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 mbts . 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 that 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 electron density moves towards the Se-I-X moiety upon co-ordination, causing a partial positive charge to reside on the nitrogen atom. The I-X bond lengthens with respect to the unco-ordinated species for both molecules. The addition of two equivalents of ICl to mbts gave a dark purple material of stoichiometry C8H7Cl2.9I1.1NSSe 3; the fractional stoichiometry for iodine and chlorine 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 completely cleaved and replaced by a C-Cl single bond. The positive charge is again supported mostly by the nitrogen atom; d(C-N) decreases to 1.294(10) Angstrom indicating a double bond.