SUBSTITUTED N,N-CHELATE LIGANDS - APPLICA TIONS IN MOLYBDENUM-CATALYZED EPOXIDATION OF OLEFINS

Oxodiperoxomolybdenum complexes 4 of substituted 2-[3(5)-pyrazolyl]pyr idines (2a-g) were synthesized in order to control the solubility of t hese complexes in organic solvents. Alkyl side chains (butyl, octyl, o ctadecyl) increase the solubility of the complexes and enable spectros copic investigations in solution. Due to the symmetry of the ligands t he peroxo complexes 4 appear in two isomeric forms, with the terminal oxo ligand in the trans position either to pyridine or to pyrazole. Th e latter isomer of (C(5)H(4)NC(3)H(2)N(2)CH(2)COOEt)MoO(O-2)(2) (4f) w as characterized by an X-ray structure analysis. The alkyl-substituted peroxo complexes are active catalysts for the epoxidation of olefins with tert-butyl hydroperoxide.