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Synthesis of Cyclic Carbonates Catalysed by Aluminium Heteroscorpionate Complexes |
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| Authors: | Javier Martínez Dr. José A. Castro‐Osma Amy Earlam Dr. Carlos Alonso‐Moreno Prof. Antonio Otero Dr. Agustín Lara‐Sánchez Prof. Michael North Dr. Antonio Rodríguez‐Diéguez |
| Affiliation: | 1. Green Chemistry Centre of Excellence, Department of Chemistry, The University of York, York, YO10 5DD (UK);2. Departamento de Química Inorgánica, Orgánica y Bioquímica, and Centro de Innovación en Química Avanzada (ORFEO‐CINQA), Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla‐La Mancha, Campus Universitario, 13071 Ciudad Real (Spain);3. Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada. Avda de Fuentenueva s/n, 18071 Granada (Spain) |
| Abstract: | New aluminium scorpionate based complexes have been prepared and used for the synthesis of cyclic carbonates from epoxides and carbon dioxide. Bimetallic aluminium(heteroscorpionate) complexes 9 – 14 were synthesised in very high yields. The single‐crystal X‐ray structures of 12 and 13 confirm an asymmetric κ2‐NO‐μ‐O arrangement in a dinuclear molecular disposition. These bimetallic aluminium complexes were investigated as catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide in the presence of ammonium salts. Under the optimal reaction conditions, complex 9 in combination with tetrabutylammonium bromide acts as a very efficient catalyst system for the conversion of both monosubstituted and internal epoxides into the corresponding cyclic carbonates showing broad substrate scope. Complex 9 and tetrabutylammonium bromide is the second most efficient aluminium‐based catalyst system for the reaction of internal epoxides with carbon dioxide. A kinetic study has been carried out and showed that the reactions were first order in complex 9 and tetrabutylammonium bromide concentrations. Based on the kinetic study, a catalytic cycle is proposed. |
| Keywords: | aluminium complexes carbon dioxide catalysis cyclic carbonates epoxides |