Preparation of hexacoordinated tris(bidentate) phosphorus compounds with 1,3,2-dioxaphosphorinane rings. NMR and X-ray crystallographic studies of their conformation

A series of new unstable tris(bidentate) hexacoordinated phosphorus compoun ds 1 with 1,3,2-dioxaphosphorinane rings was prepared and studied by NMR an d X-ray crystallography. The X-ray crystal structures showed that the 1,3,2 -dioxaphosphorinane ring adopts different conformations depending on the nu mber and size of substituents at the carbon atom C14. Substituents are depl oyed around the phosphorus atom in a slightly deformed octahedral structure . Deviations in bond lengths around the phosphorus atom depend on the chara cter of the bonds and the distribution of the negative charge. H-1 and C-13 NMR measurements showed that in solution the flexibility of 1,3,2-dioxapho sphorinane ring depends on the size of substituents at the carbon C14.