A series of heterocyclic hypervalent (HV) iodine(III) compounds containing fused tetrazole and benziodazole rings, i.e., derivatives of benziodazolotetrazole (BIAT) with various ligands (L) attached to the iodine atom (BIAT-L) were prepared and studied. They were characterized by ¹H and ¹³C NMR spectroscopy, ESI-HRMS, and X-ray crystallography. The thermal stabilities of all BIAT derivatives (L= Cl, OH, OAc, OMe) were studied and the degradation patterns as well as the enthalpies of degradation were measured by thermal gravimetric analysis coupled with differential scanning calorimetry. The reaction of various alkenes with BIAT-Cl in the presence of Cu(OTf)₂ at room temperature yielded chloro-tetrazolylated products. The oxidation of thioanisole with BIAT-Cl under various reaction conditions is also reported.