By using 3,7‐dithianonane‐1,9‐dithiol (S4) and N,N′‐dimethyl‐N,N′‐bis(2‐mercaptoethyl)ethylenediamine (N2S2) as ligands, two CH3CN‐coordinated nickel‐iron heterodimetallic complexes, [NiS4Fe(CH3CN)Cp*][PF6] (1a) and [NiN2S2Fe(CH3CN)Cp*][PF6] (1b) (Cp* = η5‐C5Me5), were synthesized and characterized spectroscopically and crystallographically. Reactivities of 1a and 1b towards CO, CH2Cl2, HBF4, and NOPF6 have also been investigated. A series of complexes coordinated with small molecules [NiS4Fe(L)Cp*][PF6]n [n = 1, L = Cl (2a), CO (3a); n = 2, L = NO (4a)], [NiN2S2Fe(L)Cp*][PF6] [L = Cl (2b), CO (3b)] were obtained. We also studied the redox properties of 2a, 2b, 3a, and 3b by cyclic voltammetry in CH2Cl2 and in CH3CN solution. Complex 3a was found to be an excellent electrocatalyst for proton reduction from HBF4.