THE CRYSTAL-STRUCTURE OF THE CU4O4-HETEROCUBANE COPPER(II) COMPLEX [CU(OCH2CH2N(C4H9)(2))NCO](4) AT 200 K

The structure of kis-N,N-dibutylaminoethanolatoisocyanatocopper(II) wa s determined from single crystal X-ray data at 200 K, since a phase tr ansition at 235 K was proposed from an unsteadiness in the temperature dependence of the magnetic susceptibility data as well as from some d isagreement concerning a very reliable magnetostructural correlation. The structure analysis confirmed the phase transition magnetically obs erved. Below 235 K, eight tetrameric molecules are arranged in a tricl inic unit cell with the dimensions a = 24.052(4) Angstrom, b = 13.014( 2) Angstrom, c = 39.249(4) Angstrom, alpha = 72.26(1)degrees, beta = 1 04.16(1)degrees, gamma = 107.30(1)degrees, space group B (1) over bar, which is of fourfold volume as compared to the structure at 295 K (a = 2a', c = 2c'). The two crystallographically different molecules show distinct differences mainly concerning the central Cu4O4-heterocubane moieties. For the first time, an arrangement is observed in which, ac cording to the Mergehenn nomenclature, type-I and transition type Cu4O 4-molecules coexist.