An X-ray crystallographic investigation of the structures of pyrazine adducts of diphenyltin dichloride and dimethyltin dichloride

Abstract

Reaction of SnPh₂Cl₂ with pyrazine (pyz) leads exclusively to the formation of an adduct having the bulk composition SnPh₂Cl₂·0.75pyz. It has a structure composed of layers in which zig-zag polymeric chains, (SnPh₂Cl₂·pyz)_n, with six-co-ordinate tin, alternate with layers containing non-interacting molecules of (SnPh₂Cl₂)₂·pyz, with five-co-ordinate tin. The Sn–N bond lengths are abnormally long; each tin atom tin atom in the polymeric chains has Sn–N bond lengths of 2.961(10) and 2.783(10)Å, and the Sn–N bond length in (SnPh₂Cl₂)₂·pyz is 2.683(11)Å. Mössbauer spectroscopy does not identify the presence of the two tin sites in the solid whereas ¹¹⁹Sn n.m.r. does. X-Ray crystallographic details are: space group Pbam(orthorhombic), a= 14.935(2), b= 13.409(3), c= 14.959(3)Å, Z= 8(Sn), R= 0.047 (R′= 0.056) for 1 478 observed reflections with I > 3σ(I). Reaction of SnMe₂Cl₂ with pyrazine leads exclusively to formation of the adduct (SnMe₂Cl₂)₂·pyz; the distannoxane (SnMe₂Cl)₂O is also formed if solutions are not protected from the atmosphere. The adduct has a chain polymeric structure with six-co-ordinate tin atoms alternatively linked by chloride ions and pyrazine molecules. The Sn–N bond length [2.746(6)Å] is abnormally long. The polymeric chains pack into well defined planes, with chains in alternate planes propagating in orthogonal directions. Crystallographic details are: space group P2₁/n(monoclinic), a= 6.855(1), b= 10.344(2), c= 12.014(3)Å, β= 92.590(7)°, Z= 2, R= 0.03 (R′= 0.033) for 727 observed reflections with I > 3σ(I).