The contribution of metal identity to the activation and functionalization of methane by a series of three-coordinate imide complexes is evaluated in silico for a 3-by-3 block of metals from Fe to Pt. Three mechanisms were studied: oxidative addition (OA) to the metal; hydrogen atom abstraction (HAA) by the imide nitrogen; and, 2+2 addition across the metal-imide bond. In no studied case, was a 2+2 mechanism preferred, perhaps suggesting this mechanism is largely (entirely?) the domain of d0 imides. There is a diagonal relationship within the nonet of metals studied in that OA is preferred for earlier, heavier (5d) members of the series, transitioning to an HAA mechanism for later, lighter (3d) imides. DFT indicates that important parameters in partitioning between HAA and OA mechanisms include the strength of the metal-imide π-bond, the ability of larger metals to accommodate increases in formal oxidation state and coordination number, and the soft acid/base compatibility of larger transition metals with soft hydride and methyl ligands.

DFT survey of the effects of d-electron count and metal identity on the activation and functionalization of C−H bonds for mid to late transition metals

2019 Spring National Meeting

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