# Thallide

Thallides are compounds containing anions composed of thallium. There are several thallium atoms in a cluster, and it does not occur as a single Tl$^−$ in thallides. They are a subclass of trielides, which also includes gallides and indides. A more general classification is polar intermetallics, as clusters contain delocalized multicentre bonds. Thallides were discovered by Eduard Zintl in 1932.
Mixed anion compounds with thallides include halides (bromides and chlorides), oxides, and tetrelates (silicate, germanate).

## Production

Thallide compounds can be produced by melting metals together in a tantalum crucible under an inert argon atmosphere. However if arsenic is included in the mix, it can react with the crucible wall.
A low temperature production route, is to dissolve an alkali metal in liquid ammonia, and use that to reduce a thallium salt, like thallium iodide.

## Properties

Thallide compounds are dense, dense to X-rays and usually metallic grey or black in appearance.
Thallide clusters mostly do not follow Wade-Mingos rules or the Zintl–Klemm concept, as they have too small a negative charge. They can be called "hypoelectronic".

## Reactions

In liquid ammonia, oxidation occurs yielding metal amides, and thallium metal.
Thallides react with water and air.

## List

| formula | system | space group | unit cell | volume | density | comment |
| LiTl | cubic | Pm3m | a=3.43 | | | melts at 508 °C |
| Li$_2$Tl | orthorhombic | Cmcm | a=4.741 b=10.023 c=4.786 | | | decomposes at 381 °C |
| Li$_5$Tl$_2$ | | R3m | a=4.716 c=20.399 | | | melts at 448 °C |
| Li$_3$Tl | cubic | Fm3m | a=6.67 | | | melts at 447 °C |
| Li$_{22}$Tl$_5$ (Li$_4$Tl) | cubic | F43m | a=20.003 | | | |
| NaTl | cubic | Fd3m | | | | 3D diamond structure mesh for Tl; melts at 305 °C |
| NaTl | tetragonal | I4$_1$/amd | a=5.2341 c=7.5290 Z=4 | 206.26 | | grey; |
| Na$_2$Tl | orthorhombic | C222$_1$ | a=13.9350 b=8.8797 c=11.6927 | | | [Tl$_4$]$^{8–}$ tetrahedra; melts at 154 °C |
| NaTl$_2$ | | | | | | decomposes at 154 °C |
| Na$_6$Tl | cubic | F43m | a=24.154 | | | melts at 77.4 |
| KTl | orthorhombic | Cmca | a=15.239 b=15.069 c=8.137 | | | [Tl$_6$]$^{6–}$ Compressed octahedra; melts incongruently at 268 °C |
| K$_5$Tl$_8$ | | | | | | melts at 273 °C |
| K$_{10}$Tl$_7$ | monoclinic | P2$_1$/c | a = 10.132 b = 22.323 c = 13.376 β = 93.14° Z=4 | | | [Tl$_7$]$^{7–}$ pentagonal bipyramid |
| K$_{10}$Tl$_6$O$_2$ | | | | | | [Tl$_6$]$^{6–}$ |
| K$_8$Tl$_{11}$ | rhombohedral | R3c | a=9.991 c=5.084 | | | [Tl$_{11}$]$^{7–}$ pentacapped trigonal prism; melts at 320 °C |
| K$_{49}$Tl$_{108}$ | | Pm3 | a = 17.28.7 Z=1 | | | |
| K$_5$Tl$_{17}$ | orthorhombic | Cccm | | | | |
| K$_6$Tl$_{17}$ | orthorhombic | Cccm | a = 16.625 b = 23.594 c = 15.369 Z = 8 | 6028 | 8.173 | @22 °C; metallic; ρ$_{270}$ = 22.6 μΩ·cm, α = 0.0023 K$^{−1}$ |
| K$_{10}$Tl$_6$O$_2$ | orthorhombic | Cmcm | a=8.3755 b=32.102 c=8.8634 Z=4 | 2383.1 | 4.597 | dark grey |
| Na$_7$KTl$_4$ | orthorhombic | Pbam | a=16.2860 c=11.2771 Z=8 | 2991.1 | 4.519 | [Tr$_4$]$^{8−}$ |
| Na$_9$K$_{16}$Tl$_{~25}$ | | | | | | |
| [Et$_4$N]$_2$[{Tl(Fe(CO)$_4$)$_2$}$_2$] | | | | | | |
| [(PPh$_2$)$_2$N]$_2$[Tl$_2$Fe$_6$(CO)$_{24}$] | monoclinic | P2$_1$/c | a=17.120 b=50.71 c=16.785 β=116.90° | | | |
| [Et$_4$N]$_4$[Tl$_4$Fe$_8$(CO)$_{30}$] | | | | | | |
| [Et$_4$N]$_6$[Tl$_6$Fe$_{10}$(CO)$_{36}$] | | | | | | |
| K$_8$ZnTl$_{10}$ | | | | | | band gap 0.17 eV |
| K$_8$GaTl$_{10}$ | tetragonal | P4/nnc | a=10.1858 c=13.6371 Z=2 | 1414.9 | 5.695 | |
| K$_{49}$Ga$_2$Tl$_{108}$ | | | | | | |
| Rb$_8$Tl$_{11}$ | | | | | | [Tl$_{11}$]$^{7–}$ pentacapped trigonal prism |
| Rb$_{15}$Tl$_{27}$ | | P62m | | | | |
| Rb$_{17}$Tl$_{41}$ | hexagonal | Fd3m | a = 10.3248 c = 17.558 | | | |
| Rb$_{10}$Tl$_6$O$_2$ | orthorhombic | Cmcm | a=8.7176 b=33.2934 = 9.1242 | 2648.19 | 5.300 | dark grey; [Tl$_6$]$^{6–}$ |
| Na$_7$RbTl$_4$ | orthorhombic | Pbam | a=16.3584 b=16.3581 c=11.3345 Z=8 | 3033.0 | 4.660 | @123K [Tl$_4$]$^{8−}$ tetrahedra |
| K$_4$Rb$_4$Tl$_{11}$Cl$_{0.1}$ | rhombohedral | R3c | a=10.0948 c=51.027 Z=6 | 4503.3 | 6.087 | |
| Rb$_8$GaTl$_{10}$ | tetragonal | P4/nnc | a=10.4714 c=14.0007 Z=2 | 1535.2 | 6.051 | |
| Rb$_{49}$Ga$_2$Tl$_{108}$ | | | | | | |
| Sr$_3$Tl$_5$ | orthorhombic | Cmcm | a = 10.604 b = 8.675 c = 10.985 Z = 4 | 1010.5 | 8.445 | silvery, brittle; [Tl$_5$]$^{6–}$ square pyramidal clusters |
| YMgTl | hexagonal | P62m | a=7.505 c=4.5985 Z=3 | | 7.05 | metallic; black powder |
| Pd$_3$Tl | tetragonal | I4/mmm | a=4.10659 c=15.3028 Z = 4 | 258.07 | | Palladothallite |
| SrPdTl$_2$ | orthorhombic | Cmcm | a = 4.486 b = 10.991 c = 8.154 Z = 4 | | | |
| Na$_{13}$(Cd$_{~0.70}$Tl$_{~0.30}$)$_{27}$ | cubic | Im3 | a ≃ 15.92 Z = 4 | | | Tl from 0.24 to 0.33 |
| K$_{14}$Cd$_9$Tl$_{21}$ | hexagonal | P2m | a = 9.884 c =17.173 Z = 2 | | | |
| Na$_9$K$_{16}$Tl$_{18}$Cd$_3$ | hexagonal | P6$_3$/mmc | a = 11.136 c = 29.352 Z=2 | | | |
| Rb$_5$Cd$_2$Tl$_{11}$ | orthorhombic | Amm2 | a = 5.5999 b = 17.603 c = 12.896 Z = 2 | | | |
| Na$_{12}$K$_{18}$In$_{53}$Tl$_7$ | | R3m | a=16.846 c=43.339 Z=4 | | | |
| Na$_6$TlSb$_4$ | monoclinic | C2/c | 15.154 b = 10.401 c = 17.413 β = 113.57° Z = 8 | | | metallic |
| K$_6$Tl$_2$Sb$_3$ | monoclinic | C2/c | a = 9.951 b = 17.137 c = 19.640 β = 104.26° Z = 8 | | | |
| CsTl | orthorhombic | Fddd | | | | [Tl$_6$]$^{6–}$ |
| Cs$_{3.45}$K$_{3.55}$Tl$_7$ | tetragonal | I4$_1$/a | a = 13.6177 c = 25.5573 Z = 8 | 4739.3 | 5.681 | [Tl$_7$]$^{7−}$ |
| Cs$_{7.29}$K$_{5.71}$Tl$_{13}$ | monoclinic | C2/c | a = 30.7792 b = 11.000 c = 14.0291 β = 112.676° Z = 4 | 4382.7 | 5.835 | [Tl$_7$]$^{7−}$ and [Tl$_6$]$^{6–}$ |
| K$_{3.826}$Cs$_{4.174}$Tl$_{11}$ | | | | | | |
| Cs$_8$Tl$_{11}$ | | | | | | [Tl$_{11}$]$^{7–}$ pentacapped trigonal prism |
| Cs$_{15}$Tl$_{27}$ | hexagonal | P62m | | | | |
| Cs$_4$Tl$_2$O | trigonal | R3m | a = 11.986 c = 20.370 Z = 9 | 2534.3 | 5.640 | silvery black; stable to 523 °C; decomposes in air |
| Cs$_{18}$Tl$_8$O$_6$ | | | | | | |
| Cs$_{10}$Tl$_6$SiO$_4$ | monoclinic | P2$_1$/c | a=18.9121 b=11.4386 c=14.8081 β=90.029° | | | [Tl$_6$]$^{6–}$ |
| Cs$_{10}$Tl$_6$GeO$_4$ | monoclinic | P2$_1$/c | a=19.034 b=11.4883 c=14.8633 β=90.033° | | | [Tl$_6$]$^{6–}$ |
| Cs$_{10}$Tl$_6$SnO$_3$ | orthorhombic | Pnma | a=14.8908Å b=19.052 c=11.5855 | | | [Tl$_6$]$^{6–}$ |
| Rb$_{14}$CsTl$_{27}$ | hexagonal | | | | | |
| Cs$_8$GaTl$_{10}$ | tetragonal | P4/nnc | a=10.777 c=14.354 Z=2 | 1667.3 | 6.328 | |
| Cs$_5$Cd$_2$Tl$_{11}$ | orthorhombic | Amm2 | a = 5.6107 b = 18.090 c = 13.203 Z = 2 | | | |
| Cs$_8$Tl$_{11}$Pd$_{0.84}$ | rhombohedral | R3c | a = 10.6l0 c = 54.683 Z = 6 | | | |
| Cs$_8$Tl$_{11}$Cl$_{0.8}$ | rhombohedral | R3c | a=10.4691 c=53.297 Z = 6 | 5058.8 | 6.578 | |
| Cs$_8$Tl$_{11}$Br$_{0.9}$ | rhombohedral | R3c | a=10.5608 c=53.401 Z = 6 | 5157.9 | 6.539 | |
| Cs$_5$Rb$_3$Tl$_{11}$Cl$_{0.5}$ | rhombohedral | R3c | a=10.3791 c=52.437 Z = 6 | 4892.0 | 6.502 | |
| Cs$_{5.7}$K$_{2.3}$Tl$_{11}$Cl$_{0.6}$ | rhombohedral | R3c | a=10.3291 c=51.909 Z = 6 | 4796.3 | 6.469 | |
| BaTl$_2$ | hexagonal | P6$_3$/mmc | | | | |
| BaTl$_4$ | monoclinic | C2/m | a = 12.408 b = 5.351 c = 10.383 β = 116.00° Z = 4 | 519.6 | | silvery |
| LaMgTl | hexagonal | P62m | a=7.813 c=4.7784 Z=3 | | 7.25 | metallic; black powder |
| CeMgTl | hexagonal | P62m | a=7.741 c=4.7375 Z=3 | | 7.47 | metallic; black powder |
| PrMgTl | hexagonal | P62m | a=7.702 c=4.7150 Z=3 | 242.9 | 7.60 | metallic; black powder |
| NdMgTl | hexagonal | P62m | a=7.666 c=4.6945 Z=3 | 242.9 | 7.74 | metallic; black powder |
| SmMgTl | hexagonal | P62m | a=7.603 c=4.6593 Z=3 | | 8.10 | metallic; black powder |
| EuTl$_2$ | | | | | | |
| EuPdTl$_2$ | orthorhombic | Cmcm | a=4.466 b=10.767 c=8.120 Z=4 | 3905 | 11.35 | silvery metallic |
| GdMgTl | hexagonal | P62m | a=7.556 c=4.6312 Z=3 | 229.9 | 7.74 | metallic; black powder |
| TbMgTl | hexagonal | P62m | a=7.518 c=4.6088 Z=3 | 226.7 | 8.52 | metallic; black powder |
| DyMgTl | hexagonal | P62m | a=7.495 c=4.5932 Z=3 | 224.1 | 8.69 | metallic; black powder |
| HoMgTl | hexagonal | P62m | a=7.471 c=4.5835 Z=3 | | | metallic; black powder |
| ErMgTl | hexagonal | P62m | a=7.449 c=4.5715 Z=3 | | | metallic; black powder |
| TmMgTl | hexagonal | P62m | a=7.432 c=4.5541 Z=3 | | | metallic; black powder |
| LuMgTl | hexagonal | P62m | a=7.402 c=4.5400 Z=3 | | | metallic; black powder |
| K$_5$TaAs$_4$Tl$_2$ | orthorhombic | Pnma | | | | |
| Rb$_5$TaAs$_4$Tl$_2$ | orthorhombic | Pnma | a = 19.196 b = 11.104 c = 7.894 Z = 4 | | | spiro at Ta |
| SrPtTl$_2$ | orthorhombic | Cmcm | a = 4.491 b = 10.990 c = 8.140 Z = 4 | | | |
| Na$_{12}$K$_{38}$Tl$_{48}$Au$_2$ | | | | | | Tl$_7$ and Tl$_9$ cluster + auride |
| K$_3$Au$_5$Tl | orthorhombic | Imma | a = 5.595 b =19.706 c =8.430 Z = 4 | | | |
| Rb$_2$Au$_3$Tl | orthorhombic | Pmma | a = 5.660 b = 6.741 c = 9.045 Z = 4 | | | |
| BaAuTl$_3$ | tetragonal | I4/mmm | a = 4.8604 c = 12.180 Z = 2 | | | |
| Ba$_2$AuTl$_7$ | orthorhombic | Pmma | a=21.919 b=5.193 c=10.447 | | | |
| BaAu$_{0.40}$Tl$_{1.60}$ | orthorhombic | Imma | a = 5.140 b = 8.317 c = 8.809 Z = 4 | | | |
| BaHg$_{0.80}$Tl$_{3.20}$ | monoclinic | C2/m | a=12.230 b=5.234 c=10.379 β = 115.272 | 600.3 | 10.523 | silvery |