Exploring secondary-sphere interactions in Fe–N_xH_ycomplexes relevant to N₂fixation

Abstract

Pendant amines on a scaffold for Fe–N2 chemistry form hydrogen bonds with NxHy substrates and facilitate proton delivery to Fe.

Positional effects of second-sphere amide pendants on electrochemical CO2 reduction catalyzed by iron porphyrins

“… 42 – 45 Second-sphere donors have also been shown to play important roles in structural mimics of alcohol dehydrogenase, 46 , 47 as well as in complexes for stoichiometric reduction of nitrite, 48 , 49 nitrate, 50 and nitrogen. 51 Furthermore, second-sphere pendants have been incorporated into electrocatalyst scaffolds to facilitate protonation steps relevant to H 2 evolution 52 – 54 and O 2 reduction, 55 , 56 and to stabilize adducts or promote C–O bond cleavage in CO 2 reduction. 11 , 12 , 57 – 59 With specific regard to CO 2 reduction, elegant work on iron tetraphenylporphyrins by Savéant, Costentin, and Robert has explored the use of phenol-based pendants for enhancing electrochemical CO 2 reduction.…”

Selectivity of tungsten mediated dinitrogen splitting vs. proton reduction

“…8,9 Attempts to stabilize such Fe(N x H y ) species by hydrogen bonding with pendant bases so far resulted in shutdown of catalysis. 10 But, in fact, such secondary interactions might also be relevant for Nishibayashi's catalyst as indicated by selectivities obtained with 2,6-lutidinium acids ([LutH] + [X] À ) as the proton source. These strongly depend on the X À counter anion: NH 3 /H 2 (X À ) ¼ 7.0 (Cl À ), 0.9 (OTf À ), and 0.14 (BAr 4 À ).…”

Rational design of metalloenzymes: From single to multiple active sites

“…These catalysts can be designed and synthesized to mimic the catalytic site of natural metalloenzymes [5][6][7]. Meanwhile, it is difficult to incorporate secondary coordination sphere interactions into the models, which has achieved progress recently, such as the use of intramolecular hydrogen bonds and other non-covalent interactions to regulate the function [8][9][10][11][12][13][14][15]. Moreover, chemically synthesized models are lack of long-range interactions that are also critical for natural metalloenzymes to achieve high reactivity and selectivity [16].…”