Synthesis, reactions, and crystal structure of a stable 10-I-4 periodonium ion

The structure of the 10-I-4 periodonium ion of bis[α,α-bis(trifluoromethyl)benzenemethanolato(2-)-C 2 , O α ]iodine (1+) triflate, salt 1a, was confirmed by an X-ray crystallographic structure determination. The periodonium ion of 1a was the first example of a stable cationic 10-I-4 species lacking fluorine ligands. In contrast to other periodonium ions, that of 1a is not hydrolyzed by atmospheric moisture nor by water in neutral or acidic media. It does not react with weak nucleophiles such as pyridine or methanol.The lack of reactivity of the periodonium ion of 1a is better rationalized by comparision with other spirobicyclic 10-X-4 systems than with other known 12-I-5 or 10-I-4 species.Stricking parallels between the structures and properties of 10-X-4 species with identical bidentate ligands support the idea that properties of isovalent and isostructural hypervalent 10-X-4 species are predictable on the basis of ligand properties.Indeed the most stricking aspect of the reactivity of the periodonium ion of 1a is how little it resembles the reactivity of other the reactivity of other known iodine species in the same oxidation state.This is direct result of the specific geometry and electron distribution imposed on the central atom of a 10-X-4 species by the spirobicyclic ligand system, which was designed for specific stabilizing features for Ψ-TBP and TBP 10-X-L systems