Thermolysis of an in situ generated intermediate [(Cp∗Ta)2(BH3)2Cl2], 1 generated from the reaction of [Cp∗TaCl4], (Cp∗ = η5-C5Me5) and [LiBH4•thf], in presence of [Ru3(CO)12] yielded pileo-[Cp∗TaCl(μ-Cl)-B2H4Ru3(CO)8], 2 having two electrons fewer than seven pairs required for the observed square pyramidal geometry. Cluster 2 is the first example of an unsaturated cluster comprising early and late transition metals in a square pyramid core. This reaction also yielded [(Cp∗Ta)2(B2H6)(B2H4Cl2)], 3 as a by-product. In addition, the reaction of [Cp∗MoCl4] (Cp∗ = η5-C5Me5) with [LiBH4·thf] in presence of excess [MeI] at mild condition led to the isolation of periodinated dimolybdatetraborane [(Cp∗Mo)2B4H3I5], 4 that hints a possible existence of [(Cp∗Mo)2B4H8]. After the isolation of periodinated 4, we extended this chemistry towards the late transition metallaborane [(Cp∗Rh)3B4H4], 5 using [PtBr2] as brominating source. Although all the attempts to isolate perbrominated rhodaborane failed, we have isolated partially brominated rhodaborane clusters [(Cp∗Rh)3(BH)-(BBr)3], 6 and [(Cp∗Rh)3(BH)3(BBr)], 7. All the compounds were characterized by IR and 1H, 11B and 13C NMR spectroscopy in solution, and the solidstate structures of 2, 4 and 6 were established by crystallographic analysis. © 2014 IUPAC & De Gruyter.