Manganese(II) Coordination Polymers [{Mn(tren)}(As 2 Se 4 )] and [{Mn(tren)}(As 4 Se 7 )] with Infinite Selenidoarsenate(III) Chains $^{1}_{\infty}\rm [AsSe_{2}^{-}]$ and $^{1}_{\infty}\rm [As_{4}Se_{7}^{2-}]$

Solvothermal reaction of [MnCl 2 (tren)] with elemental As and Se at 1:1:2 and 1:6:12 molar ratios in H 2 O/tren (10:1) affords the 1D coordination polymers [{Mn(tren)}(As 2 Se 4 )] ( 1 ) and [{Mn(tren)}(As 4 Se 7 )] ( 2 ), respectively. 1 contains vierer infinite $^{1}_{\infty}\rm [AsSe_{2}^{-}]$ chains, which coordinate [(tren)Mn] 2+ fragments through every second terminal Se atom of their corner‐sharing pyramidal AsSe 3 building units. The $^{1}_{\infty}\rm [As_{4}Se_{7}^{2-}]$ double chains of compound 2 are related to the $^{1}_{\infty}\rm [AsSe_{2}^{-}]$ chains 1 by a simple rearrangement of the connectivity pattern between the participating AsSe 3 pyramids and contain condensed centrosymmetric As 8 Se 8 and As 4 Se 4 rings.