The crystal structure of 1,4,7,14,17,20,28,35-octaoxa[2.23,29][7.718,34]-orthocyclophane and its multihydrated complex with potassium chloride

Abstract

Crystal structures of a bridged crown ether (I), systematically named in the title, and its complex with potassium chloride (II) have been determined by X-ray diffraction. Observations were collected on a four-circle diffractometer. Compound (I) is monoclinic, a= 11.539(2), b= 9.558(3), c= 22.802(7)Å, β= 98.19(2)° with space group P2₁/c. Compound (II) crystallises with eight complex cations [K(I)]⁺, eight chloride ions, and 44 water molecules in a monoclinic unit cell, a= 22.578(6), b= 17.162(5), c= 16.742(5)Å, β= 99.48(2)° and space group I2/c. Full matrix refinement of (I) led to an R value of 0.066 for 1 775 observed reflections. The molecule has no symmetry, the conformation of the portion from O(1) to O(7) is unusual, unfavourable torsion angles may be correlated with inter-, but not with intra-molecular O ⋯ HC contacts. Part of the structure exhibits disorder, one oxygen atom O(28) was allowed partial occupancy of two sites, and the benzene ring to which it is attached was allowed anisotropic vibration parameters as were all the oxygen atoms. The structure of (II) consists of complex cations which have a non-crystallographic plane of symmetry. Co-ordination about the potassium ion approximates to an end-capped trigonal prism, K–O distances to the capping atoms (CH₂–O–CH₂) average 2.687 Å, and those for the other atoms average 2.733 Å. There are no interactions between the anions or water molecules and the potassium ions, or the eight oxygen atoms of the ligand. The cations are packed, with contacts of normal van der Waals distances, to form channels parallel to the c axis of the crystal. In these channels chloride ions, mainly disordered over two sites, and water molecules, also disordered, form networks which cannot be uniquely determined. Full matrix refinement gave an R value of 0.104 for 2 138 observed reflections. In this the potassium ion and the carbon atoms of one benzene ring were allowed anisotropic vibration; the other atoms of the cation were allowed isotropic vibration parameters while the disordered atoms were all assumed to have mean square isotropic vibrations of 0.25 Ų and their occupation numbers were treated as parameters.