The Synthesis And Properties Of VB Metal N-heterocyclic Carbene Complexes

In recent years, N-heterocyclic carbenes(NHC) as strong σ electron-donating ligands have attracted intense interesting because of their unique structure and chemical catalytical properties. N-heterocyclic carbenes present good properties such as structural diversification, electronic effects and steric effects are easy to control, etc. Therefore, NHC are widely used in organic synthesis, organometallic chemistry, coordination chemistry and other research fields.In this thesis we introduced the synthesis methods of imidazole salts and NHCs, and successfully isolated two free NHCs: 1,3- bis(2,6-diisopropylphenyl) imidazol-2-ylidend(IPr) and 1,3- bis(2,4,6-trimethylphenyl) imidazole-2- ylidend(IMes). Two novel NHC metal complexes [(IMes)2TaCl4][TaCl6] and [(IMes)2NbCl4][NbCl6] were prepared through the reactions of NHCs coordinated with TaCl5 and NbCl5. In addition, we synthesized IMesCO2 through activation of CO2 by IMes. This compound can react with TaCl5 to afford a new NHC metal complexe: IMesCO2TaCl5. These new complexes were characterized by Nuclear magnetic resonance spectrum, single crystal X-ray diffraction and elemental analysis.In the meantime, we studied the catalytic properties of these NHC metal complexes and found that they all can catalyze the reaction of propylene oxide and CO2. Especially, complex [(IMes)2NbCl4][NbCl6] can efficiently catalyze the polymerization of propylene oxide and CO2.