Mixed-Valence Thallium(I, III) Bromides The Crystal Structure of α—Tl2Br3

Abstract

Thallium sesquibromide Tl 2 Br 3 is dimorphic. Scarlet coloured crystals of α-Tl 2 Br 3 were obtained by reactions of aqueous solutions of TlBr 3 and Tl 2 SO 4 in agarose gel. In case of rapid crystallisation of hydrous TlBr 3 /TlBr solutions and from TlBr/TlBr 2 melts ß-Tl 2 Br 3 is formed as scarlet coloured, extremely thin lamellae. The crystal structures of both forms are very similar and can be described as mixed-valence thallium(I)-hexabromothallates(III) Tl 3 [TlBr 6 ]. In the monoclinic unit cell of α-Tl 3 [TlBr 6 ] (a ϭ 26.763(7) Å ; b ϭ 15.311(6) Å ; c ϭ 27.375(6) Å ; ß ϭ 108.63(2)°, Z ϭ 32, space gr. C2/c) the 32 Tl III -cations are found in strongly distorted octahedral TlBr 6 groups. The 96 Tl I cations are surrounded either by four or six TlBr 6 groups with contacts to 8 or 9 Br neighbors. Crystals of ß-Tl 3 [TlBr 6 ] by contrast show almost hexagonal metrics Gemischtvalente Thallium(I,III)-bromide. Die Kristallstruktur von α-Tl 2 Br 3InhaltsübersichtThalliumsesquibromid Tl 2 Br 3 ist dimorph. Dunkelrote Kristallblättchen von α-Tl 2 Br 3 wurden durch Umsetzungen von wässrigen Tl 2 SO 4 /TlBr 3 -Lösungen in Agarose-Gel erhalten. β-Tl 2 Br 3 entsteht in Form extrem dünner, roter Lamellen bei raschen Kristallisationen aus wässrigen TlBr/TlBr 3 -Lösungen oder TlBr/ TlBr 2 -Schmelzen. Beide Formen besitzen einen ähnlichen Aufbau; sie sind als gemischtvalente Thallium(I)-hexabromothallate(III) Tl 3 [TlBr 6 ] zu beschreiben. In der monoklinen Elementarzelle von α-Tl 2 Br 3 (a ϭ 26,763(7) Å ; b ϭ 15,311(6) Å ; c ϭ 27,375(6) Å ; β ϭ 108,63(2)°, Z ϭ 32, Raumgruppe C2/c) sind 32 Tl III -Kationen in stark verzerrten, oktaedrischen TlBr 6 -Baugruppen enthalten. Die 96 Tl I -Kationen sind von vier oder sechs TlBr 6 -Baugruppen umgeben und bilden Kontakte zu 8 oder 9 Br-Nachbarn aus. 2675(a ϭ 13.124(4) Å , b ϭ 13.130(4) Å , c ϭ 25.550(7) Å , γ ϭ 119.91(9)°, Z ϭ 12, P2 1 /m). Refinements of the parameters revealed structural disorder of TlBr 6 units, possibly resulting from multiple twinning. Both structures are composed of Tl 2 [TlBr 6 ] Ϫ and Tl 4 [TlBr 6 ] ϩ multilayers, which alternate parallel (001). The structural relationships of the complicated structures of α-and ß-Tl 3 [TlBr 6 ] to the three polymorphous forms of Tl 2 Cl 3 as well as to the structures of monoclinic hexachlorothallates M 3 TlCl 6 (M ϭ K,Rb) and the cubic elpasolites are discussed.

Lone Pair Effect, Structural Distortions, and Potential for Superconductivity in Tl Perovskites

“…By adding more Tl + ions, mixed valence compounds can be synthesized. 5,6 After the cuprates, the next highest T c perovskite superconductor family is based on BaBiO 3 , 7 which has a formal charge of +4 for Bi (which would be 6s 1 ). From a chemical perspective, the correct formula for BaBiO 3 should be Ba 2 Bi 2 O 6 with both Bi 3+ and Bi 5+ present.…”

“…Tl + halides can easily be oxidized to the +3 oxidation state. By adding more Tl + ions, mixed valence compounds can be synthesized. , …”

New thallium iodates—Synthesis, characterization, and calculations of Tl(IO3)3 and Tl4(IO3)6, [Tl+3Tl3+(IO3)6]

“…With respect to mixed-valent thallium compounds, i.e. those that contain Tl + and Tl 3 + , a few compounds have been reported, for example Tl 2 (CrO 4 ) 2 [16], Tl 4 O 3 [17], TlCl 1.805 Br 0.915 [18], Tl 2 Cl 4 [19], TlPd 3 O 4 [20], Tl 2 Cl 3 [21], Tl 3 (OH)(SO 4 ) 2 [22] [27], and Tl 2 Br 3 [28]. Of these Tl 2 (CrO 4 ) 2 , Tl 3 (OH) (SO 4 ) 2 , and Tl 4 O 3 are of particular relevance to our work, since the materials have a crystallographically unique Tl + and Tl 3 + sites.…”

Solubility, Complex Formation, and Redox Reactions in the Tl2O3−HCN/CN-−H2O System. Crystal Structures of the Cyano Compounds Tl(CN)3·H2O, Na[Tl(CN)4]·3H2O, K[Tl(CN)4], and TlI[TlIII(CN)4] and of TlI2C2O4

“…Mixed valence Tl I −Tl III compounds are very common in thallium chemistry. Depending on the Tl m X n stoichiometry, it is convenient to divide these compounds into several groups: Tl 4 X 3 (Tl I 3 [Tl III X 3 ], X = S 2- ), TlX (Tl I [Tl III X 2 ], X = S 2- , Se 2- , CrO 4 2- , N(CH 2 COO) 3- 25b ), Tl 2 X 3 (Tl I 3 [Tl III X 6 ] X = Cl - ,33a Br - 33b ), and TlX 2 (Tl I [Tl III X 4 ], X = Cl - ,29b Br - , CH 3 COO - , CN - , N 3 - 3a ). Many of these mixed valence compounds have been prepared by reaction between thallium(III) oxide and an appropriate HX acid in an aqueous solution followed by precipitation of usually low-soluble thallous salts.…”