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Issue 8, 2013
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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

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Abstract

The reactions of the diaryl-diselenides (p-FC6H4)2Se2 and (p-ClC6H4)2Se2 with diiodine have been investigated. Species of stoichiometry “RSeI” are formed when the ratio employed is 1 : 1. The solid-state structure of “(p-FC6H4)SeI” has been determined, and shown to be a charge-transfer (CT) adduct, (p-FC6H4)2Se2I2, where the Se–Se bond is retained and the diiodine molecule interacts with only one of the selenium atoms. The Se–I bond in (p-FC6H4)2Se2I2 is 2.9835(12) Å, which is typical for a (10-I-2) Se–I–I CT system. When diiodine is reacted in a 3 : 1 ratio with (p-XC6H4)2Se2 (X = F, Cl) species of stoichiometry “RSeI3” are formed. The structure of “(p-ClC6H4)SeI3” reveals that this is not a selenium(IV) compound, but is better represented as a selenium(II) CT adduct, (p-ClC6H4)SeI·I2. The Se–I bond to the diiodine molecule is typical in magnitude for a CT adduct, Se–I: 2.8672(5) Å, whereas the other Se–I bond is much shorter, Se–I: 2.5590(6) Å, and is a genuine example of a rarely observed covalent Se–I bond, which appears to be stabilised by a weak Se⋯I interaction from a neighbouring iodine atom. The reaction of (p-ClC6H4)SeI with Ph3P results in the formation of a CT adduct, Ph3PSe(p-ClC6H4)I, which has a T-shaped geometry at selenium (10-Se-3). By contrast, the reaction of (p-FC6H4)SeI with Ph3P does not form an adduct, but results in the formation of Ph3PI2 and (p-FC6H4)2Se2.

Graphical abstract: 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

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Publication details

The article was received on 22 Aug 2012, accepted on 28 Nov 2012 and first published on 28 Nov 2012


Article type: Paper
DOI: 10.1039/C2DT31921G
Citation: Dalton Trans., 2013,42, 2735-2744
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    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

    N. A. Barnes, S. M. Godfrey, J. Hughes, R. Z. Khan, I. Mushtaq, R. T. A. Ollerenshaw, R. G. Pritchard and S. Sarwar, Dalton Trans., 2013, 42, 2735
    DOI: 10.1039/C2DT31921G

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