Crystal structures of complexes between alkali-metal salts and cylic polyethers. Part 11. Complexes formed between 2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin (benzo-15-crown-5) and sodium perchlorate (1 : 1), sodium perchlorate (2 : 1), and sodium tetraphenylborate (2 : 1)

Abstract

The crystal structures of the three title compounds of ‘benzo-15-crown-5’ with Na[ClO₄] in 1 : 1 and 2 : 1 ratio and with Na[BPh₄] in 2 : 1 ratio have been determined from diffractometer data collected with molybdenum radiation. The 1 : 1 complex with Na[ClO₄] crystallises in the monoclinic space group P2₁/c with cell dimensions a= 8.806(3), b= 8.310(10), c= 24.148(7)Å, β= 99.16(1)°, and Z= 4. The final R factor is 0.075 for 1 737 observations. The cation is irregularly co-ordinated to five oxygen atoms from the crown ligand and two from the anion. The conformation of the ether is similar to that found in the NaI·H₂O complex. The 2 : 1 complex with Na[ClO₄] forms crystals with the tetragonal space group P4/n, which are isomorphous with the Kl complex, with a= 17.786(7), c= 9.869(5)Å, and Z= 4. The sturcture has been refined R= 0.121 for 1 053 observations, due to disorder problems in the atomic positions. The complex has a centrosymmetric sandwich structure and two conformers are present in proportion 0.523 : 0.477, the first being similar to that found in the free ligand, the second, new. The co-ordination number of the cation is not clear, due to a wide spread in the range of Na–O distances. The 2 : 1 complex with Na[BPh₄] is monoclinic, space group P2₁/c with a= 12.497(3), b= 19.450(3), c= 19.896(4)Å, β= 94.76(2)°, and Z= 4. The final R factor was 0.080 for 1 258 observations. A different sandwich structure is present in these crystals, with no symmetry, and again the co-ordination number of the cation is not clear. The conformations of the two independent ether molecules are similar to each other and to that found in the free-ligand crystals.