Rhenium(V) oxo complexes with acetylacetone derived schiff bases: Structure and catalytic epoxidation

Abstract

Substitution reactions of rhenium(V) oxo precursors [ReOC13(PPh3)21 or [NBU4][ReOC141 with the bidentate acetylacetone-d e rived ketoamine ligands APOH = 4-anilino-3-penten-2-one, DPOH = 4-[2,6-dimethylanilino]-3penten-2-one, and MTPOH = 4-[2-(methylthio)anilinol-3-penten-2-one gave the complexes [ReO(APO)CI2(PPh3)] (1), [ReO(DPO)C]2(PPh3)] (2), and [NBU4][ReOLCI31 (3, L = APO; 4, L = DPO; 5, L = MTPO), respectively. All complexes exhibit only one ketoamino chelate, independent of the amount of ligand added to the rhenium precursors. The complexes were characterized by 1H and 13C NMR spectroscopy. X-ray crystal structures of the complexes 1, 2, 4, and 5, including that of MTPOH, were determined, revealing the trans position of the two oxygen atoms and the trans-CI,Cl conformation in 1 and 2, in contrast to most other rhenium complexes of this type where the cis-CI,Cl conformation is observed. Coordination of the potentially tridentate ligand MTPOH in 5 is bidentate with a dangling thioether substituent. Compound 2 shows catalytic activity in the oxidation of cis-cyclooctene with tertbuty1hydroperoxide.