text: Compounds with disphenoidal (see-saw) geometry have two types of ligands: axial and equatorial. The axial pair lie along a common bond axis so that are related by a bond angle of 180°. The equatorial pair of ligands is situated in a plane orthogonal to the axis of the axial pair. Typically the bond distance to the axial ligands is longer than to the equatorial ligands. The ideal angle between the axial ligands and the equatorial ligands is 90°; whereas the ideal angle between the two equatorial ligands themselves is 120°.
  Disphenoidal molecules, like trigonal bipyramidal ones, are subject to Berry pseudorotation in which the axial ligands move to equatorial positions and vice versa. This exchange of positions results in similar time-averaged environments for the two types of ligands. Thus, the F NMR spectrum of SF (like that of PF) consists of single resonance near room temperature. The four atoms in motion act as a lever about the central atom; for example, the four fluorine atoms of sulfur tetrafluoride rotate around the sulfur atom.