Crystal and molecular structure of 5-t-butyl-2-methyl-2-oxo-1,3,2-dioxaphosphorinan (C8H17PO3)

Abstract

The crystal structure of 5-t-butyl-2-methyl-2-oxo-1,3,2-dioxaphosphorinan (C₈H₁₇PO₃) has been determined by three-dimensional X-ray analysis. The crystals are orthorhombic, space group Pbca, with Z= 8 in a unit cell of dimensions a= 11·371, b= 12·557, and c= 14·608 Å. Intensities of 971 reflections were measured on a diffractometer. The structure was solved by Patterson and Fourier methods and refined to R 6·9% for 529 observed reflections. The six-membered ring is in a distorted chair form with the t-butyl group cis to the methyl group at C(11). The bond angles around phosphorus range from 104·4–113·2°. Some bond distances are: PO 1·48, P–O 1·56 and 1·58, and C–C 1·47–1·59 Å; the mean σ is 0·02 Å for bond distances and 0·8° for bond angles. Comparisons with other 1,3,2-dioxaphosphorinans having oxygen or bromine substituted axially at phosphorus suggest a dependence of angular geometry on the size of the axial substituent.