Hydrated Alkali Metal and Ammonium Salts of the [P 2 Se 6 ] 4– Anion

The synthesis and structures of the five new compounds [Na 4 (P 2 Se 6 )(H 2 O) 6 ], [M 4 (P 2 Se 6 )(H 2 O) 4 ] (M = K, Rb, Cs) and [(NH 4 ) 4 (P 2 Se 6 )(H 2 O) 2 ] are reported. The salts were obtained from reactions of metal carbonates with P 4 Se 10 in water and in ambient atmosphere. During the heterogeneous reactions, the selenophosphate salts, CO 2 and elemental selenium is formed together with the [P 2 O 6 ] 4– ion and most likely other phosphate/selenophosphate derivatives. The ethane‐like [P 2 Se 6 ] 4– anion was characterized in solution by 31 P NMR spectroscopy showing an ABX pattern.