Theoretical study of FMO adjusted C-H cleavage and oxidative addition in nickel catalysed C-H arylation

Nickel catalysis has recently emerged as an important addition to the suite of transition metal-catalysed C-H bond functionalization methods. Here we report density functional theory calculations to elucidate the mechanism of Ni(II)-catalysed C–H arylation with a diaryliodonium salt or a phenyliodide. The effect of the choice of oxidant on the order of oxidative addition and C–H bond cleavage is investigated. When the active catalyst is oxidized by the diaryliodonium salt oxidant, C–H bond cleavage occurs to give an alkyl-aryl-Ni(IV) species. Conversely, the relatively weak oxidant phenyliodide leads to an alternative reaction sequence. The active catalyst first undergoes C–H bond cleavage, followed by oxidative addition of the phenyliodide to give a Ni(IV) species. Frontier molecular orbital analysis demonstrates that the reaction sequence of oxidative addition and C–H bond cleavage is determined by the unoccupied Caryl–I bond antibonding orbital level of the oxidant. Nickel-catalysed C-H functionalisation reactions are of increasing importance. Here the mechanism of Ni(II)-catalysed C-H arylation of amides is shown to depend on the nature of the oxidant and in particular the energy of its Caryl-I antibonding orbital.