A coordination strategy to realize a sextuply-bonded complex

Abstract

The synthesis of higher-order multiple bonds is a great challenge in chemistry. However, no stable compound with a sextuple bond has been reported, except for Mo₂ in an inert matrix at low temperatures. Herein, we propose a strategy to construct a sextuple bond in a dinuclear transition metal complex based on complete active space second-order perturbation theory (CASPT2) and density functional theory calculations. When the dinuclear core M₂ (M = W, Mo, and Re⁺) is capped by two neutral electron-donating ligands at both M–M ends, a sextuple bond can be realized. The proposed ligands stabilize the M₂ core by the coordination, conserve the six bonding orbitals in the occupied space, and suppress the weight of the δ–δ* excited electronic configuration. Calculated large formation energies of these complexes indicate the large possibility of the synthesis. Electronic structures and sextuply bonding interactions were analyzed in detail.