Reduction of Dinitrogen via 2,3'-Bipyridine-Mediated Tetraboration.

A new molecular system for nitrogen reduction, involving a 2,3'-bipyridine-anchored, end-on-bridging dinitrogen complex of the Me2B-BMe2 intermediate (4), has been explored by theoretical methods. The 2,3'-bipyridine-mediated cleavage of the Bsp3-Bsp3 bond in 4 may lead to transient electron-rich sp3-hybridized boron species and subsequent activation of the strong N≡N triple bond of the complexed N2. Through a boryl transfer sequence, a catalytic cycle may be achieved for the reductive addition of diboranes to a dinitrogen molecule with an energy span of 23 kcal/mol. In addition, the reaction is exothermic by 80.5 kcal/mol, providing a substantive chemical driving force.