A bis-Pyrazolate Pincer on Reduced Cr Deoxygenates CO : Selective Capture of the Derived Oxide by Cr.

Reduction of the bis-(pyrazolyl)pyridine complex [LCr] with stoichiometric KC in THF produces a species that is reactive with CO to produce an aggregate composed of paramagnetic K L Cr (CO ) linked by KCl into a product of formula [K L Cr (CO )] ⋅2KCl. X-ray diffraction reveals a pincer hydrocarbon exterior and an inorganic interior composed of K , Cl and carbonate oxygens. Every Cr is five coordinate and square pyramidal, with the axial N donor weakly bonded to Cr due to the Jahn-Teller effect of a high spin d configuration. Reaction with CO confirms that carbonate here is derived from CO , that oxide is derived from CO , and that CO is indeed released, since it is not a competent ligand to Cr . Guiding principles for selectivity in CO reduction are deduced from the diverse successful molecular constructs to date.