Solvent‐Free Epoxidation of Olefins Catalyzed by "[MoO2(SAP)]": A New Mode of tert‐Butylhydroperoxide Activation. Issue 2 (13th May 2012)

• Record Type: Journal Article
• Authors: Morlot, Julien; Uyttebroeck, Nicolas; Agustin, Dominique; Poli, Rinaldo
• Is Part Of: ChemCatChem. Volume 5:Issue 2(2013:Feb.)
• Page Start: 601
• Page End: 611
• Publication Date: 2012-05-13
• Subjects: Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201200068
• Languages: English
• ISSNs: 1867-3880

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The mononuclear molybdenum complexes [MoO₂(acac)₂] (<bold>1</bold>, acac=acetylacetonate), [MoO₂(SAP)(MeOH)] (<bold>2</bold>), and dinuclear oxomolybdic complexes [MoO₂L]₂ [L=salicylideneaminophenolato (SAP, <bold>5</bold>), salicylideneaminoethanolato (SAE, <bold>6</bold>), salicylideneaminomethylpropanolato (SAMP, <bold>7</bold>)] have been investigated as (pre)catalysts for the epoxidation of olefins under solvent‐free conditions, using <italic>tert</italic>‐butylhydroperoxide (TBHP, 70 % in water) as an oxidant. Complexes <bold>6</bold> and <bold>7</bold>, although active, are limited by ligand hydrolysis during the catalytic process, whereas complexes <bold>2</bold> and <bold>5</bold> are not altered under catalytic conditions and yield essentially the same selectivity and activity, which is not suppressed by excess MeOH. Although these catalysts are less active than <bold>1</bold>, their selectivity is higher (97–98 %). DFT calculations are consistent with the active form of the catalyst being the 5‐coordinate "[MoO₂(SAP)]". The oxidant is activated by forming a weak adduct stabilized by a very loose Mo⋅⋅⋅O interaction and a hydrogen bond, predisposing it to the oxygen transfer to external olefin by a mechanism closely related to Bartlett's epoxidation with peroxyacids.</p> </abstract>