An addition reaction of dinuclear [(η6‐C6Me6)Ru(η3, 1‐exo‐syn‐CH2CHCHCHO)]2(BF4)2 (1) with different Lewis bases in acetone results in the formation of mononuclear [(η6‐C6Me6)Ru(η3‐exo‐syn‐CH2CHCHCHO)(L)](BF4) (L = PMe3, 2; PPh3, 3; PHPh2, 4; Ph2PEtPy, 6; CO, 7) and dinuclear [{(η6‐C6Me6)Ru(η3‐exo‐syn‐CH2CHCHCHO)}2(μ2‐dppe)](BF4)2 (5). The addition of Ph2PCH2CH2PPh2 to the dinuclear product 1 affords 5 which show a bridging phosphine between two ruthenium centers. A comparative study of the new cationic arene derivatives and the corresponding isoelectronic Cp*Ru(heteropentadienyl) is established. All compounds were characterized by IR spectroscopy, high resolution mass spectrometry, NMR spectroscopy and the crystal structures of 2 and 3 are also described.