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 <b>1a</b>) can be isolated in moderate yield. <b>1a</b> decomposes in solution to give the corresponding hydroxo-bridged complex [(η⁶-indane)Ru(μ-OH)₃Ru(η⁶-C₆Me₆)]⁺ (<b>2</b>) 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.