Ruthenium Complexes of a Triphosphorus-Coordinating Pincer Ligand: Ru-P Ligand-Substituent Exchange Reactions Driven by Large Variations of Bond Energies.

The reaction of [(-cymene)RuCl] with the triphosphine ligand bis(2-di--butylphosphinophenyl)phosphine (PPP) results in an unusual exchange reaction in which a chloride ligand and a phosphorus-bound H atom are exchanged ("H-P/Ru-Cl exchange") to give the (chlorophosphine)ruthenium hydride complex (PPP)RuHCl [; PPP = bis(2-di--butylphosphinophenyl)chlorophosphine]. Density functional theory calculations indicate that the presumed initial product of metalation, (PPP)RuCl (), undergoes an H-P/Ru-Cl exchange via sequential P-to-Ru α-H migration to give the intermediate (PPP)RuHCl, followed by Ru-to-P α-Cl migration to give the observed product (crystallographically characterized). Dehydrochlorination of under a H atmosphere gives (PPP)RuH (), which then can undergo a second dehydrochlorination and addition of H to give (PPP)RuH ().

Reactivity of Iridium Complexes of a Triphosphorus-Pincer Ligand Based on a Secondary Phosphine. Catalytic Alkane Dehydrogenation and the Origin of Extremely High Activity.

The selective functionalization of alkanes and alkyl groups is a major goal of chemical catalysis. Toward this end, a bulky triphosphine with a central secondary phosphino group, bis(2-di--butyl-phosphinophenyl)phosphine (PPP), has been synthesized. When complexed to iridium, it adopts a meridional ("pincer") configuration.