Highly polyhapto–aromatic interactions in thallium(I) coordination

In the solid state, the Tl(I) complex of 4-hydroxybenzoate (HB−), [Tl(HB)]n (1), can be regarded as containing polymeric chains linked through 2 × η6 interactions of the Tl atoms with phenyl groups from adjacent units. The thallium atoms contain close TlI ⋯ π (aromatic) contacts, thus attaining a total hapticity of 16 with environments TlO4C12. The unusually high coordination number in the this compound may reflect the capacity of Tl(I) to act as both a Lewis acid and a Lewis base.