Investigation on the protonation of a trisubstituted [Fe(2)(CO)(3)(PPh(3))(kappa(2)-phen)(mu-pdt)] complex: rotated versus unrotated intermediate pathways.

The substitution of PPh(3) for a carbonyl group at the {Fe(CO)(3)} moiety in [Fe(2)(CO)(4)(kappa(2)-phen)(mu-pdt)] results in the formation of the trisubstituted complex [Fe(2)(CO)(3)(PPh(3))(kappa(2)-phen)(mu-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 [Fe(2)(CO)(3)(L)(kappa(2)-phen)(mu-pdt)] (L = PPh(3), 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.