Carbon dioxide exchange reactions involving early transition-metal NN-dimethylcarbamato compounds: reversible insertion of carbon dioxide into transition-metal–nitrogen σ-bonds

Transition-metal NN-dimethylcarbamato compounds ML*n, (where M = Ti, Zr and n= 4; M = Nb, Ta and n= 5), W2L*6 and W(NMe2)3L*3, (L*= O213CNMe2), react with 12CO2 to give MLn, W2L6 and W(NMe2)3L3, where (L = O212CNMe2), with an energy of activation ranging from ca. 54 ± 8kJ mol–1 for ZrL4 to ca. 96kJ mol–1 for W(NMe2)3L3; mixtures of MLn and ML*n scramble CO2 in the absence of an applied CO2 atmosphere.