The N-heterocyclic carbene (NHC) precursors 1-[(E)-2-butenyl]-3-(4-ferrocenylphenyl)imidazolium bromide (2) and 1-[(E)-2-butenyl]-3-(4-ferrocenylphenyl)imidazolium tetrafluoroborate (3) were derived from 1-(4-ferrocenylphenyl)imidazole. Ferrocenyl complex 3 reacts with Ag₂O and chloro(dimethylsulfide)gold(I) in the presence of tetraethylammonium chloride to produce the mixed metal species bis{1-[(E)-2-butenyl]-3-(4-ferrocenylphenyl)-2H-imidazol-2-ylidene}gold(I) tetrafluoroborate (4). Single crystal X-ray structure analyses of 1, 3 and 4 indicate that the NCHN-hydrogen in 3 is hydrogen bonded to the BF₄ ⁻ anion [C(H1)⋯F, 3.265(4) Å], as is also reflected in the position of its ¹H NMR chemical shift. Cytotoxicity studies show that complex 4 is selective for cancer cells and active against the tumour cell lines Jurkat and MCF 7.