The Haber-Bosch Process is an important industrial process employed for the synthesis of ammonia (NH₃) from atmospheric nitrogen (N₂). However, due to the chemical inertness of gaseous N₂, the process requires drastic conditions and accounts for about 2% of the global energy consumption. The process is vital for human sustenance since ammonia is used for the manufacture of fertilizers and significant feedstock-chemicals for the polymer industry. Cheap and sustainable production of ammonia is also important because of its potential as a carbon-independent alternate fuel. Therefore, the development of sustainable, first-row transition metal catalysts for N₂ reduction under mild conditions and efficient ammonia oxidation is of critical importance.

M(IV)/Co(-I) systems with three bridging phosphinoamide ligands, where M(IV) are group 4 metal centers, have been shown to support end-on dinitrogen binding. The nitrogen is bound to the Co(-I) center in these complexes and spectroscopic data suggests a partially activated N–N bond. Furthermore, Zr/Co systems with (mono) and (bis)phosphinoamide bridges have been shown to be more reactive than the (tris)phosphinoamide analogues. Therefore, the M/Co (M = Zr, Hf) heterobimetallic complexes with two bridging phosphinoamide ligands were synthesized, characterized, and their potential to activate molecular nitrogen was examined. A [Zr₂Co₂]-tetrametallic complex with N₂ in an unusual κ^{<span style="font-size:10.8333px">1</span>}:η²:η²:κ¹ binding mode was also isolated and characterized. The N₂-bound complex was found to catalyze N₂-reduction and in the presence of trimethylsilyl chloride formed tris(trimethylsilyl) amine. These investigations will be presented in this talk.

Joshua Shoopman

Graduate Research Associate, The Ohio State University

Appearances