Cationic gold(I) heteroleptic complexes bearing a pyrazole-derived N-heterocyclic carbene: syntheses, characterizations, and cytotoxic activities

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' = Pr-i; 5: R = R' = CH2Ph; 6: R = R' = Bu-i; 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.