Abstract
Di(2-naphthyl) ditelluride (1), synthesized by reaction of 2-chloronaphthalene with alkali metal ditelluride reagents in dipolar aprotic solvents, crystallizes in two polymorphic modifi- cations. Single-crystal X-ray structure determinations show these to be conformational polymorphs. Polymorph la is monclinic, space group P2i/c, a = 8.406(3), b = 6.304(2), c = 32.323(9) Á, ß = 99.92(3)°, V = 1687.2 A3, and Z = 4. Polymorph lb is also monoclinic, space group C2/c, a = 36.654(11), b = 7.840(2), c = 12.084(4) A, ß = 104.56(3)°, V = 3361.9 A3, and Z = 8. Polymorph la has a C-Te-Te-C torsion angle of 105.2° and relatively long Te—Te contacts (4.13, 4.41 A), while polymorph lb has a C-Te-Te-C angle of 78.6° and short intermolecular Te—Te contacts of 3.708 and 4.002 A. Polymorphs la and lb have also been characterized by differential scanning calorimetry and by infrared, Raman, and solid-state electronic spectroscopy. Raman shifted lines at 188 and 182 cm-1 in la and lb, respectively, are assigned to the ditelluride stretching mode. Polymorph lb exhibits a shoulder near 510 nm in its solid-state electronic spectrum. This feature is not observed either in solution spectra or in the spectrum of solid la. It is likely that the shoulder is associated with an extended electronic structure which arises from a continuous set of short Te—Te nonbonded contacts.