Syntheses and Crystal Structures of Four New Ammoniates with Heptaarsenide (As $\rm{_{7}^{3-}}$ ) Anions

The syntheses and X‐ray single‐crystal low‐temperature structures of the four new ammoniates [Li(NH 3 ) 4 ] 3 As 7 ⋅NH 3 ( 1 ), [Rb(18‐crown‐6)] 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 $\rm{_{7}^{3-}}$ polyanions, AsM contacts (M=Na−Cs) lead to neutral [Rb(18‐crown‐6)] 3 As 7 units in 2 , a three‐dimensional, extended network in 3 , and one‐dimensional, infinite $\rm{_{\infty }^{1}}$ [CsAs 7 ] 2− chains in 4 , respectively.