Syntheses and solid state structures of cyclic diynes with two chalcogen centres ? a competition between weak interactions

In this paper we report the synthesis of cyclic diynes of the general formula mX2n. The letters m and n indicate the lengths of chains between two C triple bond C-X units where X indicates S, Se, or Te. The lengths of the bridges vary between m=4-8 and n=2-6. Structural investigations by means of X-ray diffraction reveal for most systems a chair-like conformation in the solid state. For 5S(2)2, 5S(2)3, 7S(2)5, 5Se(2)2 and 5Te(2)3 tubular structures were encountered. These structures can be traced back to weak XX or weak C-Hpi interactions.