In a related case, CpMo(CO)3Me and tBuOOH first give the dioxo
complex, CpMo(O)2Me, then the isolable peroxide, CpMoO(h2-O2)
Me, both inactive for stoichiometric epoxidation (Scheme 3). The
latter is converted by tBuOOH to a reactive species, probably
CpMo(OH)(OOtBu)(h2-O2)Me, that transfers an O atom to the
alkene [15]. Both the methyl group and the Cp survive the oxidative
loss of the carbonyls as well as numerous catalytic cycles of
epoxidation.
These examples are sufficient to show that CO is one of the
easiest organometallic ligands to remove via oxidation. CO ligands
require back bonding for stable binding to a metal, but oxidation of
the metal greatly reduces the degree of back donation possible. This
effect also enhances the partial positive charge on the CO carbon
and so increases the tendency for nucleophilic attack at that carbon,
either by the solvent or the oxidant.
In a related case, CpMo(CO)3Me and tBuOOH first give the dioxo
complex, CpMo(O)2Me, then the isolable peroxide, CpMoO(h2-O2)
Me, both inactive for stoichiometric epoxidation (Scheme 3). The
latter is converted by tBuOOH to a reactive species, probably
CpMo(OH)(OOtBu)(h2-O2)Me, that transfers an O atom to the
alkene [15]. Both the methyl group and the Cp survive the oxidative
loss of the carbonyls as well as numerous catalytic cycles of
epoxidation.
These examples are sufficient to show that CO is one of the
easiest organometallic ligands to remove via oxidation. CO ligands
require back bonding for stable binding to a metal, but oxidation of
the metal greatly reduces the degree of back donation possible. This
effect also enhances the partial positive charge on the CO carbon
and so increases the tendency for nucleophilic attack at that carbon,
either by the solvent or the oxidant.
การแปล กรุณารอสักครู่..