Synthesis and structure of new eight-membered Si–O–λ5σ4–P heterocycles

Abstract

The reaction of Bu₂^tSi(OLi)₂1 with PhPOCl₂ or of Ph₂Si(OLi)₂ with POCl₃ in a 1:1 molar ratio leads to the formation of the 1,3,3,7-tetraoxa-2,6-disila-4,8-λ⁵σ⁴-diphosphacyclooctanes 5 and 9, respectively. An X-ray structure analysis shows 5 to contain an eight-membered Si₂O₄P₂ ring in the chair conformation. The Si–O (1.65 Å) and P–O 1.57 Å bond lengths in the ring lie within the typical range; the terminal PO oxygen centres are in an axial position and oriented trans with respect to the central Si₂O₄ plane.