Research Projects

Current science is focused on research that provides modern amenities but also does so in a sustainable fashion. A key goal in these efforts is the production of essential chemicals with almost zero waste from environmentally safe precursors. At the same time, protocols that can be implemented in ambient conditions are desirable to minimize the carbon footprint of such processes. The solution to these targets is the development of new “green” catalysts. Most homogenous or heterogenous catalysts currently in use are based on transition metals. However, many metals are scarce and expensive and are obtained via energy-intensive mining. This proposal targets the development of p-block element-based homogenous catalysts for industrially relevant reactions such as atom-economic amine production from ammonia and alkenes and room-temperature hydrogenation reactions. The p-block elements in a low oxidation state can activate small molecules by oxidative addition (OA). However, their further participation in catalysis is hindered due to the thermodynamic stability of the product after OA. One of the key solutions is to enhance the reactivity of p-block elements in the native oxidation state by using structurally constrained ligands. This proposal combines the structural constraints with the redox recycling ability of group 15 elements. By applying constrained ligands on P(III), the non-trigonal geometry could be stabilized as the ground state geometry. The structural distortion from classical C3v symmetric P(III) center to non-trigonal Cs symmetry significantly decreases the LUMO energy level, imparting amphiphilic character to such molecules. This proposal will use the di-anionic pyridine-diamide pincer ligands to access cationic non-trigonal phosphorus compounds. The proposed project will be guided by quantum chemical calculations performed by our own group. The preliminary calculation showed that the P(III) center has both HOMO and LUMO characters. More importantly, it also showed that the HOMO-LUMO gap can be easily finetuned by ligand modifications, for example, using -C=S instead of -C=O in the ligand backbone. The advantage of the proposed ligand system is the ease of making such modifications. The cationic non-trigonal P(III)-compounds will be used for small molecule activation of various polar and non-polar single and multiple bonds. The thermodynamic calculations showed the feasibility of several different bond activation reactions. Interestingly, several reactions by the proposed compounds showed reversibility if the kinetic barrier is accessible. This is promising for using proposed cationic non-trigonal P(III) compounds as catalysts. These compounds will be used as catalysts for reduction reactions, hydrogenations, hydroamination, and photo-redox cross-coupling reactions. Further, the cationic non-trigonal complexes of Sb(III) and Bi(III) will be synthesized, and the catalytic properties will be investigated.