A Coordination Strategy to Realize a Sextuply Bonded Complex
Synthesis of higher-order multiple bond 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 temperature. Here, we propose a strategy to construct a sextuple bond in a dinuclear transition metal complex based on the 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 electron configuration. Calculated large formation energies of these complexes indicate the large possibility of the synthesis. Electronic structure and sextuply bonding interactions are analyzed in detail.