Abstract of the Research Program:

The research interests in DM group are rooted in synthetic inorganic and organometallic chemistry with special emphasis on the use of environmentally benign and atom-efficient catalysts, mostly comprising of the main group and the 1st-row transition metals, for small molecule activation and conversion of abundant raw materials into value-added chemicals. We are also interested in energy storage and on-demand energy production, biomass conversion, and materials synthesis. Students in this group get to learn the necessary skills for preparing organic, organometallic, and inorganic compounds, the state-of-the-art spectroscopic and analytical tools for characterization, and experience with kinetic techniques needed to identify viable reaction mechanisms.

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Research Program: The research program in our group is versatile and revolves around the broad theme of ‘synthetic organometallic chemistry for homogeneous catalysis’. The maximum effort at present goes to the synthesis, structure, reactivity, and catalytic applications of the earth-abundant and non-toxic main group and the first-row transition metal complexes. The target is to precisely control the reactivity using knowledge-based ligand- and complex design. The desired catalysts or pre-catalysts are subjected to activate relatively inert chemical bonds (e.g., C-H, N-H, Si-H, H-H) that are pertinent to a wide range of energy-related problems. We are also concerned with the interaction of these compounds with energy-related small molecules such as CO, CO2, and H2. A notable example could be the heavier alkaline earth metals such as calcium-mediated catalysis. Besides earth abundance, biocompatibility is another appealing feature of calcium. Once neglected for their salt-like behavior, organometallic chemistry of the heavier alkaline earths has come a long way since the introduction of sterically bulky and chelating ligands offering better control and understanding of the coordination environment. Well defined molecular calcium hydrides are of special interest lately due to their potential application in small molecule activation and homogeneous catalysis such olefin hydrogenation, which has been the forte of heavy and toxic late transition metals. However, the synthetic challenge lies in the detrimental Schlenk equilibrium and the high lattice energy of [CaH2]Ꚙ. We are actively in the search for stable and isolable molecular calcium hydrides or their immediate precursors to look out for their reactivity and catalytic application. Another interesting project we are involved in is the redox catalysis of bismuth. Despite being surrounded by some heavy, toxic, or radioactive elements, bismuth is surprisingly less-toxic and biocompatible. Another engaging feature of bismuth is its relatively easy redox switch between variable oxidation states (six distinct metal-centered oxidation states are theoretically accessible), a typical transition metal-like behavior. The Bi(III)/(V) couple in particular can be thought of orchestrating a catalytic cycle driven by steps like oxidative addition/reductive elimination. Choosing an appropriate ligand platform judiciously is as crucial as hitting the right metal system for successful catalysis. We take a classical approach by designing our case-specific own ligands keeping in mind the criteria like easy accessibility, tunability, and robustness. To name a few, we are at present nurturing with a set of hybrid ligands comprising of a monoanionic cyclopentadienyl/Indenyl/Fluorenyl ring with a tethered N-heterocyclic carbene moiety. We are also working towards developing a non-palindromic pincer-type monoanionic ligand framework with a flexible backbone that can bind both in a meridional (mer-) and facial (fac-) fashion depending on the metal type and the presence of other co-ligands. In many cases, the compounds of interest contain reactive or unstable components (e.g., radicals, hydrides, multiple bonds, etc.). Accordingly, we utilize various anaerobic synthetic protocols including Schlenk techniques and inert atmosphere gloveboxes and manipulate the reagents and solvents appropriately. We pay thorough attention and fully characterizing any newly synthesized compounds both in solution as well as in the solid-state. This includes analyses by NMR spectroscopy, FT-IR spectroscopy, EPR spectroscopy, mass spectrometry, cyclic voltammetry, single-crystal X-ray diffraction, and elemental analysis.