The reaction of N-methylbenzothiazole-2-selone with the interhalogens iodine monobromide and iodine monochloride

Two 1:1 interhalogen adducts of N-methylbenzothiazole-2-selone (mbts) have been prepared and crystallographically characterised: mbts . IBr (1) and mb ts . ICl (2). Both exhibit the charge transfer 'spoke' structure consisting of a linear Se-I-X arrangement (X=Br or Cl) where d(C-Se) increases from t hat seen for mbts by 0.058(5) and 0.062(8) Angstrom (1 and 2 respectively); d(C-N) decreases by 0.019(4) and 0.019(9) Angstrom. This indicates electro n density moves towards the Se-I-X moiety upon co-ordination, causing a par tial positive charge to reside on the nitrogen atom. The I-X bond lengthens with respect to the unco-ordinated species for both molecules. The additio n of two equivalents of ICl to mbts gave a dark purple material of stoichio metry C8H7Cl2.9I1.1NSSe 3; the fractional stoichiometry for iodine and chlo rine may be indicative of 'halogen scrambling'. An additional product from this reaction was examined crystallographically and found to consist of the ion pair [C8H7NSCl](+)[ICl2](-) 4, i.e. the C-Se double bond has been comp letely cleaved and replaced by a C-Cl single bond. The positive charge is a gain supported mostly by the nitrogen atom; d(C-N) decreases to 1.294(10) A ngstrom indicating a double bond.