Self-assembly in organoselenium compounds

Several inorganic compounds of selenium are known to contain secondary bonds, but only organoselenium derivatives will be covered here. Among these, the organoselenium halides are of interest, because selenium iodides were - for many years -considered not to exist the compounds have recently become available [477]. 

The first structurally characterized arylselenium compound, 2,4,6-Bu 3C6H2SeI, was found to be monomeric in the crystal, without significant intermolecular Se- I, I- -I, or Se - -Se contacts [478]. Attempts to grow crystals of the related 2,4,6-Pr 3C6H2SeI produced an adduct of the corresponding diselenide with molecular iodine, 201. The adduct is the product of self-assembly by secondary bonding between iodine and two selenium atoms from adjacent molecules. 

The compound has been described (not quite appropriately) as an intercalation compound of solid diselenide with half equivalents of iodine. 

More interesting is the structure of the diphenyldiselane-diiodine adduct, which is an eight-membered quasi-cyclic compound, 202, formed by secondary bonding (Se- -I 2.992 and 3.588 A) [479]. The sum of the van der Waals radii for selenium and iodine is 3.88 A. 

Mesitylselenium iodide, 2,4,6-Me3C6H2SeI, has a supramolecular self-organized architecture, 203, based on secondary bonds between iodine and iodine, and between iodine and selenium pairs. Similar self-organization by secondary bonding 

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