A simple coordination complex of uranium(III), a uranium tris(amide), can selectively couple gaseous CO to the linear ynediolate[OCCO]2− dianion, at room temperature and pressure, regardless of the reagent stoichiometry. This product exhibits further reactivity upon warming in the form of the addition of a C–H bond of a methyl group across the CC triple bond, this second carbon–carbon bond forming reaction generating a functionalised enediolate dianion.