The potassium salts of the new S₂N-heteroscorpionate ligand hydrobis(methimazolyl)(3,5-dimethylpyrazolyl)borate [HB(mt)₂(pz^3,5-Me)]⁻ and its known analogue hydrobis(methimazolyl)(pyrazolyl)borate [HB(mt)₂(pz)]⁻ (prepared from KTp′ or KTp and methimazole, Hmt), and the adduct KTp·Hmt have polymeric structures in the solid state (the first a ladder and the other two chains). The iridaboratranes [IrHLL′{B(mt)₂X}] (X = pz^3,5-Me or pz), prepared from the heteroscorpionate anion and [{Ir(cod)(μ-Cl)}₂] (LL′ = cod), subsequent carbonylation [LL′ = (CO)₂] and then reaction with phosphine [LL′ = (CO)(PR₃), R = Ph or Cy], have a pendant pyrazolyl ring and a bicyclo-[3.3.0] cage formed by an S₂-bound B(mt)₂ fragment. The binuclear species [(cod)HIr{μ-B(mt)₃}IrCl(cod)], the only isolated product of the reaction of KTm with [{Ir(cod)(μ-Cl)}₂], also has an S₂-bound iridaboratrane unit but with the third mt ring linked to square planar iridium(I).