Treatment of [Fe
2(
-pdt)(CO)
6] [pdt = S(CH
2)
3S] with dppe(Ph
2PCH
2CH
2PPh
2) in refluxing toluene affords the asymmetriccomplex [Fe
2(
-pdt)(CO)
4(dppe)] (
1). Protonation of
1 with HBF
4-Et
2O in CH
2Cl
2 gives at room temperature the
-hydrido derivative[Fe
2(
-pdt)(CO)
4(dppe)(
-H)](BF
4) (
2). Monitoring the reaction by
1H,
31P, and
13C NMR at low temperature reveals unambiguouslythat the process of the protonation of
1 implies terminal hydrideintermediates.