The syntheses and X-ray single-crystal low-temperature structures of the four new ammoniates [Li(NH 3 ) 4 ] 3 As 7´N H 3 (1), ] 3 As 7´8 NH 3 (2), Cs 3 As 7´6 NH 3 (3), and (Ph 4 P) 2 CsAs 7´5 NH 3 (4) are reported. The compounds were obtained by either direct reduction of As with Li/Cs in liquid NH 3 , solvation of Cs 4 As 6 /Rb 4 As 6 in liquid NH 3 , or by extraction of solid Cs 3 As 7 . While compound 1 contains isolated As 3À 7 polyanions, AsÀM contacts (M Na À Cs) lead to neutral 2À chains in 4, respectively.

Structure D 2000Syntheses and Crystal Structures of Four New Ammoniates with Heptaarsenide ) Anions. -The structures of the new heptaarsenides (III) (orthorhombic, space group Pna21, Z = 4), (V) (monoclinic, P21/n, Z = 4), (VII) (trigonal, R3c, Z = 18), and (VIII) (monoclinic, P21/c, Z = 4) are determined by single crystal XRD. While compound (III) contains isolated polyanions, As-M contacts (M: Rb, Cs) lead to neutral [Rb(18-crown-6)] 3 As 7 units in (V), a three-dimensional, extended network in (VII), and infinite ] chains in (VIII), respectively. The structure of the As7 unit is analogous to nortricyclane in all four compounds. -(HANAUER, T.; GROTHE, M.; REIL, M.; KORBER*, N.; Helv. Chim. Acta 88 (2005) 5, 950-961; Inst. Anorg. Chem., Univ. Regensburg, D-93053 Regensburg, Germany; Eng.) -Schramke 35-003 (As 3-7

Orangefarbene Kristalle der Titelverbindung [Co(NH3)6]2As12Se4 · 12 NH3 wurden durch Reduktion von As4Se4 mit einer Natriumlösung in flüssigem Ammoniak und anschließendes Ausfällen mit CoBr2 gewonnen. Eine Einkristallstrukturanalyse ergibt als anionischen Baustein das Selenoarsenat As12Se44—, welches aus einem zentralen As12‐Käfig besteht, an den exo‐ständig vier formal negativ geladene Selenatome gebunden sind. Die Struktur des As12‐Käfigs entspricht sowohl der zentralen Baueinheit eines bekannten Organopolyphosphans als auch der des tubularen P12‐Stranges in der Verbindung (CuI)3P12.

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