Open AccessThe Mechanism of N–N Double Bond Cleavage by an Iron(II) Hydride Complex
Author(s) -
Sarina M. Bellows,
Nicholas A. Arnet,
Prabhuodeyara M. Gurubasavaraj,
William W. Brennessel,
Eckhard Bill,
Thomas R. Cundari,
Patrick L. Holland
Publication year - 2016
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.6b04654
Subject(s) - chemistry , hydride , reductive elimination , photochemistry , bond cleavage , redox , kinetic isotope effect , cleave , azobenzene , dimer , metal , medicinal chemistry , inorganic chemistry , molecule , catalysis , organic chemistry , enzyme , deuterium , physics , quantum mechanics
The use of hydride species for substrate reductions avoids strong reductants, and may enable nitrogenase to reduce multiple bonds without unreasonably low redox potentials. In this work, we explore the N═N bond cleaving ability of a high-spin iron(II) hydride dimer with concomitant release of H2. Specifically, this diiron(II) complex reacts with azobenzene (PhN═NPh) to perform a four-electron reduction, where two electrons come from H2 reductive elimination and the other two come from iron oxidation. The rate law of the H2 releasing reaction indicates that diazene binding occurs prior to H2 elimination, and the negative entropy of activation and inverse kinetic isotope effect indicate that H-H bond formation is the rate-limiting step. Thus, substrate binding causes reductive elimination of H2 that formally reduces the metals, and the metals use the additional two electrons to cleave the N-N multiple bond.