Chemistry of Weakly Solvated Lanthanide-Metal Cations. Synthesis, Characterization, and Catalytic Chemistry of [Eu(Ch3Cn)3(Bf4)3)X

The title compound, [Eu(CH₃CN)₃(BF₄)₃)_x, 1, was synthesized by the NOBF₄ oxidation of metallic Eu in CH₃CN. The interaction of the BF₄^- ions with the Eu(III) center was established by molecular weight, conductivity, and ¹¹B and ¹⁹F NMR spectral measurements. 1 was found to exist as a dimer in CH₃CN. In addition, it behaved as a 1:2 electrolyte, indicating the coordination of two of the BF₄^- ions per Eu(III) ion. However, the conductivity increased when chelating amines were added due to the partial displacement of the coordinated BF₄^- ions. The ¹¹B and ¹⁹F NMR spectra of 1 in CH₃CN indicated the presence of two different types of BF₄^- anions, one of which was isotropically shifted due to interaction with the paramagnetic Eu(III) center. The coordinated BF₄^- anions could be displaced quantitatively by the addition of 2 equiv of N0₃^- ions per Eu(III) ion. A degenerate metathesis of the fluorine between the BF₃ and the coordinated BF₄^- ions was observed when BF₃ was added to a CH₃CN solution of 1. 1 formed a charge-transfer complex with tetra-p-anisylethylene in CH₃N0₂ but not in CH₃CN. In addition, 1 initiated the oligomerization and the polymerization of styrene, a-methylstyrene, and 1, 3-cyclohexadiene in CH₃N0₂. The molecular weights of the polymers obtained increased markedly on lowering the reaction temperature. At room temperature, indan derivatives were obtained from a-methyl- and a-phenylstyrene. The rate of polymerization of styrene was markedly attenuated when CH₃CN was used instead of CH₃N0₂. 1 also initiated the isomerization of quadricyclane and the ring-opening polymerization of 2(10)-pinene and cyclopropylbenzene in CH₃N0₂.