Dinitrogen Binding and Functionalization in Low-Coordinate Alkynyliron Complexes

Alkynyl complexes of low-coordinate transition metals offer a sterically open environment and unusual bonding for reactivity. Here, we explore the capacity of iron(I) alkynyl complexes to bind N2, and isolate an N2 complex including its X-ray crystal structure. Silylation of this complex gives a formally iron(IV) complex with a disilylhydrazido(2–) ligand, but NBO analysis indicates that an iron(II) formulation is more accurate. The structure of this compound is similar to an earlier reported phenyl complex in which phenyl migration forms a new N–C bond, but the alkynyl group does not migrate. DFT calculations are used to test the possible reasons, and the most likely is the stronger Fe–C bond energy in the alkynyl complex.