Electron transfer in groups of iron, cobalt, and copper triazene 1-oxides: Hammett correlation, ligand redistribution, and crystal field effects

Mukherjee, R. N. ; Rajan, O. A. ; Chakravorty, A. (1982) Electron transfer in groups of iron, cobalt, and copper triazene 1-oxides: Hammett correlation, ligand redistribution, and crystal field effects Inorganic Chemistry, 21 (2). pp. 785-790. ISSN 0020-1669

Full text not available from this repository.

Official URL: http://pubs.acs.org/doi/abs/10.1021/ic00132a062

Related URL: http://dx.doi.org/10.1021/ic00132a062

Abstract

The electron-transfer behavior of groups of pseudooctahedral ML3 and grossly planar Ca, complexes is reported (M Fe. Co; L triazene 1-oxide). A quasi-reversible proccess of type MLp+ e-⇌ML3(p=2,3) is identified with electrochemical techniques. The E°298 values (vs. SCE) fall in the following ranges: Fe, -O.76 to -0.14; Co, -0.56 to -0.08; Cu, -1.07 to -0.37. The values become more negative in the order CoL3, FeL3, and CuL2. For a given metal ion, E°298 shifts appreciably with ligand substituent. and a linear Hammett relationship is obeyed. The reaction constant is shown to decrease considerably when an extra bond intervenes between the metal and the substituent. Copper(II) complexes of bidentate ligands carrying an ortho substituent as well as the of a tetradentate ligand that enforce cis planar stereochemistry display abnormally negative shifts of E°298. When two iron(III) complexes are mixed, ligand scrambling occurs and the presence of mixed species is neatly established by cyclic voltammetry. The mixed complexes fit smoothly into the Hammett straight lines. The thermodynamic quantities controlling the trends of E°298 are considered. An attempt is made to assess the relative importance of spherical and nonspherical parts of the crystal fields. Among complexes of the same metal ion, it is possible to express the shift of E°298 in terms of the crystal field splitting parameter with a large proportionality constant. The copper(II) complexes show a ligand field band whose energy linearly correlates with E°298. The shift of E°298 between iron and cobalt couples is controlled by metal ionization potential and nearly equally important spherical and nonspherical crystal field contributions.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:95282
Deposited On:30 Oct 2012 05:51
Last Modified:30 Oct 2012 05:51

Repository Staff Only: item control page