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.