Department of Chemistry, Indian Institute of Technology Madras, Chennai-600 036, India E-mail: sghosh@iitm.ac.in Univ Rennes, CNRS, Institut des Sciences Chimiques de Rennes, UMR 6226, F-35000 Rennes, France Manuscript received online 15 September 2019, accepted 19 September 2019 In continuation of our recent studies on the reactivity of [(Cp*Nb)2 B4 H10O], I with metal carbonyls, we have carried out its reactivity with [Fe2 (CO)9 ] that led to the formation of [(Cp*Nb)2 B2 H4O{H2 Fe2 (CO)6 BH}], 1. Compound 1 is a heterometallic boride cluster in which [Nb2 Fe2 ] core describes a butterfly framework with one boron atom lying in a semi-interstitial position. Further, in an attempt to isolate the heterometallic metallaboranes of group 4, we have performed the thermolysis reaction of [Cp2 Hf(BH4 )2 ] with [Cp*IrB3 H9 ] that led to the formation of arachno-[(Cp2 Hf)(Cp*Ir)B3 H9 ], 2, analogous to [(Cp2 Zr)(Cp*Ir)B3 H9 ]. Compounds 1 and 2 have been characterized by mass spectrometry, 1H, 11B and 13C NMR spectroscopy and the structural types were unequivocally established by crystallographic analysis.