De. Devos et T. Bein, HIGHLY SELECTIVE OLEFIN EPOXIDATION WITH MANGANESE TRIAZACYCLONONANE COMPLEXES - IMPACT OF LIGAND SUBSTITUTION, Journal of organometallic chemistry, 520(1-2), 1996, pp. 195-200
Manganese complexes of 1,4,7-triazacyclononane with different substitu
ents catalyze the selective epoxidation of a large number of olefins t
o epoxides with H2O2. The activities of complexes with methyl (L(1)),
2-hydroxybutyl (L(2)) and acetato (L(3)) substituents are compared, Th
e effects of solvent and temperature on the epoxide yield are very dif
ferent for the three complexes. It is proposed that these differences
are related to the binding of the pendant arms in Mn-L(2) and Mn-L(3)
complexes. In general, acetone or methanol are preferred solvents, Var
iations of stereoretention are also observed: with Mn-L(1) in acetone,
isomer scrambling occurs, while with Mn-L(1) in methanol, the epoxida
tion is almost stereospecific. UV-visible and electron spin resonance
spectroscopy are used to characterize the state of manganese under oxi
dizing conditions.