Cationic silyldiazenido complexes of the Fe(diphosphine)₂(N₂) platform: structural and electronic models for an elusive first intermediate in N₂ fixation

Abstract

The first cationic Fe silyldiazenido complexes, [Fe(PP)2(NN–SiMe3)]+[BArF4]− (PP = dmpe/depe), have been synthesised and thoroughly characterised. Computational studies show the compounds to be useful structural and electronic surrogates for the more elusive [Fe(PP)2(NN–H)]+, which are postulated intermediates in the H+/e− mediated fixation of N2 by Fe(PP)2(N2) species

Reactivity and Structure of Complexes of Small Molecules: Dinitrogen

“…Comprehensive Coordination Chemistry Authors N. Mézailles / N 2 page 89 derivative of Fe, showing an acute NNSi bond angle of ca 130°. 267 DFT calculations were carried out and confirm a significant FeN π interaction as well as population of a NN π* orbital, consistent with the observed ν NN stretches at 1732 and 1727 cm -1 (depe and dmpe complexes respectively). In 2017, Szymczak showed that an increase in the NN bond polarization could favor protonation at N rather than at Fe.…”

Enhanced Activation of Coordinated Dinitrogen with p‐Block Lewis Acids

“…Beyond validating the “push–pull hypothesis”, characterization of such mono‐protonated species offers a snapshot of what may resemble elusive FeN 2 H intermediates in catalytic N 2 reductions . Ashley and co‐workers cleverly made use of the more Lewis acidic Me 3 Si + silylium ion as a proton mimic to characterize the first cationic silyldiazenido iron complexes (Scheme ) . Treatment of 5 or [Fe(dmpe) 2 (N 2 )] ( 8 , dmpe=1,2‐bis(dimethylphosphino)ethane) with Me 3 SiCl/KBAr F 4 afforded the ionic compounds 9 and 10 bearing a bent NNSi arrangement [Ar F =3,5‐(CF 3 ) 2 C 6 H 3 ].…”

“…[3b, 17] Ashley and co-workers cleverlym ade use of the more Lewis acidic Me 3 Si + silyliumi on as ap rotonm imic to characterize the first cationic silyldiazenido iron complexes (Scheme 4). [18] Treatment of 5 or [Fe(dmpe) 2 (N 2 )] (8,d mpe = 1,2-bis(dimethylphosphino)ethane) with Me 3 SiCl/KBAr F 4 afforded the ionic compounds 9 and 10 bearing ab entN NSi arrangement[Ar F = 3,5-(CF 3 ) 2 C 6 H 3 ]. IR data were in line with an otable weakening of the NÀNb ond.…”

Synthesis, Characterization, and Comparative Theoretical Investigation of Dinitrogen-Bridged Group 6-Gold Heterobimetallic Complexes

“… 45 The N–N–Au angle of 142.6° suggests a similar bonding situation as the one found in main group adducts of end-on dinitrogen complexes. 11e , 12 , 46 …”