DFT study of electrostatic effects upon methane activation by early, high-valent multiply bonded complexes

Abstract

The research presented here focuses on the electrostatic effect of varying alkali metal cations (Li+ through Cs+) in the outer coordination sphere of model methane activating complexes with metal-nitrogen multiple bonds. Lighter metal alkali metal cations yield reduced methane activation barriers (ΔG‡), with the lowest barrier computed for the Li+ salt; moreover, all modeled salts have lower ΔG‡ than the corresponding anion in polar solvents. Via variation of the polarity of continuum solvents, this research also indicates that electrostatic effects are likely to be manifested most significantly in the low polarity, hydrophobic solvents typically used for inorganic and organometallic complexes capable of methane activation. Taken together, the results of these DFT simulations suggest that electrostatic effects have the potential to significantly decrease methane activation barriers.