Mechanistic insight into N=N cleavage by a low-coordinate iron(II) hydride complex.
The reaction pathways of high-spin iron hydride complexes are relevant to the mechanism of N2 reduction by nitrogenase, which has been postulated to involve paramagnetic iron-hydride species. However, almost all known iron hydrides are low-spin, diamagnetic Fe(II) compounds. We have demonstrated that the first high-spin iron hydride complex, LtBuFeH (LtBu = bulky beta-diketiminate), reacts with PhN=NPh to completely cleave the N-N double bond, giving LtBuFeNHPh. Here, we disclose a series of experiments that elucidate the mechanism of this reaction. Crossover and kinetic experiments rule out common nonradical mechanisms, and support a radical chain mechanism mediated by iron(I) species including a rare eta2-azobenzene complex. Therefore, this high-spin iron(II) hydride can break N-N bonds through both nonradical and radical insertion mechanisms, a special feature that enables novel reactivity.
Sadique
Azwana R
AR
Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.
Gregory
Elizabeth A
EA
Brennessel
William W
WW
Holland
Patrick L
PL
D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D009591:Nitrogenase / Q000737:chemistry / Q000378:metabolism
D007501:Iron; D009591:Nitrogenase; D009584:Nitrogen