Crystal and molecular structure of 2,2,3,4,4-pentamethyl-1-phenylphosphetan 1-oxide (C14H21PO)

Abstract

The crystals of 2,2,3,4,4-pentamethyl-1-phenylphosphetan 1-oxide are orthorhombic, space group Pca2₁, with Z= 8 in a unit cell of dimensions a= 12·335, b= 15·913, and c= 14·187 Å. There are two crystallographically unrelated molecules in the asymmetric unit. Intensities of 1514 independent reflections were measured on a diffractometer, and 993 reflections were used for the subsequent refinement by block-diagonal least-squares methods to R 6·8%. The structure was solved by locating two independent phosphorus atoms from a three-dimensional Patterson map and subsequent Fourier syntheses. The bond angles around phosphorus atoms are considerably distorted from tetrahedral, ranging from 81·9–122·6° in one case and 81·8–121·1° in the other, the small angles being those in the heterocyclic rings. The four-membered rings are not planar in either molecule and are very strained. In both molecules the methyl group at C(3) is trans to the phenyl ring.