Heteropolyanions containing two different heteroatoms. Part III. Cobalto(II)undecatungstophosphate and related anions

Abstract

Salts of the heteropolyanions PCo^IIW₁₁O₄₀H₂^5–, AsCo^IIW₁₁O₄₀H₂^5–, BCo^IIW₁₁O₄₀H₂^7–, BCo^IIIW₁₁O₄₀H₂^6–, and PZnW₁₁O₄₀H₂^5– have been prepared. In the case of the first four and of PNi^IIW₁₁O₄₀H₂^5– there is spectroscopic evidence that the constitutional water is present as an actual water molecule and is replaceable by, e.g., a molecule of pyridine or a substituted pyridine. Replacement of water is fast for the cobalt(II) complexes and slow for BCo^IIIW₁₁O₄₀H₂^6–. Some crystalline salts of derivatives such as PCo^II(C₅H₅N)W₁₁O₃₉^5– have been prepared.

The diffuse reflectance spectra of the cobalt(II) complexes are cation-dependent in the 17,000–20,000 cm^–1 region. Salts whose reflectance and solution spectra differ markedly are dichroic; distortion of the CoO₆ chromophore by crystal packing is accompanied by preferential orientation of the heteropolyanion. Such salts should be suitable for X-ray studies of the detailed structure of the anion.