Mixed crystals containing the dioxo complex [[Ph3SiO]2VO2]- and novel pentacoordinated oxoperoxo complex [[Ph3SiO]2VO(O2)]-: X-ray crystal structure and assessment as oxidation catalysts.
[n-Bu4N][[Ph3SiO]2VO2] reacts with H2O2 to yield an oxoperoxo complex which crystallizes as a mixed-crystal compound, [P(C6H5)4][[(C6H5)3 SiO]2VO2]x[[(C6H5)3 SiO]2VO(O2)](1-x), 1(x = 0.57). It has been characterized by elemental analysis and spectroscopy (51V NMR, UV-visible and IR). The X-ray structure analysis reveals the presence of two interrelated anions: [[Ph3SiO]2VVO2]-, 1a, and [[Ph3SiO]2VVO(O2)]-, 1b with a cisoid geometry of the [VO(O2)]+ moiety. The two structures differ only slightly: anion 1a exhibits unusual tetrahedral coordination around the vanadium centre found in the precursor, whereas the geometry at the metal ion in 1b can be described as a trapezoidal pyramid. Steric constraints due to Ph3SiO- ligands and PPh4+ cations are responsible for this geometry. The reactivity of 1 in the C-C bond cleavage of 2-methylcyclohexanone under anaerobic conditions has been studied. The results suggest that peroxygen species are involved in the oxidative cleavage of C-C bonds of cycloalkanones.
Vennat
Maxence
M
Laboratoire des Systèmes Interfaciaux à l'Echelle Nanométrique, Université Pierre et Marie Curie/CNRS, case 196, 4 place Jussieu, 75252 Paris cedex 05, France. maxencevennat@yahoo.fr
Bregeault
Jean-Marie
JM
Herson
Patrick
P