Reaction of [1,2-(Cp*RuH)2B3H 7](1;Cp* = η-C5Me5) with [Mo(CO) 3(CH3CN)3] yielded arachno-[(Cp*RuCO) 2B2H6](2), which exhibits a butterfly structure, reminiscent of 7 sep B4H10. Compound 2 was found to be a very good precursor for the generation of bridged borylene species. Mild pyrolysis of 2 with [Fe2(CO)9] yielded a triply bridged heterotrinuclear borylene complex [(μ3-BH) (Cp*RuCO)2(μ-CO){Fe(CO)3}] (3) and bis-borylene complexes [{(μ3-BH)-(Cp*Ru)(μ-CO)}2Fe 2(CO)5](4) and [{(μ3-BH)(Cp*Ru)Fe(CO) 3}2(μ-CO)] (5). In a similar fashion, pyrolysis of 2 with [Mn2(CO)10] permits the isolation of μ3-borylene complex [(μ3-BH)-(Cp*RuCO) 2(μ-H)(μ-CO){Mn(CO)3}] (6) . Both compounds 3 and 6 have a trigonal-pyramidal geometry with the μ3-BH ligand occupying the apical vertex, whereas 4 and 5 can be viewed as bicapped tetrahedra, with two μ3-borylene ligands occupying the capping position. The synthesis of tantalum borylene complex [(μ3-BH)(Cp*TaCO) 2(μ-CO){Fe(CO)3}] (7) was achieved by the reaction of [(Cp*Ta)2B4H8(μ-BH4)] at ambient temperature with [Fe2(CO)9]. Compounds 2-7 have been isolated in modest yield as yellow to red crystalline solids. All the new compounds have been characterized in solution by mass spectrometry; IR spectroscopy; and 1H, 11B, and 13C NMR spectroscopy and the structural types were unequivocally established by crystallographic analysis of 2-6. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.