Quintuple bonds, first reported in Science by Power and his team in 2005, were a major discovery at the time, as quadruple bonds were believed to be the highest bond order possible between two atoms, and these were still relatively uncommon. Following Power and then Kempe’s reports of such species, interest has shifted to the reactivity of these compounds, to see if interesting species may be accessible through these very low-coordinate intermediates.
Here, Kempe has shown that his highly reducing compound is able to activate both carbon and sulfur dioxides – which may prove useful for removing these gases from pollutants. The CO2 was converted into an oxidised Cr-Cr bond containing bridging carbonyl groups, releasing dioxygen in the process. This is intriguing and, if it could be made catalytic, could be a nice way of converting carbon dioxide to a more useful gas. Interestingly, the weaker S-O bond in SO2 bond could not be cleaved in such a way, with a novel bridging dithionite being formed instead. This is unprecedented, and further study could glean some interesting mechanistic information from this complex.
The synthesis of unusual and highly reactive low-coordinate compounds such as these is often to referred to as purely fundamental ‘blue sky’ research, but articles such as these indicate the potential future usefulness of such studies, both for potential applications of these species and the mechanistic insight they could offer us.