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Catalysts 2018, 8(3), 114; https://doi.org/10.3390/catal8030114

Highly Active and Selective Supported Rhenium Catalysts for Aerobic Oxidation of n-Hexane and n-Heptane

1
Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
2
Materials Laboratory, Chemistry Centre, CQ-VR, University of Trás-os-Montes e Alto Douro (UTAD), 5001-801 Vila Real, Portugal
3
ADEQ, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, 1959-007 Lisboa, Portugal
*
Authors to whom correspondence should be addressed.
Received: 23 December 2017 / Revised: 13 March 2018 / Accepted: 13 March 2018 / Published: 15 March 2018
(This article belongs to the Special Issue New Trends in Scorpionate Catalysts)
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Abstract

A series of derivative C-scorpionate rhenium complexes, i.e., [ReCl2{NNC(O)C6H5}(Hpz)(PPh3)2] (A) (where Hpz is pyrazole), [ReCl2{NNC(O)C6H5}(Hpz)2(PPh3)] (B), [ReClF{NNC(O)C6H5}(Hpz)2(PPh3)] (C), and their precursor [ReOCl3(PPh3)2] (D), immobilized on 3-aminopropyl-functionalized silica have been prepared and used for neat O2 oxidation of n-hexane and n-heptane mainly to the corresponding alcohols and, in lower amounts, ketones. The supported catalyst C, with fluoro- and diazenido-ligands, exhibits the highest activity for both alkanes (overall turnover numbers (TONs) up to 3.8 × 103 and 2.5 × 103, for n-hexane and n-heptane, respectively) and can be reused in consecutive catalytic cycles. Improved conversion was observed after addition of hetero-carboxylate co-catalysts. A free-radical-based mechanism is proposed to explain the product formation. View Full-Text
Keywords: rhenium; scorpionate derivative; immobilization; supported catalysis; n-alkane; oxidation; molecular oxygen; product selectivity; radical mechanism rhenium; scorpionate derivative; immobilization; supported catalysis; n-alkane; oxidation; molecular oxygen; product selectivity; radical mechanism
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Mishra, G.S.; Alegria, E.C.B.A.; Pombeiro, A.J.L.; Martins, L.M.D.R.S. Highly Active and Selective Supported Rhenium Catalysts for Aerobic Oxidation of n-Hexane and n-Heptane. Catalysts 2018, 8, 114.

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