Carbon Dioxide Fixation and Utilization

Ph.DDOCTOR OF PHILOSOPH

Selective two-electron reduction of carbon monoxide mediated by molybdenum complexes supported on an asymmetric phenol phosphine ligand

Our group has recently reported a monometallic Molybdenum complex supported by a terphenyl diphosphine ligand capable of undergoing multielectron reductive processes. Various oxidn. states of the metal center are stabilized by the ability of the ligand to accommodate different binding modes. For example, the arene π-system displays η^2, η^4, η^6 binding while one of the phosphine arms reversibly dissocs. To further study the significance of the hemilability of the ligand donor arms, a monometallic Mo dicarbonyl complex supported by an asym. terphenyl phosphine- phenol ligand (POH) framework has been isolated. Deprotonation and treatment of the (PMo(CO)_2OH) complex with KC_8 or K(C_(10)H_8) yields a reduced Mo species. Subsequent treatment of the reduced species with a silyl electrophile effected a two-electron reductive C-C coupling of the carbonyl moieties. Mechanism of the reaction and ligand effects will be discussed. This work could provide insights for the conversion of C1 feedstock to value- added products

Carbon Dioxide Mediated Stereoselective Copper-Catalyzed Reductive Coupling of Alkynes and Thiols

A simple protocol for the stereoselective copper-catalyzed hydrothiolation of alkynes under a CO₂ atmosphere has been developed. The stereoselectivity is determined by the presence/absence of a CO₂ atmosphere. The reaction system is robust and utilizes inexpensive, readily available substrates. A cyclic alkene/carboxylate copper complex intermediate is proposed as the key step in determining the stereoselectivity, and an equivalent amount of water is found to play an active role as a proton donor