An asymmetric trihydrido-bridged arene ruthenium complex

Reaction of [Ru(η6-indane)(H2O)3]2+ and [Ru(η6-C6Me6)(H2O)3]2+ with NaBH4 in water gives a mixture of three triple hydrido-bridged arene ruthenium cations [(η6-arene)Ru(μ-H)3Ru(η6-arene′)]+ (arene=indane and hexamethylbenzene; arene′=indane and hexamethylbenzene). After treatment with NaBF4, the three complexes are separated by column chromatography and the asymmetrical [(η6-indane)Ru(μ-H)3Ru(η6-C6Me6)][BF4] (cation 1a) can be isolated in moderate yield. 1a decomposes in solution to give the corresponding hydroxo-bridged complex [(η6-indane)Ru(μ-OH)3Ru(η6-C6Me6)]+ (2) with retention of the asymmetrical geometry as shown by single-crystal X-ray structure analysis. The indane ligand adopts an envelope conformation toward the ruthenium atom.