STRUCTURE OF TETRAAQUACOPPER(II) CHLORATE AT 296-K AND 223-K

[Cu(H2O)4](ClO3)2, M(r) = 302.51, orthorhombic, Pbca, lambda-(Mo K-alpha-BAR) = 0.71069 angstrom, Z = 4, F(000) = 604; T = 296 K, a = 12.924 (3), b = 9.502 (2), c = 7.233 (1) angstrom, V = 888.3 (3) angstrom 3, D(x) = 2.26 g cm-3, mu = 31.04 cm-1, R = 0.041 for 1174 unique reflections with I > sigma(I); T = 223 K, a = 12.853 (2), b = 9.492 (2), c = 7.216 (2) angstrom, V = 880.4 (3) angstrom 3, D(x) = 2.28 g cm-3, mu = 31.28 cm-1, R = 0.033 for 1279 unique reflections with I > sigma(I). The single type of copper ion is octahedrally coordinated by four water oxygens and two chlorate ion oxygens; the complex is characterized by three distinct pairs of Cu-O distances (which we have previously described as '2 + 2 + 2' coordination), one of which is substantially larger than the remaining two. The nominal 90-degrees O-Cu-O angles of the complex differ from that value by at most +/- 1.8-degrees. The observed structure of the complex is typical for copper(II) and is consistent with the Jahn-Teller effect. The single type of chlorate ion shows the expected trigonal pyramidal geometry, with average Cl-O bond lengths 1.485 (13) and 1.490 (11) angstrom and average O-Cl-O bond angles 106.8 (13) and 106.8 (13)-degrees for 296 and 223 K, respectively. Location and refinement of the four inequivalent H atoms of the two water molecules permitted detailed analysis of the hydrogen bonding which occurs almost solely between the water hydrogens and chlorate oxygens. Rigid-body analysis showed that while the chlorate ion did not conform to such behavior, the copper ion and the water oxygens (but not the chlorate oxygens) of the octahedral complex did; correction of the relevant bond lengths for the rigid-body effects has been applied. This study is apparently the first which describes the structure of a tetraaquacopper(II) complex.