Synthesis and crystal structures of Nd 6Pt 13In 22, Sm 6Pt 12.30In 22.70, and Gd 6Pt 12.48In 22.52

Abstract

The rare earth-platinum-indides Nd 6Pt 13In 22, Sm 6Pt 12.30In 22.70, and Gd 6Pt 12.48In 22.52 were synthesized from the elements by arc-melting of the components. Single crystals were grown using special annealing sequences. The three indides were investigated by X-ray powder and single crystal diffraction: Tb 6Pt 12In 23 type, C2/ m, Z = 2 , a = 2 8 1 1.9 ( 6 ) , b = 4 4 1.6 0 ( 9 ) , c = 1 4 8 6.6 ( 3 ) pm , β = 1 1 2.1 0 ( 3 ) ° , w R 2=0.0629, 3645 F 2 values, 126 variables for Nd 6Pt 13In 22, a = 2 8 2 1.9 ( 6 ) , b = 4 4 3.0 6 ( 9 ) , c = 1 4 8 1.0 ( 3 ) pm , β = 1 1 2.3 9 ( 3 ) ° , w R 2=0.0543, 3679 F 2 values, 127 variables for Sm 6Pt 12.30In 22.70, and a = 2 8 1 8.5 ( 6 ) , b = 4 3 9.9 0 ( 9 ) , c = 1 4 8 0.9 ( 3 ) pm , β = 1 1 2.2 9 ( 3 ) ° , w R 2=0.0778, 3938 F 2 values, 127 variables for Gd 6Pt 12.48In 22.52. Most platinum atoms in these structures have a distorted trigonal prismatic coordination by rare earth metal and indium atoms. Together, the platinum and indium atoms build up a complex three-dimensional [Pt 12+ x In 23− x ] polyanionic network in which the rare earth metal atoms fill distorted pentagonal and hexagonal channels. The 2 c Wyckoff site in these structures plays a peculiar role. This site is occupied by indium in the prototype Tb 6Pt 12In 23, while platinum atoms fill the 2 c site in Nd 6Pt 13In 22, leading to a linear Pt 3 chain with Pt–Pt distances of 275 pm. The crystals with samarium and gadolinium as rare earth metal component show mixed Pt/In occupancies.