Structural studies on manganese(III) and manganese(IV) complexes of tetrachlorocatechol and the catalytic reduction of dioxygen to hydrogen peroxide
Structural studies on manganese(III) and manganese(IV) complexes of tetrachlorocatechol and the catalytic reduction of dioxygen to hydrogen peroxide
The mononuclear complexes (Bu4N)[Mn(Cl(4)Cat)(2)(H2O)(EtOH)] and (Bu4N)(2)[Mn(Cl(4)Cat)(3)] (H(2)Cat = 1,2-dihydroxybenzene) have been synthesised and characterised by X-ray diffraction. This work provides a direct, independent, synthesis of these complexes and an interesting example of how solvent effects can promote the formation of either a manganese(III) or manganese(IV) complex of the same ligand. The characterisation of (Bu4N)[Mn(Cl(4)Cat)(2)(H2O)(EtOH)] supports previous work that manganese(III) is extremely reluctant to form tris (catecholato) complexes due to the short 'bite distance' of catecholate oxygen atoms (2.79 Angstrom) which are unable to span the elongated coordination axes of the Jahn-Teller distorted Mn(III) ion and explains the 2:1 and 3:1 tetrachlorocatechol: manganese ratios in the Mn(III) and Mn(IV) complexes, respectively. Hydrogen peroxide production using dioxygen and hydroxylamine as substrates in acetonitrile/water mixtures, under ambient conditions, can be demonstrated with both complexes, suggesting that neither labile coordination sites nor the oxidation state of the manganese are important to the catalytic system. Turn over frequencies (TOF, moles of H2O2, per moles of manganese per hour) of similar to10000 h(-1) are obtained and this compares very favourably with the commercial production of hydrogen peroxide by the autoxidation of 2-ethylanthrahydroquinone (AO process).
manganese, tetrachlorocatechol, catecholate complexes, hydrogen
peroxide, hydroxylamine, dioxygen activation catalysttransition-metal complexes, single-molecule magnets, valencetautomerism, reversible binding, ribonucleotide reductase, semiquinoneligands, epr spectroscopy, globiformis cm-2, oxidation, catechol
2494-2502
Sheriff, Tippu S.
183de133-ff6b-4ac3-a9f0-938fdd2bf089
Carr, Pamela
d88129f9-0293-43e8-a146-539981f15582
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Hursthouse, Michael B.
57a2ddf9-b1b3-4f38-bfe9-ef2f526388da
Lesin, Jocelyne
5ef5bab7-9c43-49f0-83d6-cd1d350d591d
Light, Mark E.
cf57314e-6856-491b-a8d2-2dffc452e161
5 July 2004
Sheriff, Tippu S.
183de133-ff6b-4ac3-a9f0-938fdd2bf089
Carr, Pamela
d88129f9-0293-43e8-a146-539981f15582
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Hursthouse, Michael B.
57a2ddf9-b1b3-4f38-bfe9-ef2f526388da
Lesin, Jocelyne
5ef5bab7-9c43-49f0-83d6-cd1d350d591d
Light, Mark E.
cf57314e-6856-491b-a8d2-2dffc452e161
Sheriff, Tippu S., Carr, Pamela, Coles, Simon J., Hursthouse, Michael B., Lesin, Jocelyne and Light, Mark E.
(2004)
Structural studies on manganese(III) and manganese(IV) complexes of tetrachlorocatechol and the catalytic reduction of dioxygen to hydrogen peroxide.
Inorganica Chimica Acta, 357 (9), .
(doi:10.1016/j.ica.2003.09.032).
Abstract
The mononuclear complexes (Bu4N)[Mn(Cl(4)Cat)(2)(H2O)(EtOH)] and (Bu4N)(2)[Mn(Cl(4)Cat)(3)] (H(2)Cat = 1,2-dihydroxybenzene) have been synthesised and characterised by X-ray diffraction. This work provides a direct, independent, synthesis of these complexes and an interesting example of how solvent effects can promote the formation of either a manganese(III) or manganese(IV) complex of the same ligand. The characterisation of (Bu4N)[Mn(Cl(4)Cat)(2)(H2O)(EtOH)] supports previous work that manganese(III) is extremely reluctant to form tris (catecholato) complexes due to the short 'bite distance' of catecholate oxygen atoms (2.79 Angstrom) which are unable to span the elongated coordination axes of the Jahn-Teller distorted Mn(III) ion and explains the 2:1 and 3:1 tetrachlorocatechol: manganese ratios in the Mn(III) and Mn(IV) complexes, respectively. Hydrogen peroxide production using dioxygen and hydroxylamine as substrates in acetonitrile/water mixtures, under ambient conditions, can be demonstrated with both complexes, suggesting that neither labile coordination sites nor the oxidation state of the manganese are important to the catalytic system. Turn over frequencies (TOF, moles of H2O2, per moles of manganese per hour) of similar to10000 h(-1) are obtained and this compares very favourably with the commercial production of hydrogen peroxide by the autoxidation of 2-ethylanthrahydroquinone (AO process).
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More information
Published date: 5 July 2004
Keywords:
manganese, tetrachlorocatechol, catecholate complexes, hydrogen
peroxide, hydroxylamine, dioxygen activation catalysttransition-metal complexes, single-molecule magnets, valencetautomerism, reversible binding, ribonucleotide reductase, semiquinoneligands, epr spectroscopy, globiformis cm-2, oxidation, catechol
Identifiers
Local EPrints ID: 20319
URI: http://eprints.soton.ac.uk/id/eprint/20319
ISSN: 0020-1693
PURE UUID: 159b909d-6e46-490d-ab86-d70da02c8376
Catalogue record
Date deposited: 17 Feb 2006
Last modified: 16 Mar 2024 03:05
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Contributors
Author:
Tippu S. Sheriff
Author:
Pamela Carr
Author:
Jocelyne Lesin
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