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The development of new catalytic systems that allow for rapid and selective transformations have a significant impact in the chemical industry, both in fine and bulk chemical production. In this context, organometallic compounds have become an established synthetic tool for the synthesis of useful molecules.
Our research interests focus on development of novel homogeneous catalytic systems that allow efficient and environmentally benign synthetic transformations of simple molecules into useful building blocks for materials and medicinal compounds. Our research program is dealing with the synthesis of novel N-heterocyclic carbene (NHC) ligands tethered with a cyclopentadienyl unit and their coordination to middle and late transition metals. NHCs have become a key class of ligands in organometallic chemistry due to the application of their metal-based compounds in a vast number of catalytic reactions. Their structural versatility and functionalization enables them to display an array of exploitable and tuneable properties. Recently, we discovered a straightforward route to unsubstituted and substituted-cyclopentadienyls functionalized N-heterocyclic carbenes (Cp-NHCs). The coordination of these novel ligands to transition metals such as iridium, ruthenium, rhodium and molybdenum shows the versatility of the new ligands. These novel metal complexes are effective catalysts in a wide set of reactions implying C-H activations. In particular, they have shown high catalytic activity toward transfer hydrogenation, -alkylation of secondary alcohols with primary alcohols, and amination of primary alcohols. The design of the asymmetric version of these reactions is one of the most attractive features that we are now being explored in our group.
The reduction of a variety of functional groups using hydrogen as a reducing agent and high-valent metal oxo species as catalysts is another important topic that we have been developing in our laboratory. We exploited catalysts normally used for oxidations, such as olefin epoxidation and olefin transfer. In 2005, we developed the reduction of carbonyl groups by using metal oxides as catalyst and silanes as reducing agents. Recently, we have extended the role of these catalysts to reductive processes using hydrogen, a cheaper and more convenient reducing agent than silane. The catalytic systems are capable of catalysing the selective hydrogenation of alkynes to alkanes-a challenging task in organic synthesis. Our last discovery deals with the selective reduction of nitroarenes by using a simple, inexpensive, clean and reusable catalytic system. This finding is remarkable since the selective reduction of a nitro group when other reducible functions are present is a difficult process, especially when hydrogen is used as reducing agent.
- Kandepi V. V. Krishna Mohan, Post-doc
- Patrícia M. Reis, Post-doc
- André P. da Costa, PhD student
- Jose A. Brito Castro, PhD student
- João Cardoso, BI
- João Mexia, BII
- Reis P. M. and Royo B (2009) “Chemoselective hydrogenation of nitroarenes and deoxygenation of pyridine N-oxides with H2 catalyzed by MoO2Cl2.” Tetrahedron Letters 50(8): 6960-6966.
- Costa A. P., Viciano M., Sanaú M., Merino S., Tejeda J., Peris E., Royo B. (2008) “First Cp*-functionallized N-heterocyclic carbene and its coordination to iridium. Study of the catalytic properties.” Organometallics 27(6):1305-1309.
- Kandepi V. V. K. M., Costa A. P., E. Peris, B. Royo (2009) “Molybdenum(II) complexes containing cyclopentadienyl-functionlaized N-heterocyclic carbenes: synthesis, structure and application in olefin epoxidation.” Organometallics 28(15): 4544-4549.
For further information please visit the laboratory's website
A Catálise Homogénea é uma ciência fundamental para o desenvolvimento da indústria de química fina. Os produtos de química fina empregam-se em indústrias tão variadas como as dos cosméticos, dos aditivos alimentares, das fragrâncias, da agroquímica e usam-se também na indústria farmacêutica. A complexidade estrutural dos produtos deste sector requer um número elevado de etapas sintéticas e provoca, em geral, a geração de uma grande quantidade de resíduos. A diminuição ou eliminação dos resíduos dos processos produtivos é o desafio mais importante da indústria química. Um processo sem resíduos, um processo verde, requer uma selectividade de 100%, isto é, processos sem reacções laterais e uma selectividade atómica de 100%. Os processos catalizados homogeneamente por complexos de metais de transição são os melhores candidatos para cumprir estas condições ideais.
A investigação realizada neste laboratório dirige-se ao desenho e modificação de catalisadores baseados em compostos organometálicos de metais de transição e a sua aplicação em diferentes processos catalíticos com o objectivo final de contribuir ao desenvolvimento de processos sustentáveis.