Investigation on the Protonation of a Trisubstituted [Fe₂(CO)₃(PPh₃)(κ²-phen)(μ-pdt)] Complex: Rotated versus Unrotated Intermediate Pathways

The substitution of PPh3 for a carbonyl group at the {Fe(CO)3} moiety in [Fe2(CO)4(κ2-phen)(μ-pdt)] results in the formation of the trisubstituted complex [Fe2(CO)3(PPh3)(κ2-phen)(μ-pdt)] (2). Unlike its tetracarbonyl precursor, the protonation of 2 at low temperature does not afford any apparent transient terminal hydride species. Hydride formation for [Fe2(CO)3(L)(κ2-phen)(μ-pdt)] (L = PPh3, CO) species is also studied by density functional theory calculations, which show that activation barriers to give terminal and bridging hydrides can be remarkably close for this class of organometallic compounds.