Editing Group 7 element (section)

=== Rhenium ===

The catalytic activity of Re(bpy)(CO)<sub>3</sub>Cl for carbon dioxide reduction was first studied by Lehn et al.<ref>{{Cite journal|last=Hawecker|first=Jeannot|date=1984|title=Electrocatalytic Reduction of Carbon Dioxide Mediated by Re(bipy)(CO)3Cl (bipy = 2,2'-bipyridine)|journal=J. Chem. Soc., Chem. Commun.|pages=328–330|doi=10.1039/C39840000328 }}</ref> and Meyer et al.<ref>{{Cite journal|last=Sullivan|first=B. Patrick|date=1985|title=One- and Two-electron Pathways in the Electrocatalytic Reduction of CO2 by fac-Re(bpy)(CO)3Cl (bpy = 2,2'-bipyridine)|journal=J. Chem. Soc., Chem. Commun.|pages=1414–1416|doi=10.1039/C39850001414 }}</ref> in 1984 and 1985, respectively. Re(R-bpy)(CO)<sub>3</sub>X complexes exclusively produce CO from CO<sub>2</sub> reduction with [[Faraday efficiency|Faradaic efficiencies]] of close to 100% even in solutions with high concentrations of water or [[Brønsted–Lowry acid–base theory|Brønsted acids]].<ref name=":2">{{Cite journal|last=Grice|first=Kyle|date=2014|title=Recent Studies of Rhenium and Manganese Bipyridine Carbonyl Catalysts for the Electrochemical Reduction of CO2|journal=Advances in Inorganic Chemistry|volume=66|pages=163–188|doi=10.1016/B978-0-12-420221-4.00005-6 |isbn=9780124202214 }}</ref>

The catalytic mechanism of Re(R-bpy)(CO)<sub>3</sub>X involves reduction of the complex twice and loss of the X ligand to generate a five-coordinate active species which binds CO<sub>2</sub>. These complexes will reduce CO<sub>2</sub> both with and without an additional acid present; however, the presence of an acid increases catalytic activity.<ref name=":2" /> The high selectivity of these complexes to CO<sub>2</sub> reduction over the competing [[Water splitting|hydrogen evolution reaction]] has been shown by [[density functional theory]] studies to be related to the faster kinetics of CO<sub>2</sub> binding compared to H<sup>+</sup> binding.<ref name=":3">{{Cite journal|last=Francke|first=Robert|date=2018|title=Homogeneously Catalyzed Electroreduction of Carbon Dioxide -- Methods, Mechanisms, and Catalysts|journal=Chemical Reviews|volume=118|issue=9 |pages=4631–4701|doi=10.1021/acs.chemrev.7b00459 |pmid=29319300 }}</ref>