Dioxotungsten() complexes with isoniazid-related hydrazones as (pre)catalysts for olefin epoxidation: solvent and ligand substituent effects

• Published in: RSC advances 2016-01, Vol.6 (43), p.36384-36393
• Main Authors: Vrdoljak, Vinja, Pisk, Jana, Prugoveki, Biserka, Agustin, Dominique, Novak, Predrag, Matkovi-alogovi, Dubravka
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Coordination chemistry; Diffraction; Dimers; Epoxidation; Hydrazones; Molecular structure; Olefins; Thermogravimetric analysis; X-rays
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c6ra05067k

The mononuclear dioxotungsten( vi ) complexes [WO 2 (L 3OMe )(D)] ( 1a and 1b ), [WO 2 (L 4OMe )(D)] ( 2a and 2b ) and [WO 2 (L H )(D)] ( 3a and 3b ) (D = EtOH ( 1a3a ) or MeOH ( 1b3b ); L 3OMe = 3-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, L 4OMe = 4-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, L H = 2-oxybenzaldehyde isonicotinoyl hydrazonato) were synthesized by the reaction of [WO 2 (acac) 2 ]0.5C 6 H 5 Me with the respective isoniazid-related hydrazone. The compounds were characterized by microanalysis, FT-IR and NMR spectroscopy, thermogravimetric analysis, and powder X-ray diffraction method. The crystal and molecular structures of 1a , 1b , 3a and [WO 2 (acac) 2 ]0.5C 6 H 5 Me were determined by single crystal X-ray diffraction. The structures of 1a , 1b , 3a are mononuclear and form hydrogen bonded centrosymmetric dimers. In all three complexes, the dimers are also held together by interactions between aromatic rings. The catalytic performances (activity and selectivity) of 1a3a and 1b3b towards alkene epoxidation by tert -butyl hydroperoxide (TBHP) were investigated under different conditions. The catalytic performances (activity and selectivity) of the mononuclear dioxotungsten( vi ) complexes [WO 2 (L R )(D)] towards alkene epoxidation by tert -butyl hydroperoxide (TBHP) were investigated under different conditions.