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Title: Epoxidation and catechol oxidation catalytic processes promoted by manganese(III) complexes of salen-type ligands
Authors: Guha, Averi
Zangrando, Ennio
Chandra, Arpita
Keywords: Mononuclear Manganese(III) complexes;Catecholase activity;Epoxidation catalyst
Issue Date: Feb-2021
Publisher: NISCAIR-CSIR, India
Abstract: Four new mononuclear manganese(III) complexes namely 1, 2, 3 and 4 of salen-type ligands H2L1-H2L4 (ligands were obtained in situ via Schiff-base condensation of 2-formyl-6-hydroxymethyl-4-methylphenol and amines cyclohexane-1,2-diamine, 2-methylpropane-1,2-diamine, propane-1,2-diamine and ethane-1,2-diamine, respectively) have been synthesised and characterised by routine physicochemical techniques. 1 is further characterised by X-ray single crystal structure analysis. Catalytic efficiencies of the complexes as epoxidation catalysts (substrates: styrene and (E)-stilbene; terminal oxidants: PhIO/NaOCl; solvent: MeCN /dicholorometane) and as catalysts for oxidation of catachol (substrates: 3,5-di-tert-butylcatechol (3,5-DTBC); solvent: methanol) have been evaluated. In both cases the catalytic efficiency increases on going from 4-1 although the actual mechanisms in those two catalytic reactions are completely different. However, the observations have been rationalized on the basis of steric and electronic factors exerted by the alkyl substituents present on the imine back-bone of the salen-type ligands. This study also verifies that there is at least another active epoxidizing species, [Cl–O–Mn(III)(salen)X] in addition to the discrete Mn(V)=O(salen) species in epoxidation of olefins depending upon the terminal oxidants employed.
Page(s): 169-176
ISSN: 0975-0975(Online); 0376-4710(Print)
Appears in Collections:IJC-A Vol.60A(02) [February 2021]

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