The dioxomolybdenum and dioxotungsten complexes [MoO 2L 1] (1-Mo) and [WO 2L 1] (2-W), supported by a diamine bis(phenolate) ligand (L 1 = Me 2NCH 2CH 2N(CH 2-2-O-3,5-C 6H 2 tBu 2) 2) were prepared from MoO 2Cl 2 and WO 2Cl 2(dme) in good yields. The solid-state structures of both compounds obtained by single crystal X-ray diffraction reveal distorted octahedral geometries around the metals with cis terminal oxo ligands. Their performance in the catalytic epoxidation of cis-cyclooctene using H 2O 2 and TBHP as oxidants was evaluated. 2-W displays high activity with H 2O 2 as terminal oxidant, achieving 84% conversion in 6 h (TOF = 1400 mol sub mol cat -1 h -1), while its molybdenum counterpart 1-Mo was inactive in the same conditions. Using TBHP as oxidant the opposite trend was observed and 1-Mo attained 93% conversion in 6 h (TOF = 1550 mol sub mol cat -1 h -1). The Oxovanadium complexes [VOL 1Cl] (3-V), [VOL 2Cl] (4-V, L 2 = Me 2NCH 2CH(CH 3)N(CH 2-2-O-3,5-C 6H 2 tBu 2) 2) and [(VOL 1) 2(μ-O)] (5-V) were also tested as catalysts in the epoxidation of cis-cyclooctene. The three compounds display high activity when the epoxidation reaction is performed using TBHP as oxidant. Using H 2O 2, 3-V and 4-V are moderately active while 5-V is inactive.
- Diamine bis(phenolate) complexes