A series of Au(I) and Au(III) mono-, homobis-, and heterobis(carbene) complexes, [AuCl(FPyr)] (2), [Au( i Pr2-bimy)2]PF6 (3), [Au(FPyr)2]PF6 (4), [Au(FPyr)( i Pr2-bimy)]PF6 (5), [AuCl3( i Pr2-bimy)] (6), [AuCl3(FPyr)] (7), [AuCl2( i Pr2-bimy)2]PF6 (8), [AuCl2(FPyr)2]PF6 (9), and [AuCl2(FPyr)( i Pr2-bimy)]PF6 (10), bearing the benzimidazole-derived i Pr2-bimy (1,3-diisopropylbenzimidazolin-2-ylidene) and/or the pyrazole-derived FPyr (1,2,3,4,6,7,8,9-octahydropyridazino[1,2-a]indazolin-11-ylidene) N-heterocyclic carbene (NHC) ligands have been synthesized. Complexes 2–10 have been fully characterized using multinuclei NMR spectroscopy, ESI mass spectrometry, and elemental analysis. X-ray diffraction analyses have been performed on 2, 3, 5, 6, and 8. Together with the previously reported [AuCl( i Pr2-bimy)] (1), the cytotoxic activities of all 10 complexes have been studied in vitro with the NCI-H1666 non-small cell lung cancer cell line. The cationic bis(carbene) complexes 3–5 and 8–10 show better cytotoxicity in comparison to cisplatin. In particular, the heterobis(carbene) complexes 5 and 10 have superior activity, with IC50 values of around 0.2 μM.

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 gold(I) NHC complex bearing a heteroalicyclic indazolin-3-ylidene ligand, [AuCl(Indy)] (1) (Indy = 6,7,8,9-tetrahydropyridazino[1,2-a]indazolin-3-ylidene), has been synthesized via the silver–carbene transfer method. Conversion of complex 1 to its heavier halido analogues [AuBr(Indy)] (2) and [AuI(Indy)] (3) was achieved by metathesis reactions involving LiBr and NaI in acetone, respectively. In contrast to 1 and 2, complex 3 undergoes ligand disproportionation/autoionization upon crystallization, forming the solid complex salts [Au3I2(Indy)4][Au3I4(Indy)2] (3′) or [Au(Indy)2][AuI2] (3″) depending on the solvent used. This reversible process assisted by aurophilic interactions, and only occurring in the iodido complex 3, has been studied further by spectroscopic comparison with [Au(Indy)2]BF4 (4) and selective conversion of 3 to the gold(III) species [AuI3(Indy)] (5). All complexes 1–5 have been fully characterized using multinuclei NMR spectroscopies, ESI mass spectrometry, and X-ray diffraction analysis.

A series of cationic gold(I) heteroleptic complexes bearing the pyrazole-derived N-heterocyclic carbene (NHC) FPyr (1,2,3,4,6,7,8,9-octahydropyridazino[1,2-a]indazolin-11-ylidene), and either a 1,3-disubstituted benzimidazole-derived NHC of the type RR'-bimy (3: R = R' = CHPh2; 4: R = CHPh2, R' = (i)Pr; 5: R = R' = CH2Ph; 6: R = R' = (i)Bu; 7: R = R' = n-Pr; 8: R = R' = Et; 9: R = R' = 2-propenyl) or a non-NHC co-ligand L (10: L = PPh3; 11: L = P(OPh)3; 12: L = DMAP) (DMAP = 4-dimethylaminopyridine) have been synthesized from [AuCl(FPyr)] (1). Complexes 3-12 have been characterized using multinuclei NMR spectroscopies, ESI mass spectrometry, and elemental analysis. X-ray diffraction analyses have been performed on complexes 5, 6, and 9-11. To the best of our knowledge, 11 represents the first gold-NHC complex to bear the P(OPh)3 ligand. The cytotoxic activities of complexes 3-12 have been studied in vitro with the NCI-H1666 non-small cell lung cancer cell line.

We report the profiling of the metabolic stability, normal cell inhibition, and genotoxicity of the two gold complexes [Au (iPr2‐bimy)2]PF6 (1) and [Au (Fpyr)(iPr2‐bimy)]PF6 (2), which show strong apoptotic activities in lung cancer cells. Liver microsomal tests revealed that the compounds have a relatively high half‐life compared to midazolam and do not suffer rapid metabolism and in vitro clearance. The cytotoxic potential of these compounds were also relatively weak in normal cells, with higher IC50 values compared to cancer cells, with a 2–60 times difference. The Ames test revealed that the compounds do not give rise to any mutations as well. Overall, the compounds showed stability in liver microsomes, specificity for cancer cells, and a lack of genotoxic potential.