Abstract. Powder samples as well as red and transparent single crystals of the Zintl phase Cs 7 NaSi 8 were synthesized and characterized by means of X-ray diffraction and differential thermal analysis. Cs 7 NaSi 8 was found to be isotypic to the recently reported phase Rb 7 NaSi 8 . It crystallizes in the Rb 7 NaGe 8 structure type forming trigonal pyramidal Si 4 4-anions. Two unique environments of the cations are observed, a linear arrangement [Na(Si 4 ) 2 ]7-with short Na-Si distances of 3.0 Å and a Cs2 atom coordinated by six Si 4 4-anions with long Cs-Si distances of 4.2 Å. The bonding situation was investigated by a combined application of 29 Si, 23 Na, and 133 Cs solid-state NMR spectroscopy and quantum mechanical calculations of the NMR coupling parameters. In addition the electronic density of states (DOS),

Powder samples of the title Zintl phase are obtained from a stoichiometric mixture of Cs4Si4 and Na4Si4 (Ta ampule, 500 °C, 14 d).

Crystals and powder of AgNa(VO2F2)2 (I) are prepared by hydrothermal synthesis of a stoichiometric mixture of Ag2O, NaF, and V2O5 in aqueous HF (autoclave, 150°C, 24 h, 40% yield). A Li analog is prepared in the same way. (I) is also obtained both as a powder via boiling in HF (100°C, 3 h, ) and as nanoneedles via hand milling of the reaction components at ambient temperature (settling at 25°C for 3 weeks). (I) crystallizes in the space group P2/c (single crystal XRD) and consists of trioxovanadium fluoride octahedra that combine to form one-dimensional chain-like basic building units as in wolframite. The 1D chains are stacked to create 2D layers which are occupied by Ag + and Na + . The VO3F3 octahedra are ordered according to the different polarizability of Ag + and Na + . With (I) as a baseline compound, new material design rules for emerging Na + ion systems are identified which provide appreciable voltages for sodium ion electrochemistry. -(DONAKOWSKI, M. D.; GOERNE, A.; VAUGHEY, J. T.; POEPPELMEIER*, K. R.; J. Am. Chem. Soc. 135 (2013) 26, 9898-9906, http://dx.doi.org/10.1021/ja404189t ; Dep. Chem., Northwest. Univ., Evanston, IL 60208, USA; Eng.) -J. Schramke 42-022