C2 and C1‐Symmetric Camphopyrazole Dioxomolybdenum(VI) Complexes catalyze the Epoxidation of Cyclic Olefins

• Published in: Zeitschrift für anorganische und allgemeine Chemie (1950) Vol. 649; no. 20
• Main Authors: Aguilera, Tania, Pastrán, Jesús, Llovera, Ligia, Linden, Anthony, Herrera, Alberto, Venuti, Doménico, Agrifoglio, Giuseppe, Dorta, Romano
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 16-10-2023
• Subjects: Alkenes; Camphor; Chemical analysis; Conversion; Coordination; Epoxidation; Hydrogen peroxide; Infrared spectroscopy; Ligands; NMR spectroscopy; Single crystals
• ISSN: 0044-2313; 1521-3749
• DOI: 10.1002/zaac.202300104

Dioxomolybdenum(VI) complexes (1‐6) were prepared in good yields (≥79 %) using enantiopure C2 and C1‐symmetric bidentate N,N‐ligands (L1‐L6) derived from (+)‐camphor. The ligands and complexes were characterized by NMR spectroscopy, IR, and elemental analysis. Single crystal X‐ray diffraction analyses of complexes 3, 4 and 6 confirmed the bidentate coordination modes of ligands L3, L4, and L6 and revealed distorted octahedral coordination geometries around the metal center. Complexes 3 and 6 form conformational isomers depending on the orientation of the substituents of the ligand aryl groups. Preliminary evaluation of the complexes as catalysts for the epoxidation of cyclohexene (81–93 % conversion) and cis‐cyclooctene (66–94 % conversion) with cumyl hydroperoxide and 35 % w/w aqueous hydrogen peroxide (39–73 %) demonstrated their activity for oxygen atom transfer reactions, opening the way for asymmetric epoxidations.