Dinitrogen Cleavage and Functionalization with Carbon Dioxide in a Dititanium Dihydride Framework.

The activation and functionalization of dinitrogen (N) with carbon dioxide (CO) are of great interest and importance but highly challenging. We report here for the first time the reaction of N with CO in a dititanium dihydride framework, which leads to N-C bond formation and N-N and C-O bond cleavage. Exposure of a dinitrogen dititanium hydride complex {[(PNP)Ti](-:-N)(-H)} () (PNP = 4,5-bis(diisopropylphosphino)-2,7,9,9-tetramethyl-9H-acridin-10-ide) to a CO atmosphere at room temperature rapidly yielded a nitrido/,-dicarboxylamido complex {[(PNP)Ti](-N)[-N(CO)]} (, 28%) and a diisocyanato/dioxo complex {[(PNP)Ti](NCO)(-O)} (, 52%) with release of H. When the reaction of with CO (1 atm) was carried out at -50 °C, complex was selectively formed in 82% yield within 5 min. Heating at 80 °C under 1 atm CO for 30 min afforded in 67% yield. When was allowed to react with 1.5 equiv of CO at room temperature, an isocyanato/nitrido/oxo complex {[(PNP)Ti](NCO)(-N)(-O)} () was exclusively formed in 89% yield within 5 min. The reaction of with CO at room temperature almost quantitatively yielded the dioxo/diisocyanato complex within 5 min. The mechanistic details were clarified by the N- and C-labeled experiments and density functional theory (DFT) calculations, providing unprecedented insights into the reaction of N with CO. A titanium-mediated cycle for the synthesis of trimethylsilyl isocyanate MeSiNCO from N, CO, and MeSiCl using H as a reducing agent was also established.