The activation of carbon dioxide by metallylene [(dpp-bian)GaNa(DME)₂] (dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) under mild conditions is described. Furthermore, the reaction of the activation complex [(dpp-bian)Ga(CO₂)₂Ga(dpp-bian)][Na(DME)₂]₂(2) with diphenylketene, cyclohexyl isocyanate, and phenyl isocyanate leads to the elimination of carbon monoxide and the formation of derivatives of oxocarboxylic acid [(dpp-bian)GaOC(O)C(Ph)₂C(CPh₂)O][Na(DME)₂] (6) and carbamate derivatives [(dpp-bian)GaN(Cy)C(O)N(Cy)C(O)O]₂[Na(DME)₂]₂(7) and [(dpp-bian)GaN(Ph)C(O)O]₂[Na(DME)₂]₂(8), respectively. Complexes have been characterized by NMR, IR spectroscopy, elemental analysis, and X-ray diffraction analysis. Their electronic structures have been examined by DFT calculations. The possible mechanism of the modification reaction is proposed and supported by the investigation of¹³CO₂-enriched samples and DFT calculations.