Synthesis and Crystal Structure of Bis(methyltriethylammonium) Hexabromotellurate(IV)‐tris{dibromodiselenate(I)}, [NMeEt3]2n[TeBr6(Se2Br2)3]n, Containing a Chain‐Polymeric Mixed‐valence Bromotellurate(IV)‐Selenate(I) Anion

Abstract

AbstractRed crystals of [NMeEt3]2n[TeBr6(Se2Br2)3]n (1) were isolated when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriethylammonium bromide (1:2). The salt 1 crystallizes in the monoclinic space group C2/c with the cell dimensions a = 27.676(6) Å, b = 9.665(2) Å, c = 18.796(4) Å and ß = 124.96(3)° (120 K). The [TeBr6(Se2Br2)3]2— anions contain nearly regular octahedral [TeBr6]2— ions which are incorporated into a polymeric chain by bonding contacts between 3 facial bromo ligands and 3 Se2Br2 molecules, one of which is situated on the twofold symmetry axis. The distances between the μBr ligands and the SeI atoms of the Se2Br2 molecules are observed in the range 3.308(2) — 3.408(2) Å and can tentatively be interpreted as donor‐acceptor bonds with μBr as donors and Se2Br2 as acceptors. The TeIV—Br distances are in the range 2.669(1) — 2.687(1) Å. The bond lengths in the connecting Se2Br2 molecules are: SeI—SeI = 2.267(2) and 2.281(2) Å, SeI—Br = 2.340(1), 2.353(1) and 2.337(1) Å.