Catalysts for selective aerobic oxidation under ambient conditions - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 229

ensemble of freely diffusing time-dependent and concentration-dependent
reactive intermediates, makes these oxidations difficult to control. 9
Many of these limitations are avoided if a reducing agent is used.
Indeed, a multitude of biological and abiological/industrial
oxidation processes use a reductant because the resulting peroxo and other
intermediate-redox-state forms of oxygen generally exhibit greater
reactivity. More significantly however, these reactive oxygen species are
frequently more selective and their chemistry more controllable, with or
without the involvement of metal centers, than the chemistry of the active
oxygen and oxygenated intermediate species operable during reductant-free
oxidations. However, if a reducing agent is required, its cost must be
factored into the overall economics, and this renders many an otherwise
potentially attractive process unworkable practically.
Given these points, it is no wonder that there has been and is now
considerable interest in developing molecules and materials that catalyze the
selective (non-radical chain) reductant-free oxidation of many classes of
organic substrates using only There are just a handful of
homogeneous catalysts for such processes, and despite the fact all of these
have one or more significant (rate, selectivity and/or stability) limitations,
each of these studies has garnered much attention. 1-7 Furthermore, none of
these systems functions effectively under ambient conditions (1 atm of air
o
and ~22 C). This is unfortunate because a major intellectual impetus as well
as programmatic or developmental driver of such catalytic chemistry is the
realization of materials (coatings, fabrics, cosmetics, others) that catalyze the
degradation of the ubiquitous toxic agents in our environment without
chemical or physical assistance (without the requirement for heat, light,
water, solvents, activators, etc.). 11-13 Such materials could economically
function in a host of locations (the home, the workplace, the car, etc.) for a
host of applications and thus benefit mankind. The toxic agents of relevance
include sulfur compounds (thioethers, thiols and with mustard
(formula: being one deleterious thioether of much
current national and international concern because it is a widely prevalent
chemical warfare agent. 14-20 Several nitrogen compounds, including
pyridine, nicotine, trimethyl amine, aldehydes, halogenated compounds and
other volatile organic compounds (VOCs) also constitute everyday threats to
human health. 11-13,21
This chapter summarizes quite recent research on a new type of system
based on the coinage metals that does in fact catalyze selective reducing-
agent-free oxidation of an important target substrate, 2-chloroethyl ethyl
sulfide (henceforth CEES for convenience), a very effective simulant for
mustard. 22,23 The review addresses the genesis of this new type of system
and its systematic experimental elaboration including a quite thorough
analysis of mechanism. In this context, the selectivity (virtually quantitative