(513by) A Computational Approach to Systematic Ligand Design for C-H Bond Activation

Due to the need for C-H bond activation in methane to methanol (MTM) transformation ,we focus our attention to catalysts to assist in bond activation. Here we investigate this step using 3d and 4d transition metal oxides and show how systematic ligand design can transform them from inert compounds to efficient catalytic units. Computational studies utilizing density functional theory, multireference, and coupled cluster calculations have assisted in developing potential catalysts to selectively favor mechanisms with lower energy barriers with promising results.

In the case of niobium, the higher spin state facilitated the oxyl radical mechanism which has low energy barriers and thus has the ability to activate the second reaction step. The lower spin states on the other hand are endothermic with high energy barriers and facilitate the oxo 2+2 oxidation mechanism. For zirconium, we were able to stabilize the high spin excited state and make it the ground state of the system and found that weak field ligands such as chlorine stabilize the oxyl radical mechanism giving a reaction with lower energy barriers which compares favorably with our findings for niobium and iron.