Synthesis and structure of new eight-membered Si–O–λ5σ4–P heterocycles
Abstract
The reaction of Bu2tSi(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.