Electron-transfer barriers and metal-ligand bonding as a function of metal oxidation state. 3. Crystal and molecular structures of tris(2,2'-bipyridine)nickel(III) triperchlorate-2-acetonitrile-0.5-dichloromethane

Abstract

The structure of tris(2,2'-bipyridine)nickel(III) triperchlorate-2-acetonitrile-0.5-dichloromethane, (Ni(C/sub 10/H/sub 8/N/sub 2/)/sub 3/)(Cl-O/sub 4/)/sub 3/.2CH/sub 3/CN.0.5CH/sub 2/Cl/sub 2/, has been determined. The nickel(III) complex crystallizes inthe triclinic crystal system, space group P1, with a = 11.193 (1) A, b = 17.634 (3) A, c = 10.494 (2) A, ..cap alpha.. = 95.41 (1)/sup 0/, ..beta.. = 107.02 (2)/sup 0/, ..gamma.. = 95.28 (1)/sup 0/, and Z = 2. The structure was refined to a final R value of 0.096. The coordination sphere consists of the six nitrogen atoms of the three bipyridine ligands in a tetragonally distorted octahedral arrangement about the nickel. The six nickel-nitrogen bonds form three sets with two pairs of longer equatorial bonds, 2.022 (6) and 2.000 (5) A, and a pair of shorter axial bonds, 1.924 (6) A. The metal-ligand bond distances in Ni(bpy)/sub 3//sup 3 +/ and related complexes are rationalized in terms of their electronic configurations. The electron-transfer barrier for the Ni(bpy)/sub 3//sup 3 +/-Ni(bpy)/sub 3//sup 2 +/ exchange is related to the bond length differences in the two oxidation states and is compared with the barrier for electron transfer between other polypyridine complexes. 52 references, 2 figures, 4 tables.