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New Directions in Sustainable Catalysis by Metal Complexes

Periodic Reporting for period 3 - SUSCAT (New Directions in Sustainable Catalysis by Metal Complexes)

Reporting period: 2019-07-01 to 2020-12-31

Currently, many of the processes employed by the chemical, pharmaceutical and agrochemicals industries produce large amounts of waste; for example, the production of one kg of a pharmaceutical active ingredient generates on average 500 kg of waste. This waste has to be treated in order not to harm the environment, posing a substantial economic burden and depletion of our resources. Moreover, most processes are based on non-sustainable chemicals, such as fossil-derived compounds.

In another relevant direction, although hydrogen has long been regarded as an ideal alternative to overcome the drawbacks of fossil technology, its direct utilization is challenging, due to low volumetric energy density of hydrogen gas and potential safety issues.

In view of these issues there is an urgent need for the discovery of new, sustainable and green catalytic reactions, which do not generate waste, use sustainable starting materials, proceed under mild conditions, consume little energy, and do not harm the environment, aiming at replacing harmful waste-generating processes. Moreover, replacing the direct use of hydrogen gas by organic liquids capable of generation of hydrogen when needed, and being safely regenerated using hydrogen, is highly desirable.

Our objectives are (a) to design and develop new catalysts that enable novel sustainable and green reactions (b) Design and develop hydrogen carrier systems, based on readily available , inexpensive and renewable organic liquids, using the new catalysts that we develop.
We have invented a new approach to the activation of chemical bonds by metal complexes, based on special, “pincer” type ligands capable of cooperation with the metal center in making and breaking bonds of various substrates, and in that way transform them to valuable products. With this approach, we have already developed novel, environmentally friendly reactions useful for organic synthesis using sustainable starting compounds, such as alcohols. The reactions proceed under mild conditions, produce no waste, consume little energy and simplify significantly synthetic processes. Several of these novel reactions produce or consume hydrogen gas, valuable by itself, forming the the basis for new hydrogen carrier systems, one of which has already been pioneered.

We have designed and developed several green reactions useful for organic synthesis, with the aim to replace currently practiced polluting processes. Of particular interest is the development of reactions catalyzed by complexes of earth-abundant metals, which are readily available, inexpensive and generally less toxic that complexes of noble metals. We have made several breakthroughs in that direction, using pincer-type complexes of earth abundant manganese, iron, and cobalt. Our group has pioneered such reactions.

We are empasizing in our research the development of catalysts which are based on complexes of earth-abundant metals, which are radily available, inexpensive and generally less toxic than noble metals. We have made breakthroughs in that direction, using pincer-type complexes of earth abundant manganese, iron, and cobalt, leading to new green synthetic reactions catalyzed by these complexes.

We have already reported on several advances, including:

(a) New bond activation processes
(b) Several new reactions for green organic synthesis catalyzed by earth-abundant metal complexes
(c) Catalytic reactions of the potent green house gases carbon dioxide and nitrous oxide
(d) A novel Liquid organic hydrogen carrier system
"All of the accomplishments listed above are beyond the state of the art.

Results expected until the end of the project include:

(a) development of novel, efficient hydrogen storage systems based on a new liquid organic hydrogen carriers

(b) new catalytic ""dehydrogenative coupling"" reactions based on ammonia, for the synthesis of heterocyclic compounds

(c) new reactions based on carbon dioxide for organic synthesis

(d) the development of harmless organic surrogates of harmful widely used reactants.

(e) development of catalytic hydrogenation methodology for conversion of waste plastics,to useful chemicals
"