Synthesis of the cyclohexadienyl ruthenium arene complexes [(η5-C6H3Me4)Ru(η6-arene)]+ from the dimethyloctadienyl ruthenium chloride[(μ-η3:η3-C10H16)RuCl2]2

• A new approach to substituted cyclohexadienyl ruthenium arene complexes was developed.
• Tetramethylcyclohexadienyl ligand can undergo C–Me bond cleavage to give mesitylene.
• Dimethyloctadiendiyl ligand can be transformed into substituted pentadienyl ligand.

Reaction of the readily accessible dimethyloctadienyl ruthenium chloride [(μ-η3:η3-C10H16)RuCl2]2 (1) with 1,3,5,5-tetramethylcyclohexadiene and arenes in the presence of TlPF6 gives cyclohexadienyl ruthenium arene complexes [(η5-C6H3Me4)Ru(η6-arene)]+ in ca. 50% yield (arene = benzene, naphthalene, pyrene, thiophene, ethyl ester of N-acetyl-phenylalanine). In the absence of appropriate arene the major product is the mesitylene complex [(η5-C6H3Me4)Ru(η6-C6H3Me3)]+ formed via splitting of the C–Me bond in the 1,3,5,5-tetramethylcyclohexadienyl ligand. The reaction of 1 with p-xylene and TlPF6 in the absence of diene gives a methyl-isobutyl substituted pentadienyl complex [(η5-C5H5(iBu)Me)Ru(η6-C6H4Me2)]+ (6) via isomerization of the dimethyloctadienyl ligand. The structures of [(η5-C6H3Me4)Ru(η6-naphthalene)]PF6 and [6]BPh4 were confirmed by X-ray diffraction.

A variety of cyclohexadienyl ruthenium arene complexes were synthesized from the readily available precursors: chloride [(C10H16)RuCl2]2 and tetramethylcyclohexadiene.Figure optionsDownload as PowerPoint slide