Structure Polyhalogen ions



structures of isopolyhalogen cations




solid state structures of polyhalogen ions [brf2], [clf2], [icl2] in [sbf6] salts.




solid state structure of [i3cl2] in [i3cl2][ascl6].



structure of [i2f12] dimer present in [me4n][if6].


most of structures of ions have been determined ir spectroscopy, raman spectroscopy , x-ray crystallography. polyhalogen ions have heaviest , least electronegative halogen present in ion central atom, making ion asymmetric in cases. example, [cl2f] has structure of [cl–cl–f] not [cl–f–cl].


in general, structures of heteropolyhalogen ions , lower isopolyhalogen ions in agreement vsepr model. however, there exceptional cases. example, when central atom heavy , has 7 lone pairs, such [brf6] , [if6], have regular octahedral arrangement of fluoride ligands instead of distorted 1 due presence of stereochemically inert lone pair. more deviations ideal vsepr model found in solid state structures due strong cation-anion interactions, complicates interpretation of vibrational spectroscopic data. in known structures of polyhalogen anion salts, anions make close contact, via halogen bridges, counter-cations. example, in solid state, [if6] not regularly octahedral, solid state structure of [me4n][if6] reveals loosely bound [i2f11] dimers. significant cation-anion interactions found in [brf2][sbf6], [clf2][sbf6], [brf4][sb6f11].










‡ [if5] 1 of 2 xyn-type species known have rare pentagonal planar geometry, other being [xef5]. §[clf6] distorted octahedral stereochemical inert pair effect not significant in chlorine atom.



the [i3cl2] , [i3br2] ions have trans-z-type structure, analogous of [i5].



solid state structure of [brf4] in [brf4][sb2f11].



higher polyiodides

the polyiodide ions have more complicated structures. discrete polyiodides have linear sequence of iodine atoms , iodide ions, , described in terms of association between i2, , i−

3 units, reflects origin of polyiodide. in solid states, polyiodides can interact each other form chains, rings, or complicated two-dimensional , three-dimensional networks.








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