The reactions of para-halo diaryl diselenides with halogens. A structural investigation of the CT compound (p-FC6H4)2Se2I2, and the first reported “RSeI3” compound, (p-ClC6H4)SeI·I2, which contains a covalent Se-I bond.

The reactions of the diaryl-diselenides (p-FC(6)H(4))(2)Se(2) and (p-ClC(6)H(4))(2)Se(2) with diiodine have been investigated. Species of stoichiometry "RSeI" are formed when the ratio employed is 1:1. The solid-state structure of "(p-FC(6)H(4))SeI" has been determined, and shown to be a charge-transfer (CT) adduct, (p-FC(6)H(4))(2)Se(2)I(2), where the Se-Se bond is retained and the diiodine molecule interacts with only one of the selenium atoms.

Structural isomerism in (p-XC6H4)SeCl3 and (p-XC6H4)SeBr3 (X = F, Cl) compounds. Co-crystallisation of cis- and trans-dimeric forms of (p-ClC6H4)SeCl2(μ-Cl)2(p-ClC6H4)SeCl2. A new structural modification for the "PhSeBr" reagent, Ph2Se2Br2, containing an elongated Se-Se bond.

A series of di(para-halophenyl)diselenides, (p-XC(6)H(4))(2)Se(2) (X = F, Cl) have been reacted with three equivalents of SO(2)Cl(2) or Br(2), leading to the formation of selenium(iv) RSeX(3) compounds. The structures of (p-FC(6)H(4))SeX(3) (X = Cl, Br) have been determined, and both exhibit a dimeric RSeX(2)(μ-X)(2)RSeX(2) structure consisting of two "saw-horse" (p-FC(6)H(4))SeX(3) units linked by two halide bridges, with an overall square pyramidal geometry at selenium. In both structures all the selenium and halogen atoms are planar, with both aryl rings located on the same side of the Se(2)X(6) plane (cis-isomer).