CO2 insertion into discrete (TptBu,Me)M(pzR,R) complexes of divalent magnesium, calcium and ytterbium.

Distinct oxophilicity does not impact the insertion of carbon dioxide into the metal pyrazolato bond of discrete complexes (TptBu,Me)M(pzR2) (M = Mg, Ca, Yb; R = Me, iPr, tBu). However, the calcium and ytterbium carbamates [(TptBu,Me)M(μ-CO2·pzR2)]x (R = Me, iPr, tBu; x = 1,2) are only stable under a CO2 atmosphere, while the monomeric magnesium complex (TptBu,Me)Mg(CO2·pzMe,Me) releases CO2 at temperatures higher than 100 °C.