1384245-84-4Relevant articles and documents
Dioxomolybdenum(VI) complexes with naphtholate-oxazoline ligands in catalytic epoxidation of olefins
Traar, Pedro,Schachner, J?rg A.,Stanje, Bernhard,Belaj, Ferdinand,M?sch-Zanetti, Nadia C.
, p. 54 - 60 (2014)
Synthesis, characterization and catalytic epoxidation experiments of two new dioxomolybdenum(VI) complexes [MoO2(L)2] (3a-b) equipped with O,N-bidentate naphtholate-oxazoline ligands L = 2a-b are described. Ligands 2a-b (2a = 2-(4,5-dihydrooxazol-2-yl)naphthalen-1-ol, 2b = 2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)naphthalen-1-ol) were obtained via a two-step synthesis starting from 1-hydroxy-naphthoic acid. Complexes 3a-b were synthesized starting from [MoO2(acac)2] and obtained in good yields as air and moisture stable solids. The molecular structure of both complexes 3a-b were determined by single crystal X-ray diffraction analysis, showing the expected octahedral coordination of the Mo center by two bidentate ligands of 2a or 2b and two terminal oxo ligands. Interestingly, for complex 3b two different coordination isomers with regards to the orientation of the bidentate ligands (N,N-trans 3b and N,N-cis 3b'), were obtained in the solid state. Both complexes 3a-b show high catalytic activities and selectivities in the epoxidation of various terminal and internal olefins at low catalyst loadings of 0.05 mol% with tert-butylhydroperoxide. With cyclooctene TON of 5000 could be reached, for styrene selectivities of >90% were achieved.
Dioxomolybdenum(VI) complexes with pyrazole based aryloxide ligands: Synthesis, characterization and application in epoxidation of olefins
Schachner, J?rg A.,Traar, Pedro,Sala, Chris,Melcher, Michaela,Harum, Bastian N.,Sax, Alexander F.,Volpe, Manuel,Belaj, Ferdinand,M?sch-Zanetti, Nadia C.
scheme or table, p. 7642 - 7649 (2012/09/05)
Synthesis, characterization, and epoxidation chemistry of four new dioxomolybdenum(VI) complexes [MoO2(L)2] (1-4) with aryloxide-pyrazole ligands L = L1-L4 is described. Catalysts 1-4 are air and moisture stable and easy to synthesize in only three steps in good yields. All four complexes are coordinated by the two bidentate ligands in an asymmetric fashion with one phenoxide and one pyrazole being trans to oxo atoms, respectively. This is in contrast to the structure found for the related aryloxide-oxazoline coordinated Mo(VI) dioxo complex 5. This was confirmed by the determination of the molecular structures of complexes 1-3 by X-ray diffraction analyses. Compounds 1-4 show high catalytic activities in the epoxidation of various olefins. Cyclooctene (S1) is converted to its epoxide with high activity, whereas the epoxidation of styrene (S2) is unselective. Internal olefins (S3 and S4) are also acceptable substrates, as well as the very challenging olefin 1-octene (S5). Catalyst loading can be reduced to 0.02 mol % and the catalyst can be recycled up to ten times without significant loss of activity. Supportive DFT calculations have been carried out in order to obtain deeper insights into the electronic situation around the Mo atom.
