Catalytic Dinitrogen Conversion to Secondary Silylamines using Bimetallic Titanium Aryloxides

A tetraphenolate-supported bimetallic Ti complex undergoes multiple two-electron reductions, the last of which leads to the reductive activation of dinitrogen. The inclusion of weak acid and silyl electrophiles during the reduction enables the catalytic conversion of N2 to purely secondary amines. Yields of up to 35.9 equivalents of amine per complex are produced under ambient conditions. The Zr analogue is also a competent catalyst. A detailed electron paramagnetic resonance (EPR) spectroscopic, crystallographic, and computational analysis of the reduced intermediates, and comparisons with the Zr analogues, helps explain the roles of the Group 4 metal, reductant, and ligand.