|
Area of Research: Organometallics and Sustainable Catalysis
Catalyst (Homogeneous & Heterogeneous) development for… Ø (De)hydrogenation reactions Ø Hydrogen atuto-transfer reactions Ø C1-Chemistry (CO2 to value-added chemicals)
(De)hydrogenation and related reactions:
1. Homogeneous Catalysis: Rapid depletion of limited fossil fuels has directed a significant amount of human efforts to identify alternative renewable, green energy resources. It has been widely accepted that hydrogen as a fuel can be effective to curtail the energy crisis if produced at the proximity of usage without involving long-distance transportation. Thus, the most attractive and efficient hydrogen storage/release media are liquid organic hydrogen carriers (LOHCs), because they have relatively high hydrogen content and can easily be transported. In this context, extraction of H from abundant, renewable feedstocks via acceptorless dehydrogenation strategy (AD) is extremely important, but a thermodynamically uphill process. Traditionally, extraction of hydrogen atoms in adjacent positions in an organic molecule can be achieved either by the use of a stoichiometric amount of strong oxidants or a sacrificial hydrogen acceptors, which often produce copious waste. On the other hand, catalytic dehydrogenation with concomitant removal of dihydrogen is a superior strategy and has enabled the direct access to valuable intermediates. In this regard, design and development of new catalytic systems for fundamentally important synthetic transformations and energy storage applications is an intellectually stimulating challenge. PI had significantly contributed to catalyst design for various important reactions for both fundamental research and industrial application. Key Publications: 1. Cobalt-catalyzed acceptorless dehydrogenative coupling of aminoalcohols with alcohols: Direct access to pyrrole, pyridine and pyrazine derivatives. S. P. Midya, V. G. Landge, M. K. Sahoo, J. Rana and E. Balaraman*. Chem. Commun. 2018, 54, 90-93. 2. Reversed reactivity of anilines with alkynes in the rhodium-catalysed C–H activation/carbonylation tandem. S. P. Midya, M. K. Sahoo, V. G. Landge, P. R. Rajamohanan and E. Balaraman*. Nature Commun. 2015, 6, 8591-8601. 3. Catalytic transformation of alcohols to carboxylic acid salts and H2 using water as the oxygen atom source. E. Balaraman, E. Khaskin, G. Leitus and D. Milstein*. Nature. Chem. 2013, 5, 122-125. 4. Efficient hydrogenation of organic carbonates, carbamates, and formates indicates alternative routes to methanol based on CO2 and CO. E. Balaraman, C. Gunanathan, J. Zhang, L. J. W. Shimon and D. Milstein*. Nature. Chem. 2011, 3, 609-614. 5. Unprecedented catalytic hydrogenation of urea derivatives to amines and methanol. E. Balaraman, Y. Ben-David and D. Milstein*. Angew. Chem. Intl. Ed. 2011, 50, 11702-11705. 6. Synthesis of peptides and pyrazines from β-aminoalcohols via extrusion of H2 catalyzed by ruthenium pincer complexes. Ligand controlled selectivity. B. Gnanaprakasam, E. Balaraman, Y. Ben-David and D. Milstein*. Angew. Chem. Intl. Ed. 2011, 50, 12240-12244. 7. Direct hydrogenation of amides to alcohols and amines under mild conditions. E. Balaraman, B. Gnanaprakasam, L. J. W. Shimon and D. Milstein*. J. Am. Chem. Soc. 2010, 132, 16756-16758.
1. Transition-metal catalysed hydrogen transfer annulation strategy to heterocyclic scaffolds. A. Nandakumar*, S. P. Midya, V. G. Landge, E. Balaraman* Angew. Chem. Intl. Ed. 2015, 54, 11022-11034. 2. Iron-catalyzed dehydrogenation reactions and its applications in sustainable energy and catalysis. E. Balaraman,* A. Nandakumar, G. Jaiswal, M. K. Sahoo Catal. Sci. Technol. 2017, 7, 3177-3175. (Selected as ‘HOT’ article 2017, Cover picture article).
2. Heterogeneous Catalysis: Alternative ‘green’ approaches to traditionally employing stoichiometric reagents in industrially important reactions are extremely essential. In this direction, the key research objective of the chemical and pharmaceutical industries is to convert homogeneous catalytic reactions into heterogeneous versions through the attachment of catalytic sites on stable supports. Heterogeneous catalysts offer many advantages, over the homogeneous ones which include high recyclability, easy recovery from the reaction mixture and their use in continuous flow processes. Our approach involves a thermal decomposition of a molecular complex of a metal (abundant, economical 3d transition metals) on a carbon support to obtain supported robust nanocatalyst and have designed several environmentally benign catalytic reactions; in particular, acceptorless dehydrogenation and related reactions based on developed nanocatalysts. We have developed unprecedented unique core–shell architecture of iron nanocatalyst with a shell comprising of oxide and a core mainly of carbide synthesized by thermally pyrolyzing Fe:N-rich ligand on a graphitic oxide support. Interestingly, the microstructure of the final catalyst showed a surface lacking the encapsulating sheath of carbon commonly observed in earlier works. The unique microstructure also resulted in an exceptional catalytic property in oxidant-free and acceptorless dehydrogenation of N-heterocycles, relatively abundant alcohols, and amines with the concomitant generation of hydrogen gas (Fig 1). Similarly, manganese and cobalt-based nanocatalysts were prepared and used for sustainable catalysis. Key Publications: 1. Iron-based nanocatalyst for the acceptorless dehydrogenation reactions. G. Jaiswal, V. G. Landge, D. Jegadeesan* and E. Balaraman* Nature Commun. 2017, 8, 2147-2160. 2. Sustainable iron-catalyzed direct imine formation by acceptorless dehydrogenative coupling of alcohols with amines. G. Jaiswal, V. G. Landge, D. Jagadeesan* and E. Balaraman*. Green Chem. 2016, 18, 3232-3238.
C-1 Chemistry: 1. CO2 to Polymer The utilization of carbon dioxide (CO2) is an abundant, non-flammable, economical, and renewable C1 feedstock is of strategic importance for our dependence on depleting non-renewable fossil derivatives. One of the most attractive areas of CO2 utilization is its direct application as a renewable raw material for polymer synthesis, as large amounts of CO2 can be utilized to make value-added polymeric products. Depending on the reactivity and selectivity of the catalyst, up to 43 wt % (polypropylene carbonate) of the polymer mass derives from CO2 via copolymerization with propylene oxide (PO). Polycarbonate having a terminal hydroxyl group plays a role in their excellent adhesive properties and widely used as intermediates in the production of polyurethane. We are working on the development of novel catalysts and the optimization of reaction parameter (pressure, temperature, and time) for this transformation. Commercial process: Novomer and Covestro (DMC or bimetallic catalysts, higher pressure of CO2 and temperature (< 100 oC), and the complete details are not available. Gap analysis: The catalysts that operate at ambient temperature and low pressure of CO2 with good polymer selectivity are the main concern. Novelty: Our strategy allows these polymerizations to proceed with minimal additional energy input and greater control.
2. Catalytic conversion CO2 to methanol Meeting the growing energy demand and environmental issue of the current society, while avoiding resource depletion and CO2 emission, requires the development of a catalytic system for effective conversion of CO2 to methanol, as it can serve as an energy carrier as well as a versatile basic chemical. Owing to the rational tuning of reactivity and selectivity of homogeneous catalysts much attention has been paid to their utility in the selective hydrogenation of CO2. At present, we are working on hydrogenation of CO2 to methanol under mild reaction conditions using well-defined metal complexes. Key publications (Patent applications): 1. Phenanthroline based pincer complexes useful as catalysts for the preparation of methanol from carbon dioxide. E. Balaraman*, V. G. Landge, S. P. Midya, M. K. Sahoo and G. Jaiswal. |
|