Synthesis and Structures of Ru(II)-p-Cymene Sandwich Complexes with Electron-Withdrawing Cyclopentadienyl Ligands

A modular synthetic route has been developed to prepare a new series of cationic ruthenium(II) complexes with electron-withdrawing 1,2-diacylcyclopentadienyl ligands. The 2-acyl-6-hydroxyfulvenes were synthesized from cyclopentadienide and acyl chlorides and converted to Tl(I) cyclopentadienyl salts using Tl2SO4/KOH. Transmetalation with [Ru(η6-p-cymene)(μ-Cl)Cl]2 followed by PF6− metathesis gives the complexes [Ru{η5-1,2-C5H3(CO–R)2}(η6-p-cymene)][PF6] (R = t-Bu, p-Tol, p-ClC6H4, p-IC6H4) in moderate to high yields. The new compounds were characterized by NMR and IR spectroscopy; mass spectrometry and elemental analysis were performed where applicable. X-ray analysis of one of the complexes confirms that electron-deficient Cp ligands retain η5-coordination and structural planarity within Ru(II)–arene sandwich architectures, highlighting their potential utility in electronically tunable organometallic frameworks.