Using one- and two-dimensional techniques of H-1, C-13, N-15 and F-19 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 degrees 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 F-19 spectra and line-shape analysis of the trans-CH3 resonance in C-13 spectra split due to direct "through-space" coupling with the proximate fluoro ligand.