Structural study of 3-oxypropyltin compounds

Abstract

The structures of (3-hydroxypropyl)iododiphenyltin 3 and 2,7-diiodo-2,7-diphenyl-1,6-dioxa-2,7-distannacyclodecane 6 have been determined by single-crystal X-ray diffraction. Compound 6, obtained by controlled thermolysis of 3, has a tricyclic structure, with a central Sn₂O₂ ring arising from transannular, Sn–O [i.e. Sn(2)–O(6) and Sn(7)–O(1)] interactions. The terminal rings in centrosymmetric 6 are in a transoid arrangement with respect to the central Sn₂O₂ ring, i.e. there is a stepped geometry. The tin atoms have trigonal-bipyramidal geometries being bonded in equatorial sites to two carbons and one oxygen [Sn–O′,i.e. Sn(2)–O(1) 2.060(7)Å] and in axial sites to iodine [Sn–I 2.776(1)Å] and to oxygen [Sn–O, i.e. Sn(2)–O(6) 2.268(7)Å]: I–Sn–O 161.7(2)°. In C₆H₆ and in chlorocarbon solutions, 6 exists as a 4.2 : 1 mixture of two isomers: the major one has the solid-state structure while the minor one has the terminal rings in an umbrella configuration, i.e. the terminal rings are cisoid with respect to the central Sn₂O₂ ring. Two sets of tin couplings to C(3)[C_β] and to C(4)[C_α] of each isomer were observed. Compound 3 exists as a chelate complex, with trigonal-bipyramidal tin: three equatorial C, with I[Sn–I 2.857(1)Å] and O[Sn–O 2.487(8)Å] axial [I–Sn–O 168.3(2)°]. Chelation persists in chlorocarbon solvents.