Crystal structure and magnetic properties of a unique copper(II) compound, octakis([μ-dichloroacetato- O, O′)bis(dichloroacetato- O)hexakis-[μ 3-(2-dimethylaminoethanolato)] di-μ 3-hydroxo-nonacopper(II)

Abstract

The synthesis, characterization, X-ray structure, and magnetic properties are reported for the title compound Cu 9(CHCl 2 COO) 10(C 4H 10NO) 6(OH) 2. The compound crystallizes in the monoclinic space group P2/ n. Cell dimensions are a=14.835(3), b= 14.205(4), c=20.887(5) Å, β=97.46(2)°. The structure was solved by direct and Fourier methods and refined by least-squares techniques to a conventional R value of 0.059 for 3006 reflections. The crystal structure consists of discrete nonameric complex molecules which possess a twofold rotation axis passing through a copper atom. The nine copper atoms in the molecule are bridged together by carboxylate groups and triply bridging ethanolato oxygen and triply bridging hydroxo oxygen atoms. The aminoethanolato ligands chelate through the amino nitrogen (terminal) and the alcohol oxygen (triply bridging). One of the five independent carboxylato groups is unidentate; the other four bridge a pair of copper atoms each, and one of the four forms in addition a monoatomic unsymmetrical bridge to a third copper atom. The Cu1, Cu2, Cu3 and triply bridging hydroxo oxygen atoms form a trigonal pyramid with CuO bonds of 1.941, 1.964 and 2.149 Å. In a similar arrangement one of the three independent ethanolato oxygen bridges Cu2, Cu3 and Cu4 with CuO bonds of 1.996, 2.111 and 1.977 Å. The CuO distances of the other ethanolato oxygen atoms are 1.930, 2.645, 1.981 Å for Cu3, Cu4, Cu5 and 2.380, 1.963, 1.904 Å for Cu2, Cu4, Cu5. The copper coordination number is either five (Cu3 and Cu5) or six (Cu1, Cu2, Cu4), the coordination polyhedra being square-pyramidal or octahedral, respectively. The coordination sphere of the Cu1 atom lying on the twofold rotation axis is very unusual in that the equatorial CuO bonds (2.107 and 2.207 Å) are longer than the axial bonds (1.941 Å).