The new binuclear oxothiolatorhenium(V) compound, Re2O2(mtp)(3), D-1, mtpH(
2) = 2-(mercaptomethyl)thiophenol. was found to activate molecular oxygen.
which has no precedent in oxorhenium catalysis. The kinetics and mechanism
of the oxidation of triaryl phosphines and methyl phenyl phosphines by O-2
were investigated. The reaction pathway inferred from the kinetic data invo
lves two Re(VII) intermediates, a peroxo and a mu -oxo species. The rate co
nstants were determined for both steps in this reaction. The mu -oxo Re(VII
) intermediate further reacts with a second phosphine forming more phosphin
e oxide as D-1 is recovered. This step is very rapid, and does not affect t
he kinetics. Other substrates, taken alone, such as sulfides and dienes, wh
ich coordinate to D-1 weakly, or do not coordinate, were not oxidized by mo
lecular oxygen. However, in the presence of a small amount of phosphine to
open up the sulfur bridge in D-1, then sulfides and dienes were also oxidiz
ed to sulfoxides and epoxides accordingly. The relative reactivities of the
substrates fall in the order: phosphines > sulfides > dienes. (C) 2001 Els
evier Science B.V. All rights reserved.