Hydrosilylation of terminal alkynes by water soluble Rh(III) catalysts based on carboxylate-functionalized polydentate N-heterocyclic carbene ligands

Abstract

Resumen del póster presentado al Organometallic Chemistry Directed Towards Organic Synthesis (OMCOS) IUPAC International Symposium, celebrado en Sitges-Barcelona (España) del 28 de junio al 2 de julio de 2015.The optimization of a catalytic process has a relevant role in sustainable chemistry. In that sense, the use N-Heterocyclic (NHCs) carbene ligands has allowed the development of new catalysts with tunnable steric and electronic features leading in many cases to a substantial increase of the activity and selectivity of the processes. In general, polydentate functionalized NHC carbene ligands have been less studied than the mono- and bidentate NHCs, but its potential in catalysis is notorious. Our interest focuses on the synthesis of suitable precursors for polydentate NHCs ligands for the preparation of water-soluble catalysts, a much more sustainable reaction medium for catalytic processes of industrial interest. The hydrosilylation of C-C triple bonds is the most straightforward method for the preparation of vinylsilanes which are valuable building-blocks with important applications in organic synthesis. Metalcatalyzed hydrosilylation of terminal alkynes is an efficient and atom economical route to vinylsilanes. However, the control of the regio- and stereoselectivity of the reaction still remains an important challenge. Of the three possible isomers, the anti-Markovnikov anti-addition gives the least thermodynamically stable β-(Z)-vinylsilane isomer that have aroused great interest as an intermediate in organic synthesis. Thus, catalyst design is pivotal in order to overcome the stability of the β-(E) and α-vinylsilane isomers in favor of the less stable β-(Z). In this work, we have synthesized rhodium(III) and iridium(III) complexes containing the functionalized NHC-based ligand 2,2-bis(3-methyl-imidazol-1-il-2-ylidene)acetate, which are efficient catalysts precursor for the hydrosilylation of terminal alkynes to β-(Z)-vinylsilane derivatives with excellent yields and selectivities.Peer Reviewe