# Hydrogen Radical Chemistry at High-Symmetry {2Fe2S} Centers Probed Using a Muonium Surrogate

## TL;DR

This study uses muonium to probe hydrogen radical chemistry in high-symmetry iron-sulfur clusters, revealing how radicals form and behave in these systems.

## Contribution

The paper introduces a novel method using muonium to study hydrogen radical behavior in {2Fe2S} systems without requiring closed-shell precursors.

## Key findings

- High-symmetry {2Fe2S} systems form bridging radicals on the time scale of the muon experiment.
- The computational approach identifies all possible addition sites in solid-state samples.
- Muonium provides unique insights into hyperfine couplings and molecular structure.

## Abstract

Redox-active metal
hydrides are of central importance
in the development
of novel hydrogen generation catalysts. Direct insight into open-shell
hydrides is, however, difficult to obtain. One approach to gain this
information is to use muonium (Mu• = μ+ e–) as a surrogate for the hydrogen radical.
The chemistry of Mu• is analogous to H•; however, the species provides a highly sensitive probe through
detection of the positrons arising from the muon decay (with a lifetime
of ∼2.2 μs) and can therefore provide unique information
about hyperfine couplings and thus molecular structure. Using this
approach, we demonstrate here that the high-symmetry {2Fe2S} systems
Fe2(edt)(CO)4L2 (edt = ethane-1,2-dithiolato;
L = CO, PMe3, CN–) form bridging radicals
directly on the time scale of the muon experiment. We also extend
our computational approach to detail all of the possible addition
sites in solid state samples.

Muonium (Mu• = μ+ e−) can be
used as a surrogate for the hydrogen radical,
with decay of the muon allowing probing of sites of hydride formation
without needing access to closed-shell precursors. Here, we use this
approach to examine high-symmetry {2Fe2S} systems which form bridging
radicals directly on the time scale of the muon experiment. By extending
our modeling approach, we can scale this analysis to a wide range
of significant organometallic systems.