Formation of three-vertex metallaboranes from monoborane precursors: X-ray crystal structures of the molybdenum and ruthenium complexes [Mo(η-C 5 H 5 ) 2 H(η 2 -B 2 H 5 )] and [Ru(η-C 5 Me 5 )(PMe 3 )(η 2 -B 2 H 7 )]

The novel three-vertex metallaborane [Ru(η–C5Me5)(PMe3)(η2-B2H7)](1) has been synthesised by reaction of [Ru(η-C5Me5)(PMe3)Cl2] with NaBH4; homologation is also observed in the reaction of [Mo(η-C5H5)2H2] with BH3·THF, which forms [Mo(η-C5H5)2H(η2-B2H5)](2); X-ray crystal structures of compounds (1) and (2) are reported.