception of the Bzpy ligand (Bzpy = 2-(2-pyridinylmethyl)phenyl-C,N). This has been attributed to its larger bite angle, the resulting varied coordination geometry and the lack of electronic delocalization between the two donor units. The donicities of [L^X]-type chelators studied in this work were found to surpass those of all other bidentate ligands evaluated by HEP2 thus far.