FOLDING ONTO COPPER(II) OF A FLEXIBLE BIS-CHELATING 4-ACYL-PYRAZOL-5-OLATE

The structure of {1,10-bis[5-(hydroxy-kappa ecane-1,10-dionato(2-)-kap pa(2)O(1,10}-copper(II), [Cu(C30H32N4O4)], has been determined. It con sists of two types of [Cu{L-(CH2)(8)-L}] mononuclear unit (HL = 5-hydr oxy-3-methyl-1-phenyl-4-pyrazoloyl functional group), characterized by different conformations of the polymethylene chain. Both molecules co ntain a Cu atom in an almost square-planar environment of O atoms [1.9 07(8) < Cu-O < 1.939(8)Angstrom]. All acylpyrazolonate moieties are pl anar within experimental error. The phenyl rings make angles in the ra nge 2-28 degrees with the corresponding pyrazole planes. In the first type of [Cu{L-(CH2)(8)-L}] moiety (1), the two chelating subunits and the metal plane adopt a stepped conformation, whereas in the second [C u({L-(CH2)(8)-L}] moiety (2), one of the two chelating subunits and th e metal plane are coplanar. The mononuclear units form centrosymmetric dimers (1,1') and (2,2'), in which the Cu atoms may be viewed as five -coordinate [Cu...O' = 2.546(8) and 2.463(9)Angstrom, respectively, in (1,1') and 2,2')].