Iron(III) and cobalt(III) complexes with both tautomeric (keto and enol) forms of aroylhydrazone ligands: catalysts for the microwave assisted oxidation of alcohols

Manas Sutradhar; Elisabete C. B. A. Alegria; Kamran T. Mahmudov; M. Fátima C. Guedes da Silva; Armando J. L. Pombeiro

doi:10.1039/C5RA25774C

Iron(iii) and cobalt(iii) complexes with both tautomeric (keto and enol) forms of aroylhydrazone ligands: catalysts for the microwave assisted oxidation of alcohols†

Manas Sutradhar,*^a Elisabete C. B. A. Alegria,

^ab Kamran T. Mahmudov,^a M. Fátima C. Guedes da Silva^a and Armando J. L. Pombeiro*^a

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* Corresponding authors

^a Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
E-mail: manaschem@yahoo.co.in, pombeiro@tecnico.ulisboa.pt

^b Chemical Engineering Departament, ISEL-Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, 1959-007 Lisboa, Portugal

Abstract

Two Schiff bases derived from the condensation of 2-hydroxybenzohydrazide with 3,5-di-tert-butyl-2-hydroxybenzaldehyde (H₂L¹) or with 2,3-dihydroxy benzaldehyde (H₂L²) were used to synthesize the Fe(III) and Co(III) complexes [Fe(L¹)(HL¹)] (1) and [Co(L²)(HL²)] (2), respectively. The compounds were characterized by elemental analysis, IR, ESI-MS and single crystal X-ray analysis. Structural studies indicated the presence of both keto and enol tautomeric forms of the ligand in 1 and 2. The complexes (mainly 1) act as catalysts in the microwave-assisted solvent-free peroxidative oxidation (by tert-butylhydroperoxide, TBHP) of primary and secondary alcohols. A facile, efficient and selective synthesis of ketones was achieved with a yield up to 96% and a TON up to 500, after 30 min under low power (15 W) microwave irradiation (complex 1 as catalyst). 2-Pyrazinecarboxylic acid (Hpca) shows a promoting effect.

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DOI: https://doi.org/10.1039/C5RA25774C
Article type: Paper
Submitted: 03 Dec 2015
Accepted: 07 Jan 2016
First published: 13 Jan 2016

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RSC Adv., 2016,6, 8079-8088

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Iron(III) and cobalt(III) complexes with both tautomeric (keto and enol) forms of aroylhydrazone ligands: catalysts for the microwave assisted oxidation of alcohols

M. Sutradhar, E. C. B. A. Alegria, K. T. Mahmudov, M. F. C. Guedes da Silva and A. J. L. Pombeiro, RSC Adv., 2016, 6, 8079 DOI: 10.1039/C5RA25774C

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Iron(iii) and cobalt(iii) complexes with both tautomeric (keto and enol) forms of aroylhydrazone ligands: catalysts for the microwave assisted oxidation of alcohols†

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Iron(III) and cobalt(III) complexes with both tautomeric (keto and enol) forms of aroylhydrazone ligands: catalysts for the microwave assisted oxidation of alcohols

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