Valence-Inverted States of Nickel(II) Complexes Perform Facile C–H Bond Activation
Shaohong Wang, Pengchen Ma, Sason Shaik, Hui Chen
Abstract
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)NiII(Br)] species possesses a valence-inverted occupancy, dxy1dxz1dx2–y22, wherein the uppermost dx2–y2 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 dx2–y2, the dxy1dx2–y22 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 d8 complexes.