The chemistry of polyvalent iodine has seen significant development since the early 1990s, driven by the unique oxidizing properties and environmental safety of polyvalent organic iodine reagents. Iodine(III) and iodine(V) derivatives are widely used in organic synthesis for selective oxidative transformations. This review summarizes recent advances in the chemistry of polyvalent iodine compounds, focusing on their structure, bonding, synthetic applications, and reactivity. The review is organized by classes of organic polyvalent iodine compounds, emphasizing their synthetic utility. Polyvalent iodine compounds are classified into two main types: iodine(III) compounds (λ³-iodanes) and iodine(V) compounds (λ⁵-iodanes). Iodine(III) compounds have a distorted trigonal bipyramidal geometry with two heteroatom ligands in the apical positions and a carbon ligand in the equatorial positions. Iodine(V) compounds have a distorted octahedral structure with an aromatic group and an electron pair in the apical positions and four heteroatom ligands in the basal positions. These compounds are highly reactive and are used as oxidants and electrophilic agents in organic synthesis. Computational studies have provided insights into the bonding and reactivity of polyvalent iodine compounds. These studies have shown that the bonding in λ³-iodanes involves a three-center, four-electron (3c–4e) bond, which is highly polarized and weaker than a regular covalent bond. Theoretical investigations have also revealed the importance of secondary bonding in hypervalent molecules and the role of trans influences in stabilizing these molecules. Experimental structural studies have confirmed the polymeric nature of iodosylbenzene and its ability to form secondary bonds. The structure of iodosylbenzene has been studied using X-ray crystallography, revealing a zigzag polymeric structure with intermolecular I••O secondary bonds. Theoretical calculations have also supported these findings, showing the importance of hydration in the structure of iodosylbenzene. The review also covers the preparation, structure, and reactivity of various polyvalent iodine compounds, including iodosylarenes, fluorides, chlorides, and other derivatives. These compounds are used in a wide range of synthetic applications, including oxidation reactions, chlorination, and fluorination. The review highlights the importance of these compounds in organic synthesis and their potential for future applications.The chemistry of polyvalent iodine has seen significant development since the early 1990s, driven by the unique oxidizing properties and environmental safety of polyvalent organic iodine reagents. Iodine(III) and iodine(V) derivatives are widely used in organic synthesis for selective oxidative transformations. This review summarizes recent advances in the chemistry of polyvalent iodine compounds, focusing on their structure, bonding, synthetic applications, and reactivity. The review is organized by classes of organic polyvalent iodine compounds, emphasizing their synthetic utility. Polyvalent iodine compounds are classified into two main types: iodine(III) compounds (λ³-iodanes) and iodine(V) compounds (λ⁵-iodanes). Iodine(III) compounds have a distorted trigonal bipyramidal geometry with two heteroatom ligands in the apical positions and a carbon ligand in the equatorial positions. Iodine(V) compounds have a distorted octahedral structure with an aromatic group and an electron pair in the apical positions and four heteroatom ligands in the basal positions. These compounds are highly reactive and are used as oxidants and electrophilic agents in organic synthesis. Computational studies have provided insights into the bonding and reactivity of polyvalent iodine compounds. These studies have shown that the bonding in λ³-iodanes involves a three-center, four-electron (3c–4e) bond, which is highly polarized and weaker than a regular covalent bond. Theoretical investigations have also revealed the importance of secondary bonding in hypervalent molecules and the role of trans influences in stabilizing these molecules. Experimental structural studies have confirmed the polymeric nature of iodosylbenzene and its ability to form secondary bonds. The structure of iodosylbenzene has been studied using X-ray crystallography, revealing a zigzag polymeric structure with intermolecular I••O secondary bonds. Theoretical calculations have also supported these findings, showing the importance of hydration in the structure of iodosylbenzene. The review also covers the preparation, structure, and reactivity of various polyvalent iodine compounds, including iodosylarenes, fluorides, chlorides, and other derivatives. These compounds are used in a wide range of synthetic applications, including oxidation reactions, chlorination, and fluorination. The review highlights the importance of these compounds in organic synthesis and their potential for future applications.