Typical Kumada cross-coupling reaction has always been associated with the formation of one C–C bond per each initial reactive C–I unit. This has also been the case for B–C cross-coupling starting from a single B–I. For the first time in this paper, diarylation in two distinct sites of a metallacarborane to generate two B–C bonds has been demonstrated, starting from a single B–I. The achievement has been possible by reacting Cs[3,3′-Co(8-I-1,2-C2B9H10) (1′,2′-C2B9H11)] with the 4-bromobiphenyl Grignard reagent in the presence of [PdCl2(PPh3)2] and CuI as co-catalyst. All experimental data including its X-ray crystal diffraction confirm the results.