A sulfonated Schiff base dimethyltin(iv) coordination polymer: synthesis, characterization and application as a catalyst for ultrasound- or microwave-assisted Baeyer–Villiger oxidation under solvent-free conditions. Issue 81 (17th August 2016)

• Record Type: Journal Article
• Authors: Martins, Luísa M. D. R. S.; Hazra, Susanta; Guedes da Silva, M. Fátima C.; Pombeiro, Armando J. L.
• Is Part Of: RSC advances. Volume 6:Issue 81(2016)
• Page Start: 78225
• Page End: 78233
• Publication Date: 2016-08-17
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c6ra14689a
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : The sulfonated Schiff base dimethyltin(iv ) coordination polymer is an efficient heterogeneous catalyst for the peroxidative Baeyer–Villiger oxidation of ketones, under ultrasound or microwave irradiation and solvent- and additive-free conditions. Abstract : The synthesis and crystal structure of the new dimethyltin(iv ) compound [SnMe2 (HL)(CH3 OH)] n ·(0.5 n CH3 OH) (1 ) derived from the Schiff base 2-[(2, 3-dihydroxyphenyl)methylideneamino]benzenesulfonic acid (H3 L) are described. Despite having six potentially donating centres (one imine nitrogen, two phenoxo and three sulfonate oxygen atoms), the monoprotonated dianionic ligand (HL 2− ) behaves as an O, O, O-tridentate chelator. Single crystal X-ray diffraction revealed that1 is a 1D coordination polymer with every tin(iv ) ion bound to two methyl groups, a methanol molecule, two Ophenoxo and one μ-Osulfonate atom from HL 2− . The coordination polymer1 was applied as a heterogeneous catalyst for the Baeyer–Villiger oxidation of ketones to esters or lactones, using aqueous hydrogen peroxide as oxidant, under ultrasound (US) or microwave (MW) irradiation and solvent- and additive-free conditions. Overall conversions up to 76/82, 98/93, 93/89, 91/94, 83/90, 68/62 and 81/87% under US/MW irradiations were obtained with 3, 3-dimethyl-2-butanone, cyclopentanone, 2-methylcyclopentanone, cyclohexanone, 3-methylcyclohexanone, benzophenone and acetophenone, respectively. The catalyst can be recycled up to five cycles without losing appreciable activity.