MOLECULAR-STRUCTURE AND MAGNETIC-PROPERTIES OF THE CHLORO-BRIDGED DIMER CHLORO[HYDROTRIS(1-PYRAZOLYL)BORATO]COPPER(II) - OBSERVATION OF A FERROMAGNETIC GROUND-STATE

The complexes {CuCl[HB(l-pz)3]}2 and CoCl[HB(1-pz)3] have been prepared. The crystal structure of the copper(II) compound has been solved and the magnetic susceptibility measured. The compound belongs to the P2jn space group with [FORMULA OMMITED] The centrosymmetric structure has symmetric chloro bridges between the coppers leading to a distorted five-coordinate geometry about these metal centers. The geometry about each copper approximates that of a distorted square pyramid. The bridging chlorides and two ligand nitrogen atoms form the base of the pyramid, and the third ligand nitrogen occupies the axial site. The planar Cu2Cl2 bridge has Cu-Cl distances of 2.306 (2) and 2.316 (2) Å and a Cu-Cl-Cu angle of 94.51 (7)°. The electronic and EPR spectra are compatible with such a structure. The susceptibility data down to a temperature of 2 K show the presence of a ferromagnetically coupled ground state (2J/k=48.6°) for the dimer. The data have been fitted in accord with a model of He senberg dimers with Ising-like coupling to adjacent dimers. The complex CoCl[HB(l-pz)3] shows an electronic spectrum in solution suggestive of a pseudotetrahedral geometry about Co(II). © 1979, American Chemical Society. All rights reserved.