Reaction of Fe-2(mu-S2C3H6)(CO)(6) (1) with 2 equiv of t-BuNC affords a disubstitued species Fe-2(mu-S2C3H6)(CN-t-Bu)(2)(CO)(4) (2). The structure of 2 has been determined by X-ray crystallography, which shows that in the solid state both isonitrile ligands are cis to sulfur. In solution, NMR and IR spectroscopy suggest that multiple isomers are present. Protonation of 2 occurs at the Fe-Fe bond to give a cationic complex 3 as four different isomeric species. Complex 3 does not react with deuterium gas (98 psi) in the absence of light. Irradiation of solutions of 3 with visible light under D-2 gas leads to formation of HD.