Crystal structures of rac- and meso-o-Phenylenebis(iodomethylarsine), the latter as its lattice complex with the methiodide of 1,3-Dimethyl-1,3-dihydro-2,1,3-benzoxadiarsole

Abstract

The crystal structures of the title compounds, o-C6H4(AsMeI)2 (1), and o- C6H4(AsMeI)2- [o-C6H4(AsMe)(As+Me2)O] I- (2), have been determined at 295 K by single-crystal X-ray diffraction and refined by least squares to residuals of 0.037 and 0.067 for 2095 and 2913 reflections respectively. Crystals of (1) are triclinic, Pī, a 9.865(5), b 9.837(7), c 7.765(4) Ǻ, α 98.89(5), β 96.71(4), γ 60.72(4)�, Z 2. <As- I> is 2.585 Ǻ and <As-C> 1.97 Ǻ. The angles about the arsenic differ only trivially, the mean being 98.4�. Crystals of (2) are monoclinic, P21/n, a 15.315(4), b 21.511(8), c 7.952(2) Ǻ, β 98.19(2)�, Z 4. In the cation As-O distances are unequal [1.75(1) (quaternary As), 1.86(2) Ǻ]; As-O-As is very small being 115.8(8)�. Charge-transfer interactions between iodine species are present in both derivatives; in (2), there is an interaction between the tertiary arsenics of the meso molecule and the iodide anion, As...I being 3.307(3), 3.551(3) Ǻ, with the geometry of the arsenics approaching that of a tetrahedral disposition. Within the cation, the geometry about the quaternary arsenic is typical of arsenic(v), the bond lengths being shorter than those about the ternary arsenic.