Valence-Inverted States of Nickel(II) Complexes Perform Facile C-H Bond Activation.

Valence-inverted reactivity (VIR) is discovered here through high-level computations of excited states of Ni(II) complexes that are generated by triplet energy transfer. For example, the so-generated 3 [(Ar)(bpy)Ni II (Br)] species possesses a valence-inverted occupancy, d xy 1 d xz 1 d x 2 -y 2 2 , wherein the uppermost d x 2 -y 2 orbital is metal-ligand antibonding. This state promotes C-H bond activation of THF and its cross-coupling to the aryl ligand. Thus, due to the metal-ligand antibonding character of d x 2 -y 2 , the d xy 1 d x 2 -y 2 2 subshell opens a Ni-coordination site by shifting the bidentate bipyridine ligand to monodentate plus a dangling pyridine. The tricoordinate Ni(II) intermediate inserts into a C-H bond of THF, transfers a proton to the dangling pyridine moiety, and eventually generates an arylated THF by reductive-coupling. The calculated high kinetic isotope effect is in accord with experiment, both revealing C-H activation. The VIR pattern is novel, its cross-coupling reaction is highly useful, and it is generally expected to occur in other d 8 complexes.