Synthesis and molecular structure of the trinuclear ruthenium cluster cations [H3Ru3{C6H5(CH2)2OC(O)C6H5}(C6Me6)2(O)]+ and [H3Ru3{C6H5(CH2)2OC(O)(CH2)3C6H5}(C6Me6)2(O)]+

Benzoic acid 2-cyclohexa-1,4-dienyl ethyl ester (1), and 4-phenylbutyric acid 2-cyclohexa-1,4-dienyl ethyl ester (2) are prepared by reacting, respectively, benzoic acid and 4-phenylbutyric acid with 2-cyclohexa-1,4-dienyl ethanol. These dienyl ester derivatives react with RuCl3 · n H2O in refluxing ethanol to afford in good yield [Ru{C6H5(CH2)2OC(O)C6H5}Cl2] 2 (3), and [Ru{C6H5(CH2)2OC(O)(CH2)3C6H5}Cl2]2 (4). The trinuclear arene–ruthenium cluster cations [H3Ru3{C6H5(CH2)2OC(O)C6H5}(C6Me6)2(O)]+ (5), and [H3Ru3{C6H5(CH2)2OC(O)(CH2)3C6H5}(C6Me6)2(O)]+ (6) are synthesised from the dinuclear precursor [H3Ru2(C6Me6)2]+, and the mononuclear complexes [Ru{C6H5(CH2)2OC(O)C6H5}(H2O)3]2+ and [Ru{C6H5(CH2)2OC(O)(CH2)3C6H5}(H2O)3]2+, accessible, respectively, from 3 and 4 in aqueous solution. The water-soluble trinuclear cluster cations 5, and 6 possess a phenyl substituent attach to their side-arm which can act as a substrate for hydrogenation. The single-crystal X-ray structure analyses of [5][PF6], and [6][PF6] have been determined.