Irradiation of Cp(CO) 2Fe[C(SCH 3) 2] + in CH 3CN solution with UV light produces high yields of Cp(CO)(CH 3CN)Fe[C(SCH 3) 2] +; the reaction appears to be general for other Cp(CO) 2Fe[carbene] + complexes. The CH 3CN ligand of Cp(CO)(CH 3CN)Fe[C(SCH 3) 2] + is readily displaced by other ligands to form Cp(CO)(L)Fe[C(SCH 3) 2] + (L = P(OPh) 3, P(OCH 3) 3, PPh 3, AsPh 3, SbPh 3, CH 3NC, C 5H 5N) in good yields. Carbon-13 NMR studies of the Cp(CO)(L)Fe[C(SCH 3) 2] + complexes show a general downfield shift of the C(carbene) Resonance as Fe→C(carbene) π-backbonding is increased by changes in L. Temperature dependent 1H NMR studies of the SC(carbene) rotational barrier indicate that S→C(carbene) π-donation decreases as Fe→C(carbene) π-backbonding is increased by changing L. The reactivity of these complexes towards primary and secondary amines to form Cp(CO)(L)Fe(CNR) + and Cp(CO)(L)Fe[C(SCH 3)NR 2] + derivatives also decreases as Fe→C(carbene) π-backbonding is increased by varying L.