STRUCTURE AND PROPERTIES OF LANTHANIDE CATALYSTS - THE CRYSTAL AND MOLECULAR-STRUCTURE OF SMBR3.4IPR(OH)

The crystal of the title compound is monoclinic (space group C2/c), with a = 22.067(17), b = 10.111(10), c = 16.886(11) angstrom, beta = 142.95(5)-degrees, and Z = 4. Its structure is based on the packing of SmBr3.4iPr(OH) (iPr = isopropyl) molecules. The metal atom is coordinated by three Br ions and by the oxygen atoms of the four iPr(OH) ligands. The coordination polyhedron is a distorted pentagonal bipyramid of C2 symmetry, with Sm and one of the Br atoms lying on the twofold axis of crystallographic symmetry. Polymerization experiments are reported showing that the activity of the catalytic system based on the title complex is much lower than that shown by systems based on similar Nd complexes. A possible rationalization of this fact is given in terms of the oxidation capacity of the rare-earth ions.