Crystal structures of the benzo-15-crown-5 complexes di-isothiocyanato(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxa-cyclopehtadecin)-magnesium, -calcium–methanol (1/1), and -calcium hydrate

Abstract

The crystal structures of the three title complexes of ‘benzo-15-crown-5’ with Mg[NCS]₂, Ca[NCS]₂·MeOH, and Ca[NCS]₂·H₂O have been determined by direct methods from diffractometer data collected with molybdenum radiation. The magnesium complex crystallises in the orthorhombic space group Pbca with cell dimensions a= 16.399(3), b= 25.784(5), c= 9.230(3)Å, and z= 8. The structure has been refined to R 0.064 for 1 022 observations. The co-ordination of the cation is a pentagonal bipyramid with the nitrogen atoms of the anions in axial positions. The methanol complex with calcium isothiocyanate crystallises in the triclinic space group P, with cell dimensions a= 8.665(2), b= 11.155(2), c= 11.942(3)Åα= 95.49(1),β= 102.21 (2). γ= 102.47(2)°, and Z= 2. The final R factor is 0.081 for 4 244 observations. The calcium ion has irregular eight-co-ordination which includes the five ether oxygens, the two isothiocyanate nitrogens, and the oxygen atom of the methanol molecule. The analogous water complex crystallises in the monoclinic space group P2₁/c with cell dimensions a= 11.248(5), b= 12.929(7), c= 17.100(7)Å, β= 123.15(2)°, and Z= 4. The final R factor is 0.048 for 704 observations. The co-ordination of the cation is identical with that of the methanol complex with the water oxygen replacing the methanol oxygen atom. The same conformation for the crown ether is found in both the calcium complexes, indicating that intramolecular, not intermolecular or packing, forces decide the conformation.