Multinuclear NMR Study of the Structure and Intramolecular Dynamics of (η2-Acetone phenylhydrazonato)tetrafluorooxotungsten(VI)

Using one- and two-dimensional techniques of 1H, 13C, 15N, and 19F NMR spectroscopy, it was proved that acetone phenylhydrazone (H-aph) acts as a two-center N,N-donor ligand in the complex [WOF4(aph)]-. As a result of the coordination to tungsten, the ligand conformation changes from E to Z, and at the same time the phenyl ring is turned out of the >NNC< plane. At low temperatures (−30 °C), the equatorial plane of the pentagonal-bipyramidal tungsten polyhedron comprises two donor nitrogen atoms of hydrazone and three fluoro ligands. At elevated temperatures, stereoisomeric interconversion caused by hindered intramolecular rotation of the aph- ligand occurs. The mechanism of this process was elucidated on the basis of the dynamic effects in 19F spectra and line-shape analysis of the trans-CH3 resonance in 13C spectra split due to direct “through-space” coupling with the proximate fluoro ligand.