A novel unsymmetrically disubstituted propanedithiolate compound [Fe2(CO)4(κ2-dmpe)(μ-pdt)] (1) (pdt = SCH2CH2CH2S, dmpe = Me2PCH2CH2PMe2) was synthesized by treatment of [Fe2(CO)6(μ-pdt)] with dmpe in refluxing THF. Compound 1 was characterized by single-crystal X-ray diffraction analysis. Protonation of 1 with HBF4·Et2O in CH2Cl2 gave at room temperature the μ-hydrido derivative [Fe2(CO)4(κ2-dmpe)(μ-pdt)(μ-H)](BF4)] (2). At low temperature, 1H and 31P–{1H} NMR monitoring revealed the formation of a terminal hydride intermediate 3. Comparison of these results with those of a VT NMR study of the protonation of symmetrical compounds [Fe2(CO)4L2(μ-pdt)] [L = PMe3, P(OMe)3] suggests that in disubstituted bimetallic complexes [Fe2(CO)4L2(μ-pdt)], dissymmetry of the complex is required to observe terminal hydride species. Attempts to extend the series of chelate compounds [Fe2(CO)4(κ2-L2)(μ-pdt)] by using arphos (arphos = Ph2AsCH2CH2PPh2) were unsuccessful. Only mono- and disubstituted derivatives [Fe2(CO)6−n(Ph2AsCH2CH2PPh2)n(μ-pdt)] (n = 1, 4a; n = 2, 4b), featuring dangling arphos, were isolated under the same reaction conditions of formation of 1. Compound 4b was structurally characterized.