Fe-Catalyzed Conversion of N2to N(SiMe3)3via an Fe-Hydrazido Resting State

The catalytic conversion of N 2 o N(SiMe 3 ) 3 by homogeneous transition metal compounds is a rapidly developing field, yet few mechanistic details have been experimentally elucidated for 3 d element catalysts. Herein we show that Fe(PP) 2 (N 2 ) (PP = R 2 PCH 2 CH 2 PR 2 ; R = Me, 1 Me ; R = Et, 1 E ) are highly effective for the catalytic production of N(SiMe 3 ) 3 from N 2 (using KC 8 /Me 3 SiCl), with the yields being the highest reported to date for Fe-based catalysts. We propose that N 2 fixation proceeds via electrophilic N β silylation and 1e - reduction to form unstable Fe I (NN-SiMe 3 ) intermediates, which disproportionate to 1 Me/E and hydrazido Fe II [N-N(SiMe 3 ) 2 ] species (3 Me/E ); the latter act as resting states on the catalytic cycle. Subsequent 2e - reduction of 3 Me/E leads to N-N scission and formation of [N(SiMe 3 ) 2 ] - and putative anionic Fe imido products. These mechanistic results are supported by both experiment and DFT calculations.