An Unusual Geometry of Five-Coordinate Copper(II): The Structure of Cu(terpy)I2 and Spectroscopic Investigations of Complexes Cu(terpy)X2 (X: I, NCS)

The structure of the compound Cu(terpy)I2 (terpy 2,2′: 6′, 2″ terpyridine) was determined at room temperature. It is monoclinic, space group I2/c with a = 13.689(3), b = 9.510(2), c = 11.605(3) Å, β = 97.59(4)° and Ζ = 4. The copper(II) ions are five-coordinated by the three nitrogen atoms from the terpy ligand and the two iodine atoms. The CuN3I2 polyhedron exhibits the same unusual “reverse” geometry as is observed for Cu(terpy)(NCS)2. Single crystal EPR measurements of the iodide and the isothio-cyanate complexes confirmed the structural results, excluding the possibility of a dynamically averaged geometry.

Miscellanea. Inorganic Thermochromism. By K. Sone and Y. Fukuda. Springer, Berlin 1987. xi, 134 pp., bound, DM 168.00.—ISBN 3-540-17662-4

An EPR investigation of the phase transitions and cooperative ordering phenomena of pentaamminecopper(II) polyhedra in Cu(NH3)5X2 [X=BF4, CIO4; Br]

The results of powder and single-crystal EPR studies on Cu(NH3)5X2 compounds [X=BF4, CIO4; Br] give evidence that phase transitions from a cubic α-phase (g i ≃2.12) with an anti-K2PtCl6 type structure to low-temperature β-phases with reduced symmetry occur, which are induced by ordering processes of the vacancies □ of elongated [Cu(NH3)5□]2+ pseudo-octahedra. The type of order is crucially controlled, by the nature of the anion. In the case of the BF 4 − and ClO 4 − salts the large anions are structure-determining leading to a slightly disturbed antiferrodistortive order of the elongated CuIIN5 square pyramids atT c≃155 K and <130 K, respectively. The resulting pseudo-tetragonal β-structure…

Book Review: Inorganic Thermochromism. By K. Sone and Y. Fukuda