Formation and X-ray analysis of the supramolecular system obtained by the complexation of (E)-9,10-diphenyl-2,5,8,11,14,17-hexaoxaoctadec-9-ene with sodium thiocyanate. A new coordination type for SCN–

Abstract

The synthesis and X-ray structure of (E)-9,10-diphenyl-2,5,8,11,14,17-hexaoxaoctadec-9-ene 1 and that of its complex with sodium thiocyanate are described. The free ligand is centrosymmetric with the phenyl ring twisted out of the ethylenic plane by 39° and a rather extended conformation of the polyether chain. The complex of 1 with NaSCN has been obtained; its solid state structure is quite unique. There are two (1A and 1B) independent supramolecular systems 1·2NaSCN·2H₂O with similar geometries in the asymmetric part of the unit cell. Each system is arranged in infinite independent chains with ‘organic’ and ‘inorganic’ parts that alternate. In one of these systems (1B), disorder of the CC double bond is observed. In each complex unit, the polyether side arms in the trans position are coordinated each to a different Na⁺. The conformation of the polyether chain is (ag^±a)(g^∓g^∓a) in three cases but the same as in the free ligand (ag^±a)(ag^±g^±) in the fourth. Both Na⁺ cations have a sixfold octahedral coordination: two O of the polyether, three N of the SCN^– and one O of a water molecule are the ligating atoms of Na(1) while one N of an anion is replaced by a second water molecule for Na(2). In this complex, one observes a bridging of one SCN^– between two cations and even between three cations for the second SCN^–; this last kind of threefold bridging has never been reported before for the thiocyanate anion.