Studies of the protonation of [Fe-2(CO)(4)(kappa(2)-PNP)(mu-pdt)] (1; PNP = (Ph2PCH2)(2)NCH3) by HBF4 center dot Et2O showed that the nature of the reaction product depends on whether the reaction is conducted in acetone or in dichloromethane. In acetone, an N-protonated form, 2, is isolated. Tautomerization of 2 in CH2Cl2 gives rise to a mu-hydride species 3. Variable-temperature NMR experiments have been performed to clarify the processes involved.