TlPO3 and its comparison with isotypic RbPO3 and CsPO3.

Matthias Weil

doi:10.1107/s2056989020011238

Abstract

The crystal structure of thallium(I) catena-polyphosphate, TlPO3, contains a polyphosphate chain extending parallel to [010] with a repeating unit of two phosphate tetra-hedra. The TlI atom is located in-between the polyphosphate chains and is bonded by oxygen atoms in a distorted [6+1] coordination in the form of a monocapped prism, with the longest Tl-O bond to the bridging O atom of the polyphosphate chain. A qu-anti-tative structural comparison with isotypic RbPO3 and CsPO3 reveals that the usually pronounced stereoactivity of the 6s 2 lone pair at the TlI atom is not apparent in the case of TlPO3.

Highlights

Chemical contextThe crystal chemistry of inorganic thallium(I) (or thallous) compounds is dominated by the presence of the 6s2 electron lone pair that, in the majority of cases, is stereochemically active (Galy et al, 1975)
The crystal structure of thallium(I) catena-polyphosphate, TlPO3, contains a polyphosphate chain extending parallel to [010] with a repeating unit of two phosphate tetrahedra
The crystal chemistry of inorganic thallium(I) compounds is dominated by the presence of the 6s2 electron lone pair that, in the majority of cases, is stereochemically active (Galy et al, 1975)

Summary

Chemical context

The crystal chemistry of inorganic thallium(I) (or thallous) compounds is dominated by the presence of the 6s2 electron lone pair that, in the majority of cases, is stereochemically active (Galy et al, 1975). Crystal structures comprising a TlI atom mostly have unique structures, and isotypism with analogous phases where the TlI site is replaced by a metal cation of comparable size or by ammonium is comparatively rare. One of these cases pertains to the catenapolyphosphate series MPO3 (M = Tl, Rb, Cs) for which isotypism of TlPO3 with the alkali polyphosphates was reported on basis of indexed powder X-ray diffraction data (El Horr, 1991). With the intention of obtaining detailed structure data for TlPO3 for a quantitative structural comparison with isotypic RbPO3 and CsPO3, single crystals of the thallium polyphosphate phase were grown and the crystal structure refined using single-crystal X-ray data

Structural commentary

Synthesis and crystallization

Findings

Refinement