Peroxomolybdenum Complexes as Epoxidation Catalysts in Biphasic Hydrogen Peroxide Activation: Raman Spectroscopic Studies and Density Functional Calculations
✍ Scribed by Günter Wahl; Dirk Kleinhenz; Andrea Schorm; Jörg Sundermeyer; Ralf Stowasser; Christian Rummey; Gerhard Bringmann; Claudia Fickert; Wolfgang Kiefer
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 325 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Density functional calculations and Raman spectroscopic data were correlated with the unique catalytic epoxidation activity of peroxomolybdenum complexes [MoO(O 2 ) 2 (O-ER 3 )] (E N, P, As; R n-dodecyl) in a biphasic chloroform ± 1-octene/aqueous hydrogen peroxide system. Crystal structure determinations on [MoO(O 2 ) 2 (OPtBu 3 )(OCMe 2 )] and two complexes containing chelating hemilabile ether ± phosphane oxide and ether ± arsane oxide ligands [MoO(O 2 ) 2 -{iPr 2 E(O)CH 2 CH 2 OCH 3 }] (E P, As) are reported. A mechanistic study with these model complexes reveals the importance of free coordination sites for peroxide activation. Calculations and Raman spectroscopic data indicate the tendency of coordinatively unsaturated species [MoO(O 2 ) 2 (L)] to dimerize in noncoordinating solvents. The catalytic activity in the presence of water as competing ligand could be correlated with the calculated proton affinity of the ligands OER 3 (R N, P, As). Elucidation of the vibrational behavior of the structurally characterized peroxo complexes was supported by normal-coordinate analyses.