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Query: EC:6.2.1.1 (
ACS
)
78,556
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Mitigation of the hydrogen evolution reaction (HER) is a key challenge in selective small molecule reduction catalysis. This is especially true of catalytic nitrogen (N
2
) and carbon dioxide (CO
2
) reduction reactions (N
2
RR and CO
2
RR, respectively) using H
+
/e
-
currency. Here we explore, via DFT calculations, three iron model systems, P
3
E
Fe (E = B, Si, C), known to mediate both N
2
RR and HER, but with different selectivity depending on the identity of the auxiliary ligand. It is suggested that the respective efficiencies of these systems for N
2
RR trend with the predicted N-H bonds strengths of two putative hydrazido intermediates of the proposed catalytic cycle, P
3
E
Fe(
NNH
2
)
+
and P
3
E
Fe(
NNH
2
). Further, a mechanism is presented for undesired HER consistent with DFT studies, and previously reported experimental data, for these systems; bimolecular proton-coupled-electron-transfer (PCET) from intermediates with weak N-H bonds is posited as an important source of H
2'
instead of more traditional scenarios that proceed via metal hydride intermediates and proton transfer/electron transfer (PT/ET) pathways. Wiberg bond indices provide additional insight into key factors related to the degree of stabilization of P
3
E
Fe(
NNH
2
) species, factors that trend with overall product selectivity.
ACS
Catal 2018 Feb 02
PMID:Fe-mediated HER vs N
2
RR: Exploring Factors that Contribute to Selectivity in P
3
E
Fe(N
2
) (E = B, Si, C) Catalyst Model Systems. 3055 33
