Molecular orbital studies of titanium nitride chemical vapor deposition: gas phase β-elimination

Chemical vapor deposition (CVD) of titanium nitride can be carried out using Ti(NR2)4 and NH3 (R=Me or Et). Imido compounds are thought to be key intermediates in this process. Formation of Ti(NR2)2NH from Ti(NR2)4 can proceed by ligand exchange with NH3 followed by elimination of NHR2. When R=Et there is an alternate β-elimination pathway that also leads to imido formation. At the B3LYP/6-311G(d) level of theory, this pathway has a barrier of 51.1 kcal/mol and the reaction is endothermic by 68.0 kcal/mol. By comparison, ligand exchange has a barrier of 35.5 kcal/mol, suggesting that β-elimination does not contribute significantly to Ti(NR2)2NH formation.