Emma Seppälä

Tuning seleniumiodine contacts: from secondary soft–soft interactions to covalent bonds

Selenium to iodine contacts ranging from the sum of the Se and I van der Waals distances to strong covalent bonds are reviewed with the help of recent structural determinations of compounds exhibiting SeI distances from 384 to 244 pm, with emphasis on ‘less clear-cut’ cases, in terms of different extents of ‘hypervalent’ 3c–4e (10-Se-3) and (10-I-2) interactions. Within a continuum of SeI interactions from undisturbed single bonds via n->σ*(SeI) interactions and typical 3c–4e XSeI or SeIX systems to van der Waals contacts, any desired SeI distances can be tuned by an appropriate choice of the particular substituents and ligands attached to the SeI moiety.

Coordination and oxidation of phosphine selenides with iodine: from cation pairs [(R3PSe)2I+]2 to (iodoseleno)phosphonium ions [R3PSeI]+ existing as guests in polyiodide matrices

An X-ray crystallographic study of adducts of trialkylphosphine selenides with >1 equivalent of diiodine reveals that solid But3PSeI3 consists of cation pairs [(But3PSe)2I+]2 intercalated between I5– layers and that solid R2R′PSeI7 (R = But or Pri, R′ = Pri) contains [R2R′P–Se–I]+ cations with weak secondary I‥I interactions to polyiodide networks.