Ag3SnCuP10 : [Ag3Sn] tetrahedra embedded between adamantane-type [P-10] cages

Lange S, Sebastian CP, Zhang L, Eckert H, Nilges T

Abstract

Ag3SnCuP10 was synthesized from a stoichiometric mixture of copper, silver, tin, and red phosphorus, with SnI4 added as a mineralization agent. Cubic Ag3SnCuP10, space group F (4) over bar3 m (No. 216) with lattice parameter a = 10.503(1) angstrom and Z = 4, consisting of orientationally disordered [Ag3Sn] heteroclusters and adamantane-type [P-10] cages, is one example in which structure determination was possible only by the combined use of diffraction and spectroscopic methods. An ideal 4-fold domain twin structure that results for a R 3 m model, featuring an ordered arrangement of the heteroclusters, cannot be differentiated from the F (4) over bar 3m model by diffraction methods alone. After a detailed NMR spectroscopic examination using state of the art solid-state NMR techniques, we found the local environment around the [P10] cages of the F (4) over bar3 m model to be the correct description of the Ag3SnCuP10 structure. A possible Cu/Ag or Ag/Sn disorder in the [Ag3Sn] heterocluster and within the copper substructure was excluded by Mossbauer spectroscopic investigations and NMR measurements.