Reduction of nitro- and nitroso-compounds by tervalent phosphorus reagents. Part XIV. X-Ray crystallographic determination of the structures of 3-(2,6-dimethylphenyl)-2,3-dihydro-2,2,2-trimethoxy-1,3,2-benzoxazaphosph(V)ole and its 2-hydroxy-2-oxo-analogue

Abstract

3-(2,6-Dimethylphenyl)-2,3-dihydro-2,2,2-trimethoxy-1,3,2-benzoxazaphosph(V)ole (1) is a trigonal bipyramidal phosphorus compound with only slight deviation from ideal geometry. The five-membered oxazaphosphole ring is planar and occupies an apical-equatorial site with apical oxygen and equatorial nitrogen, the latter being sp²-hybridised. The pendant N-(2,6-dimethylphenyl) ring is almost completely orthogonal to the second benzene ring. The crystals are monoclinic with a= 6.93(2), b= 20.26(4), c= 12.13(8)Å, β= 96.7(4)°, space group P2₁/n.

The 2-hydroxy-2-oxo-analogue (2) also exhibits orthogonality of the N-(2,6-dimethylphenyl) ring. The oxazaphosphole ring is almost planar and exhibits distorted tetrahedral geometry about phosphorus (O–P–N angle 96.3°). The crystals are monoclinic with a= 10.786(5), b= 13.222(5), c= 9.634(4)Å, β= 90.0(1)°, space group P2₁/c.