X-RAY STRUCTURAL INVESTIGATION ON DIISOPROPYL PHTHALIDE-3-PHOSPHONATE

The crystal structure of diisopropyl phthalide-3-phosphonate has been determined by X-ray crystallography. The cyclic part of the molecule i s essentially planar. Of the two -OCH(CH3)(2) groups, one is directed outwards with respect to the ring system, while the other points at on e of the carbon atoms of the five-membered ring. A pronounced differen ce occurs between the two C-O single bonds of the hetero-ring; this ca n be attributed to the 'background delocalization' phenomenon. Of the two angles based on the C=O double bond, the O=C-O angle is much small er than the respective O=C-C angle. Two enantiomeric molecules related by a centre of symmetry form cyclic dimers linked by two intermolecul ar hydrogen bonds. The packing arrangement reveals stacking of the pla nar skeletons of the molecules along the Z axis. The crystal data are: C14H19O5P, triclinic, P (1) over bar, a = 8.067(3) Angstrom, b = 9.27 8(3) Angstrom, c = 11.540(3) Angstrom, alpha = 109.14(3)degrees, beta = 105.73(3)degrees, gamma = 97.66(3)degrees, V = 761.6(5) Angstrom(3), Z = 2. (C) 1998 Elsevier Science B.V.