New possibilities of NMR in mechanistic studies of homogeneous and heterogeneous catalysis

Abstract

Results are presented that demonstrate new possibilities provided by modern Fourier-transform NMR spectrometers in the mechanistic studies of both homogeneous and heterogeneous catalysis. As particular examples, are discussed: (1) in situ characterization of the intermediate alkylperoxo complexes of Mo(VI), V(V) and Co(III) in the course of homogeneous epoxidation of cyclohexene and oxidation of cyclohexane from simultaneously recorded 95Mo, 51V or 59Co NMR spectra and 1H, 17O NMR spectra. (2) in situ characterization of reaction intermediates from the rates of paramagnetic 1H and 13C nuclear relaxation in the course of homogeneous decomposition of cumyl hydroperoxide in the presence of μ 3-oxotricobalt (II,III,III) acetate and μ 3-oxotriruthenium (III) acetate and of propylene oxidation into propylene glycol by CuCl 2-I 2 catalytic system. (3) Characterization with 51V NMR of a family of V(V) sites in supported vanadium catalysts. (4) Elucidation from a combination of 13C CP/MAS NMR, 13C 2D/MAS NMR and 2H NMR of butyl silyl ether intermediates in the course of dehydration of butanols on H-ZSM-5 zeolite.