FERROMAGNETIC BEHAVIOR OF LINEAR-CHAIN ELECTRON-TRANSFER COMPLEXES - SYNTHESIS AND CHARACTERIZATION OF DECAETHYLFERROCENE, FE(C5ET5)2, AND ITS ELECTRON-TRANSFER SALTS - STRUCTURE AND MAGNETIC-PROPERTIES OF [FE(C5ET5)2].+[A].- [A = TCNE AND TCNQ]

1,2,3,4,5-Pentaethylcyclopentadiene as well as Fe(C5Et5)2 (D) and several electron-transfer salts have been prepared. The structure of the [TCNQ].- (A) salt has been determined [A = 9.416 (2) angstrom, b = 9.966 (1) angstrom, c = 11.710 angstrom, alpha = 93.83 (1)-degrees, beta = 109.29 (1)-degrees, gamma = 109.05 (1)-degrees, V = 961.4 angstrom 3, Z = 1, T = -70-degrees-C] to have a ...D.+A.-D.+A.-... structural motif. The Fe-57 Mossbauer spectra of [TCNE].- and [TCNQ].- salts of [Fe(C5Et5)2].+ are typical of ferrocenium ions and magnetic hyperfine splitting characteristic of either slow paramagnetic relaxation or extended magnetic order is not observed above 1.5 K. The 5-K EPR spectrum of [Fe(C5Et5)2].+ has a strong absorption at g parallel-to = 4.59. The Faraday magnetic susceptibility (2-320 K) can be fit to the Curie-Weiss expression, mu-eff = 3.37, 3.15, and 3.62-mu-B and theta = 6.9, 7.5, and 6.1 K, for the [PF6]-, [TCNE].-, and [TCNQ]- salts of [Fe(C5Et5)2].+, consistent with ferromagnetic coupling, respectively.