Solid-state conformations of medium-sized-ring phosphorus heterocycles: Preparation and x-ray crystal structure of a benzo-fused 1,3,2-dioxaphosphepane in a twist conformation

Abstract

The crystal and molecular structure of the benzo-fused seven-membered-ring phosphorus heterocycle, 2-phenyl-2-oxo-5,6-benzo-1,3,2-dioxaphosphepane, has been determined by single-crystal X-ray techniques. The compound crystallizes in the monoclinic space group P21/c with four molecules per unit cell of dimensions a = 13.312(1) A, b = 7.6132(8) A, c = 12.119(2) A, and β = 95.990(9)°. Full-matrix leastsquares refinement led to R = 4.4% and Rw = 5.9%. The conformation adopted by the 1,3,2-dioxaphosphepane ring is a twist with approximate C2 symmetry.