Low-Coordinate Iron Hydride Chemistry at an N,N,C-Heteroscorpionate Platform

Locally high-spin iron hydrides are proposed to play a critical role as intermediates in iron–molybdenum cofactor (FeMoco)-catalyzed N2 fixation. Inspired by these biological systems, we report herein our initial investigations into low-coordinate iron hydride chemistry supported by our N,N,C-heteroscorpionate ligands. Those ligands with smaller steric profiles are unable to completely suppress the formation of a binuclear [Fe(μ2-H)]2 complex; however, the incorporation of more substantial steric bulk allows for the isolation of a rare example of a terminal, high-spin (S = 2) Fe2+ hydride. Fourier transform infrared spectroscopy suggests an unusually weak Fe–H bond in the latter molecule. Mössbauer spectroscopies, coupled with density functional theory calculations, highlights the substantial influence of the terminal hydride ligand on 57Fe isomer shift.