X‑ray Absorption Spectroscopy and Theoretical Investigation of the Reductive Protonation of Cyclopentadienyl Cobalt Compounds

Cobalt­(III) hydrides, formed via protonation of basic cobalt­(I) centers, have long been recognized as key intermediates in the electrocatalytic reduction of protons to hydrogen. An understanding of the structural and electronic factors that govern their formation is key to developing more efficien...

Full description

Saved in:
Bibliographic Details
Published in:Inorganic chemistry 2019-01, Vol.58 (2), p.1167-1176
Main Authors: McLoughlin, Elizabeth A, Giles, Logan J, Waymouth, Robert M, Sarangi, Ritimukta
Format: Article
Language:English
Subjects:
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
MATERIALS SCIENCE
Citations: Items that this one cites
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Cobalt­(III) hydrides, formed via protonation of basic cobalt­(I) centers, have long been recognized as key intermediates in the electrocatalytic reduction of protons to hydrogen. An understanding of the structural and electronic factors that govern their formation is key to developing more efficient and potent catalysts. A combination of Co K-edge X-ray absorption spectroscopy, extended X-ray absorption fine structure, density functional theory (DFT), and time-dependent DFT methods have been used to investigate several cyclopentadienyl (Cp) Co­(III)­L (L = ligand) species and their two-electron reduced Co­(I) analogues. The results reveal that when L is strongly π-accepting, the reduced species demonstrates strong backbonding between the electron-rich Co­(I) center and the ligand L, resulting in a weakly basic Co center that does not protonate to form a Co­(III)–H. In contrast, a weakly π-accepting or σ-donating ligand system results in an electron-rich Co­(I) center, which is readily protonated to form a Co­(III)–H. This study reveals the strength of a combined X-ray spectroscopy/theory method in understanding the role of ligands in tuning the electronic structure and subsequent reactivity of the metal center.
ISSN:0020-1669
1520-510X
DOI:10.1021/acs.inorgchem.8b02475