Oxidorhenium(V) Complexes with Oxazolinylmethoxido Ligands – Structure and Catalytic Epoxidation

Reaction of [ReOCl 3 (PPh 3 ) 2 ] with (4,5‐dihydrooxazol‐2‐yl)methanol and three methyl‐substituted derivatives thereof ( 2a – 2d ) in boiling acetone or tetrahydrofuran gave oxidorhenium(V) complexes of the type [ReOCl 2 (PPh 3 )( 2a – 2d )] ( 3a – 3d ) as blue crystalline materials in good yields. The complexes were characterized by 1 H, 13 C, 31 P NMR and IR spectroscopy, mass spectrometry, elemental analysis and single‐crystal X‐ray diffraction analysis. All the complexes showed distorted octahedral geometries and were found to contain only one oxazolyl ligand displacing one PPh 3 molecule and one chloride ion from the precursor complex [ReOCl 3 (PPh 3 ) 2 ]. The complexes were tested as catalysts for the epoxidation of cyclooctene with 3 equiv. of tert ‐butyl hydroperoxide (TBHP). Complex 3a containing (4,5‐dihydrooxazol‐2‐yl)methanol showed the highest yield of epoxide (79 %), whereas the complex with the tetramethyl‐substituted ligand 3d exhibited the lowest catalytic activity.