Cationic half-sandwich ruthenium(II) complexes with cyclopentadienyl- phosphine ligands

Article abstract of DOI:10.1016/S0020-1693(02)01502-5

The reaction of [Ru(η³:η³-C ₁₀H₁₆)Cl₂]₂ (1) with the Cp-linked phosphine ligands L_n (C₅H₅-CH ₂CHRPR′₂; R=H, R′=Ph, n=1; R=Ph, R′=Ph, n=2), in a 5:1 mixture of acetonitrile-ethanol and in the presence of Li ₂CO₃ and KPF₆ affords the cationic half-sandwich ruthenium(II) complexes [{η⁵-C₅H ₄-CH₂CHRPR′₂-κP}Ru(CH ₃CN)₂]·[PF₆] (4) and (5). Both complexes have been characterized in the solid state by an X-ray structure analysis. In contrast, the reaction between 1 and L₃ (R=Ph, R′=o-xylyl) affords the cationic sandwich compound [{η ⁵:η⁶-C₅H₄- CH₂CHPhPR′₂}Ru]·[PF₆] (7), in which one arene substituent of the phosphine is η⁶-coordinated to the metal and the phosphorus remains pendant. Treatment of 5 with tertiary phosphines (PR″₃, R″=i-Pr, Ph, Cy) affords a mixture of the diastereomers [L₂Ru(CH₃CN)PR″₃] ⁺. The diastereoselectivity observed depends on the steric bulkiness of the phosphines and on the reaction conditions.