Isolated deltahedral clusters of lead in the solid state: synthesis and characterization of Rb 4Pb 9 and Cs 10K 6Pb 36 with Pb 94−, and A 3A′Pb 4 (A=Cs, Rb, K; A′=Na, Li) with Pb 44−

Abstract

The title compounds were synthesized by direct fusion of the corresponding elements in appropriate atomic ratios at 700 °C, and the structures were determined by single-crystal X-ray diffraction. They contain isolated deltahedral clusters of lead with charge of 4−. The clusters in Rb 4Pb 9 and Cs 10K 6Pb 36 are Pb 9 4−. They are nido according to their charge, but their shapes do not always correspond to the classical nido geometry, a monocapped square antiprism. Some are differently distorted tricapped trigonal prisms. The relationship between these different geometries is discussed, and new classification for such clusters is proposed. The A 3A′Pb 4 compounds are isostructural and contain isolated tetrahedra of Pb 4 4−.