The n.m.r. of paramagnetic complexes of vanadyl acetylacetonate with organic phosphites and hydroperoxides

✍ Scribed by D. G. Pobedimskii; Sh. A. Nasybullin; P. A. Kirpichnikov; R. B. Svitych; O. P. Yablonskii; A. L. Buchachenko

• Book ID: 102525365
• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: English
• Weight: 335 KB
• Volume: 9
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270090202

✦ Synopsis

Abstract

The vanadium IV ion in vanadyl acetylacetonate (V^IV^) forms labile paramagnetic complexes with organic phosphites in the first coordination sphere. The enthalpy of complex formation between V^IV^ and triphenyl phosphite was 2.6 kcal mol^−1^. Complex formation enthalpies Δ__H__ and the activation energies E of ligand (hydroperoxide) escape from the metal ion sphere were determined from the temperature dependence of paramagnetic broadening of the n.m.r. lines of hydroperoxides in the presence of vanadyl acetylacetonate. At low temperatures the phosphite sharply weakens the bond between the metal ion and hydroperoxide in the second coordination sphere (Δ__H__ decreases fivefold). Taken in excess, phosphite displaces the hydroperoxide molecules from the coordination sphere of the V^IV^ ion and thus blocks it. The observed n.m.r. characteristics of the paramagnetic complexes explain, on the model level, the kinetic regularities of the reaction of hydroperoxides with phosphite catalysed by transient metal ions.