High valent iron nitrides
Prof. Jeremy M. Smith
Department of Chemistry and Biochemistry
New Mexico State University
Four-coordinate tris(carbene)borate iron(IV) nitrido complexes PhB(RIm)3Fe≡N (R =
t
Bu, Mes) are highly reactive towards nitrogen atom transfer. Two-electron reduction of
the nitrido complexes is effected by a range of nucleophiles, with complete nitrogen atom
transfer occurring in some instances. Mechanistic investigations of the reaction with
triarylphosphines, supported by electronic structure calculations, suggest a dual nature
transition state for nitrogen atom transfer. High yields of ammonia are formed from the
reaction of PhB(MesIm)3Fe≡N with hydrogen atom donors. Formation of the first N-H
bond is proposed to occur by a one-electron hydrogen atom transfer reaction. Oxidation
of PhB(tBuIm)3Fe≡N allows for the first structural characterization of a bona-fide iron(V)
complex.