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.
Diimido-, Imido(oxo)-, Dioxo-und Imido(alkyliden)-Halbsandwich-Verbindungen über selektive Hydrolyse und α؊H-Abstraktion an Organylkomplexen des sechswertigen Molybdäns und Wolframs
Bis(trimethylsily1) peroxide (BTSP) and tert-butyl hydroper-as oxygen source were achieved with the vanadates oxide (tBuOOH) were activated by various 0x0 and peroxo [VO(OR),] (R = fBu, iPr). Comparative selectivity and rate complexes of molybdenum, tungsten, and vanadium as cata-data for the stoichiometric and catalytic sulfoxidations of SSO lysts for the sulfoxidation of thianthrene 5-oxide (SSO). A mediated by the Mo0,L complex ( L = OPtBu:,, OPnOct3, screening of a number of phosphane oxide and amine oxide ONnBu,, ONnOct,) suggest that the bisperoxo metal comligands revealed that BTSP was most efficiently activated by plex is the active oxygen transfer species. the [MoO5(0PfBu3)] complex. The best results for tBuOOH Clrem.
Several new chiral triols 1a
−
c
with C
3 symmetry have been prepared in
enantiopure form
via a route involving the iterative catalytic asymmetric alkylation of
aldehydes by organozinc
reagents followed by diastereoselective hydroboration. Reactions
of these chiral triols with
titanates Ti(OR)4 and vanadates
V(O)(OR)3 are reported. The structure of the
binuclear
vanadium triolato(3−) complex
[V(O){(OCH-Et)3CH}]2
(12a) has been determined by X-ray
analysis. A series of model reactions was conducted to assess the
catalytic properties of the
chirally modified titanium and vanadium secondary alkoxides. The
reactions chosen were
the addition of diethylzinc and of trimethylsilyl cyanide to
benzaldehyde and the oxidation
of geraniol and of ethyl phenyl sulfide with tert-butyl
hydroperoxide. Only a moderate
asymmetric induction was found in some model reactions catalyzed by
titanium complexes
11a,b. On the other hand, a very efficient
chemoselective oxidation of sulfides to sulfoxides
with tert-butyl hydroperoxide was possible in the presence
of vanadium complex 12a.
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