Accession Number : ADA188779

Title :   The Orbital-Overlap Factor in Electron Transfer. Sensitivity of Homogeneous Self-Exchange Kinetics for Some Metallocenes to Electronic Structure.

Descriptive Note : Technical rept. 1 Oct 86-30 Sep 87,

Corporate Author : PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY

Personal Author(s) : Nielson, Roger M ; Golovin, M N ; McManis, George E ; Weaver, Michael J

PDF Url : ADA188779

Report Date : 25 Sep 1987

Pagination or Media Count : 22

Abstract : Rate constants, k(h)(ex), for the electron self exchange of cobaltocenium-cobaltocene, Cp2Co(+/o), and for the decamethyl derivative (Cp-Me5)2Co(+/0) obtained by using the NMR line broadening technique in acetonitrile and dimethylsulfoxide are compared with corresponding data for the ferrocene couples Cp2Fe(+/0) and (Cp-Me5)(2)Fe(+/0) and bis(benzene)chromium (I)/(O). The rate constants in a given solvent display and marked sensitivity to the reactant structure, the kh(ex) values being about tenfold larger for Cp2Do(+/0) relative to Cp2Fe(+/0); decamethyl substitution yields tenfold increases in kh(ex) for both these couples. A relationship is established between these ca. 100 fold rate variations and the nature of the donor and acceptor orbitals. In particular, the markedly slower self-exchange kinetics observed for Cp2Fe(+/0) relative to Cp2Co(+/0) are consistent with the much greater ligand-delocalized character of the Ze(lg) orbital involved in the latter electron transfer are compared with the 4e(2) or 8a(lg) orbital for the former reaction. Keywords: Line broadening, Electron transfer, Metallocenes, Orbital overlap factor.

Descriptors :   *ELECTRON TRANSFER, *ORGANOMETALLIC COMPOUNDS, *REACTION KINETICS, *MOLECULAR ORBITALS, ACETONITRILE, CONSTANTS, OVERLAP, REACTANTS(CHEMISTRY), SOLVENTS, ELECTROCHEMISTRY, IRON, COBALT, CATIONS, LIGANDS, COUPLING(INTERACTION), NUCLEAR MAGNETIC RESONANCE

Subject Categories : Physical Chemistry
      Organic Chemistry
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE