Dinitrogen Binding and Functionalization in Low-Coordinate Alkynyliron Complexes

Abstract

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.

Dinitrogen Binding and Functionalization from a Low-Coordinate Alkynyliron Complex

“… − Inspired by recent findings from our group showing that reduced, three-coordinate iron­(I) aryl complexes can bind and functionalize N 2 through a silylation-migration pathway (Scheme ), − we sought to explore the analogous reactivity with alkynyl complexes. Here, we report the synthesis and reactivity of monoalkynyliron complexes supported by a β-diketiminate ligand, including the binding of N 2 at an iron­(I) alkynyl complex and the isolation of a formally iron­(IV) alkynyl species …”

“…Here, we report the synthesis and reactivity of monoalkynyliron complexes supported by a β-diketiminate ligand, including the binding of N 2 at an iron(I) alkynyl complex and the isolation of a formally iron(IV) alkynyl species. 45 ■ RESULTS AND DISCUSSION New Alkynyliron(II) Complex. Three-coordinate iron(II) alkynyl complexes have been reported using a larger βdiketiminate ligand having tert-butyl groups on the back- bone.…”