Evidence for the formation of terminal hydrides by protonation of an asymmetric iron hydrogenase active site mimic

Treatment of [Fe-2(mu-pdt)(CO)(6)] [pdt = S(CH2)(3)S] with dppe (Ph2PCH2CH2PPh2) in refluxing toluene affords the asymmetric complex [Fe-2(mu-pdt)(CO)(4)(dppe)] (1). Protonation of 1 with HBF4-Et2O in CH2Cl2 gives at room temperature the mu-hydrido derivative [Fe-2(mu-pdt)(CO)(4)(dppe)(mu-H)](BF4) (2). Monitoring the reaction by H-1, P-31, and C-13 NMR at low temperature reveals unambiguously that the process of the protonation of 1 implies terminal hydride intermediates.