Oxovanadium(V) complexes with tripodal bisphenolate and monophenolate ligands: Syntheses, structures and catalytic activities

Abstract The reactions between [VO(acac) 2 ] (acac – = acetylacetonate) and the tripodal amino bisphenols 6,6'-(((2-morpholinoethyl)azanediyl)bis(methylene))bis(2,4-di- tert -butylphenol) (H 2 L 1 ) and 6,6'-(((thiophen-2-ylmethyl)azanediyl)bis(methylene))bis(2,4-di- tert -butylphenol) (H 2 L 2 ) as well as the tetradentate amino phenol 2,2'-((3,5-di- tert -butyl-2-hydroxybenzyl)azanediyl)bis(ethan-1-ol) (H 3 L 3 ) afford the complexes [VO( L 1 )(OMe)] ( 1 ), [VO( L 2 )(acac)] ( 2 ) and [VO( L 3 )] ( 3 ), correspondingly. Complexes 1 and 3 can also be prepared using VOSO 4 ·xH 2 O or [VO(OPr) 3 ] as vanadium precursors. When [VO(acac) 2 ] or VOSO 4 ·xH 2 O is used, mononuclear oxovanadium(V) complexes are formed upon oxidation of the metal precursor. Single crystal X-ray structure analysis show that complexes 1 and 2 have distorted octahedral coordination spheres, in which the amino bisphenolate coordinates in a tetradentate or tridentate manner, respectively, and the coordination spheres are completed by methoxy or acetylacetonato ligands. Complex 3 has a slightly distorted trigonal bipyramidal geometry with an NO 4 coordination environment. All three complexes can catalyze epoxidation of cis -cyclooctene at 50 °C with tert -butyl hydroperoxide (TBHP) or H 2 O 2 as an oxygen source, and sulfoxidation of thioanisole or methyl- p -tolylsulfide proceeds at 25 °C using the same oxidants.