MULTIPLE BONDS BETWEEN MAIN-GROUP ELEMENTS AND TRANSITION-METALS .130. (CYCLOPENTADIENYL)TRIOXORHENIUM(VII) - SYNTHESIS, DERIVATIVES, AND PROPERTIES

(Eta5-Cyclopentadienyl)trioxorhenium(VII) and ring-substituted derivat ives are conveniently synthesized from (trifluoroacetyl)perrhenate and substituted (cyclopentadienyl)tin compounds. As shown by cyclovoltamm etry, peralkylated (cyclopentadienyl)tin derivatives undergo redox rea ctions with Re(VII) precursor compounds such as (trifluoroacetyl)triox orhenium(VII). The reduction potentials of peralkylated CpRe(VII) syst ems differ significantly from those of the nonalkylated forms. Thermal stabilities of CpReO3 derivatives increase with the number of methyl groups in the Cp ring, reflecting increasing Re-C bond strengths resul ting from the electron density of the pi-bonded ligands. Increasing pi -donor capability of the Cp ligands with increasing substitution by al kyl groups is documented in the IR and O-17 NMR spectra. As shown by a single-crystal X-ray diffraction analysis of (C5H5)ReO3, the Cp ligan d is eta5-bonded to the metal. Crystal data: monoclinic P2(1)/m, a = 5 .984(1) angstrom, b = 9.179(1) angstrom, c = 6.099(1) angstrom, beta = 116.30(1)-degrees, R = 0.021 for 559 reflections.