Catalysts for selective aerobic oxidation under ambient conditions - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 261

CEES oxidation in PFPE media. Using as the Au source,
as the source, and transition metal sulfates as the transition
metal source, reactivity towards CEES oxidation was assessed in two types
of PFPE media: Galden D-02 ® , a perfluorinated polyether oil, and Fomblin
MF-300 ® , a perfluourinated polyether surfactant. was
synthesized using a literature procedure. 36 TEA is an abbreviation for tetra-
n

-ethylammonium cation.
Effect of amino acids on the rate of CEES oxidation. Using the same
procedure as in the previous section, the inhibitory effect of various amino
acids were evaluated in Fomblin MF-300 ® , a PFPE surfactant.
Competitive oxidation between CEES and THT using
Using similar reaction conditions as above, two different thioethers, GEES
and THT, were added simultaneously in equimolar amounts and the
reactivity was compared to that of CEES alone.

20. CONCLUSIONS

Diversity-based methods combined with mechanistic information on
currently successful catalytic systems for oxidations have led to the
discovery of catalysts that addresses two of the holy grails in catalysis and
oxidation: complexes that catalyze selective (non-radical-chain) oxidation by
without the requirement of a sacrificial reductant, and complexes that
catalyze rapid reactions with the ambient environment (room temperature
and 1.0 atmosphere of air). The reaction studied here is thioether (organic
sulfide) sulfoxidation via the “dioxygenase stoichiometry”:
(sulfoxide), and the principal catalyst in homogeneous
acetonitrile is (1). The selective sulfoxidation of
thioethers is of interest in decontamination (mustard destruction) and organic
synthesis. Extensive kinetics, product, spectroscopic studies have
established all the elementary processes in the mechanism and the detailed
aspects of the rate-limiting step which involves reaction of 1 with a molecule
of the thioether substrate. The limitations exhibited by this initial system in
acetonitrile solution, namely the presence of a significant induction period
and inhibition by the sulfoxide product, are eliminated by the use of other
solvents or developmentally attractive and nontoxic perfluoropolyether
(PFPE) media. These aerobic selective catalytic sulfoxidation reactions are
also co-catalyzed by some d-block ions. All the mechanistic and energetic
information established in this initial research reviewed here augurs well for
further logical development of this new environmentally attractive (green)
catalytic chemistry.