Networks of icosahedra in the sodium–zinc–stannides Na16Zn13.54Sn13.46(5), Na22Zn20Sn19(1), and Na34Zn66Sn38(1)

The three new ternary phases Na16Zn13.54Sn13.46(5) (I), Na22Zn20Sn19(1) (II), and Na34Zn66Sn38(1) (III) were obtained by direct fusion of the pure elements and characterized by single crystal X-ray diffraction experiments: I, Ibam, Z=8, a=27.401(1), b=16.100(1), c=18.431(1) Å, R1/wR2 (all data)=0.051/0.088; II, Pnma, Z=4, a=16.403(1), b=15.598(1), c=22.655(6) Å, R1/wR2 (all data)=0.038/0.071; III, R3¯m, Z=3, a=16.956(1), c=36.861(1) Å, R1/wR2 (all data)=0.045/0.092. The structures consist of complex 3D cluster networks made of Zn and Sn atoms with the common motif of Kagomé nets of icosahedra. Additionally to the new heteroatomic {Zn12−xSnx} icosahedra that are omnipresent, triangular units, cages, and pairs of triply fused icosahedra fill the cavities of the Kagomé nets in compounds I, II, and III, respectively. Whereas I crystallizes in a new structure type, II and III have structural analogs in trielide chemistry. All three compounds closely approach the electron numbers expected for valence compounds according to the extended 8-N rule. The concept of achieving an isovalent situation to triel elements by combination of electron poorer and richer elements and the readily mixing of Zn and Sn allow the formation of icosahedral and triangular clusters without the participation of a group 13 element.

Three new compounds Na16Zn13.54Sn13.46(5) (I), Na22Zn20Sn19(1) (II), and Na34Zn66Sn38(1) (III) were obtained from the elements and were characterized by single-crystal X-ray diffraction. Their structures have in common Kagome layers of {Zn12−xSnx} icosahedra. Additional building units, such as triangles, 15-atom spacer, and triply fused icosahedra fill the structures of I, II, and III, respectively. The structures and the electron requirements are discussed.Figure optionsDownload as PowerPoint slide