Synthesis and Relation Between Magnetism and Structure of a Trinuclear Copper(II) Hydroxo Complex [Cu₃OHL₃(ClO₄)]ClO₄ and a Hexanuclear Copper(II) Oxo Complex [Cu₃OL′₃(ClO₄)]₂ (LH = 3-(phenylimino)butanone 2-oxime, L′H = 1,2-diphenyl-2-(methylimino)ethanone 1-oxime)

The synthesis, structure, and properties of the title complexes are described. The cation of the complex [Cu3OHL3(ClO4)]ClO4 is trinuclear with a Cu3OH skeleton which has one oxime N-O bridge between each pair of copper atoms. By contrast, previous studies had identified Cu3O species. The existence of the Cu3OH fragment is confirmed by a pseudotetrahedral oxygen environment and by detection of the OH hydrogen atom and the extra perchlorate required by stoichiometry. [Cu3OL′3(ClO4)]2 is a centrosymmetric hexanuclear molecule containing two equivalent Cu3O units, the central oxygens of which are bonded to a copper from the other Cu3O unit via a relatively weak Cu-O bond (2.334 (3) Å). The central oxygens of the Cu3O groups are very flattened tetrahedra, whose apices point along the Cu-O bonds linking the two Cu3O units. The Cu3O units in [Cu3OL′3(ClO4)]2 have stronger Cu-O bonds (av. 1.868 Å) than those in the Cu3OH units of [Cu3OHL3(ClO4)]ClO4 (1.964 Å), in keeping with the greater negative charge on the central oxygen atom. [Cu3OH-L3(ClO4)]ClO4 exhibits relatively strong intramolecular antiferromagnetic interactions (J = -122 cm-1). At very low temperature (∼5 K), a weak interionic interaction is evident so that the magnetic moment falls below that expected for one unpaired electron. In [Cu3OL′3(ClO4)]2 the antiferromagnetic interaction within the Cu3O units is far stronger, so that only a single unpaired electron per Cu3O unit is observed even at high temperatures. At low temperatures a further (weaker) interaction is observed, presumably between the two Cu3O units of the hexanuclear complex to promote a further decrease in magnetic moment. Crystal data for [Cu3OHL3(ClO4)]ClO4: space group P21/n, Z = 4, a = 15.630 (8) Å, b = 14.354 (3) Å, c = 17.255 (4) Å, β = 93.39 (5)°, V = 3864 Å3, R = 6.4% for 1840 reflections. Crystal data for [Cu3OL′3(ClO4)]2: space group P21/n, Z = 2, a = 14.063 (6) Å, b = 19.449 (5) Å, c = 17.131 (9) Å, β = 97.62 (4)°, V = 4644 Å3, R = 5.0% for 4591 reflections. © 1981 American Chemical Society