Tuning selenium-iodine 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- > sigma*(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. (C) 2001 Elsevier Science B.V. All rights reserved.