SYNTHESIS AND CRYSTAL-STRUCTURE OF TRICAESIUM HEPTAPHOSPHIDE-AMMONIA(1 3)CS3P7-CENTER-DOT-3 NH3/

Recrystallization of Cs3P7 from liquid NH3 yields the triammoniate Cs3 P7 . 3 NH3, which loses the weakly bound NH3 of crystallization below 253 K. A low-temperature crystal-structure analysis shows that Cs3P7 . 3 NH3 consists of a framework of heptaphosphanortricyclane anions P-7 (3-) and Cs+ cations with NH3 molecules completing the coordination of the cations. The framework is built from Cs3P7 layers connected by on ly few Cs - P interactions, the interlayer gap being filled by a two-d imensional network of NH3. The Cs7P7 part of the structure completes a family of alkali-metal-polyphosphide substructures which range from ( 1)(infinity)[RbP7](2-) or (1)(infinity)[CsP11](2-) chains over (2)(inf inity)[Cs2Pn](-) layers (n = 7, 11) to now (3)(infinity)[Cs3P7] framew orks.