Ammonia Synthesis by Hydrogenolysis of Titanium–Nitrogen Bonds Using Proton Coupled Electron Transfer

The
catalytic hydrogenolysis of the titanium–amide bond in (η5-C5Me4SiMe3)2­Ti­(Cl)­NH2 to yield free ammonia is described. The rhodium hydride,
(η5-C5Me5)­(py-Ph)­RhH
(py-Ph = 2-phenyl­pyridine), serves as the catalyst and promotes
N–H bond formation via hydrogen atom transfer. The N–H
bond dissociation free energies of ammonia ligands have also been
determined for titanocene and zirconocene complexes and reveal a stark
dependence on metal identity and oxidation state. In all cases, the
N–H BDFEs of coordinated NH3 decreases by >40
kcal/mol from the value in the free gas phase molecule.