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Open AccessArticle

Dioxygen Activation with Molybdenum Complexes Bearing Amide-Functionalized Iminophenolate Ligands

Institute of Chemistry, Inorganic Chemistry, University of Graz, Schubertstrasse 1, 8010 Graz, Austria
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Academic Editor: Antonella Dalla Cort
Molecules 2019, 24(9), 1814; https://doi.org/10.3390/molecules24091814
Received: 17 April 2019 / Revised: 7 May 2019 / Accepted: 9 May 2019 / Published: 10 May 2019
(This article belongs to the Special Issue Schiff Base and Its Metal Complexes)
Two novel iminophenolate ligands with amidopropyl side chains (HL2 and HL3) on the imine functionality have been synthesized in order to prepare dioxidomolybdenum(VI) complexes of the general structure [MoO2L2] featuring pendant internal hydrogen bond donors. For reasons of comparison, a previously published complex featuring n-butyl side chains (L1) was included in the investigation. Three complexes (13) obtained using these ligands (HL1HL3) were able to activate dioxygen in an in situ approach: The intermediate molybdenum(IV) species [MoO(PMe3)L2] is first generated by treatment with an excess of PMe3. Subsequent reaction with dioxygen leads to oxido peroxido complexes of the structure [MoO(O2)L2]. For the complex employing the ligand with the n-butyl side chain, the isolation of the oxidomolybdenum(IV) phosphino complex [MoO(PMe3)(L1)2] (4) was successful, whereas the respective Mo(IV) species employing the ligands with the amidopropyl side chains were found to be not stable enough to be isolated. The three oxido peroxido complexes of the structure [MoO(O2)L2] (911) were systematically compared to assess the influence of internal hydrogen bonds on the geometry as well as the catalytic activity in aerobic oxidation. All complexes were characterized by spectroscopic means. Furthermore, molecular structures were determined by single-crystal X-ray diffraction analyses of HL3, 13, 911 together with three polynuclear products {[MoO(L2)2]2(µ-O)} (7), {[MoO(L2)]4(µ-O)6} (8) and [C9H13N2O]4[Mo8O26]·6OPMe3 (12) which were obtained during the synthesis of reduced complexes of the type [MoO(PMe3)L2] (46). View Full-Text
Keywords: molybdenum; iminophenolate ligands; dioxygen activation; peroxido complexes molybdenum; iminophenolate ligands; dioxygen activation; peroxido complexes
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MDPI and ACS Style

Zwettler, N.; Ehweiner, M.A.; Schachner, J.A.; Dupé, A.; Belaj, F.; Mösch-Zanetti, N.C. Dioxygen Activation with Molybdenum Complexes Bearing Amide-Functionalized Iminophenolate Ligands. Molecules 2019, 24, 1814.

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