The Elusive Cyanoformate: An Unusual Cyanide Shuttle

摘要

CO2 makes up just 0.04 % of the earth's atmosphere and is essential for all life on earth. Nevertheless, it is the major anthropogenic greenhouse gas. Consequently, significant scientific effort has been devoted to establishing CO2 as a cheap and readily available carbon feedstock. The electro-philic nature of CO2 is exploited in its catalytic reduction to formates by either enzymes, well-defined metal complexes, or metal oxides. Nanoporous materials such as amine-grafted metal-organic frameworks (MOFs) can reversibly bind CO2 and thus allow regeneration of the sorbent. It comes as a surprise that CO2 complexes with small nucleo-philic anions, such as halides or pseudo-halides (e.g. OH , CN~-, OCN~-, SCN~-, and N3~-) have not been thoroughly studied to date. The only well-characterized halide/pseudo-halide CO2 species are hydrogen carbonate (old: bicarbonate) [HO-CO2]" and fmorocarbonate [FCO2]~-. In this context, a recent report by Clybourne, Tuononen and co-workers on the preparation of the elusive cyanoformate anion warrants particular attention (Scheme 1).