The elusive abnormal CO<sub>2</sub> insertion enabled by metal-ligand cooperative photochemical selectivity inversion.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29563551.
- Also identified by DOI 10.1038/s41467-018-03239-3 and PMC identifier 5862843.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Direct hydrogenation of CO<sub>2</sub> to CO, the reverse water-gas shift reaction, is an attractive route to CO<sub>2</sub> utilization. However, the use of molecular catalysts is impeded by the general reactivity of metal hydrides with CO<sub>2</sub>. Insertion into M-H bonds results in formates (MO(O)CH), whereas the abnormal insertion to the hydroxycarbonyl isomer (MC(O)OH), which is the key intermediate for CO-selective catalysis, has never been directly observed. We here report that the selectivity of CO<sub>2</sub> insertion into a Ni-H bond can be inverted from normal to abnormal insertion upon switching from thermal to photochemical conditions. Mechanistic examination for abnormal insertion indicates photochemical N-H reductive elimination as the pivotal step that leads to an umpolung of the hydride ligand. This study conceptually introduces metal-ligand cooperation for selectivity control in photochemical transformations.