Synthesis and thermal dehydration of hexaaquarhodium(III) phosphates

Complex salts Rh(H₂O)₆]PO₄ (I) and Rh(H₂O)₆]PO₄ · H₂O (II) were obtained. Dehydration processes of compounds I and II were studied by thermogravimetry and differential scanning calorimetry. The heat effect for the loss of 0.82 ± 0.01 H₂O (hydration) molecule was found to be 54 ± 1 kJ/mol, while that for the loss of coordinated H₂O is 47 ± 1 kJ/mol (for I) and 43 ± 1 kJ/mol (for II). The solid phases of dehydration products were studied by X-ray powder diffraction, IR and ³¹P MAS NMR spectroscopy, and they were found to be polymers.