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

The reaction of [Ru(η3:η3-C10H16)Cl2]2 (1) with the Cp-linked phosphine ligands Ln (C5H5CH2CHRPR′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 Li2CO3 and KPF6 affords the cationic half-sandwich ruthenium(II) complexes [{η5-C5H4CH2CHRPR′2-κP}Ru(CH3CN)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 [{η5: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.