Carbide bromide

Carbide bromides are mixed anion compounds containing bromide and carbide anions. Many carbide bromides are cluster compounds, containing on, two or more carbon atoms in a core, surrounded by a layer of metal atoms, encased in a shell of bromide ions. These ions may be shared between clusters to form chains, double chains or layers.^[1]

The great majority of these carbide bromide compounds contain rare earth elements. Since these elements have similar properties, similar structures can be made by substituting the elements. R₂CBr₂ forms a structure with layers of R₆C clusters that contain one carbon atom. Each layer has bromide coating the top and bottom. Very similar is R₂CBr₂ which has layers of R₆C₂ clusters containing pairs of carbon atoms. This dicarbon is an ethenide (C₂⁴⁻), and contains a double bond. Layers have bromide on both sides, and so they are only weakly held together by van der Waals forces. If these layers are aligned with each other a 1T- form results with a small c measurement on the unit cell. In some compounds the layers are not quite aligned, but repeat after three layers giving a 3R form, with a larger c unit cell height. Where the layers align, the crystal system is trigonal. But if the layers never quite align at any height, a monoclinic crystal results. The C₂ unit sits at an angle to the layers, and thus reduces symmetry compared to compounds with single carbon atoms in the cluster.^[1]

In R₂CBr there are layers of R₆C that share bromide between layers.^[1]

List

formula	system	space group	unit cell	volume	density	comment	reference
Sc7CBr12	trigonal	R3	a=13.628, c=9.203		4.33		[2]
Y2CBr2	trigonal	R3m	a=3.7545, c=29.125		4.90	bronze	[2]
Y2C2Br2	monoclinic	C12/m1	a=6.953, b=3.764, c=9.938, β=99.98		3.85	superconductor Tc=5.04K	[2][3]
Y2C0.7Br2	trigonal	P3m1	a=3.73 c=9.864		4.83	grey	[2]
Y10Br18(C2)2	monoclinic	P21/n	a=9.729 b=16.323 c=13.229 β =121.131° Z=24	1798.3		black	[4]
Na0.23Y2C2Br2	monoclinic	C2/m	a=7.061, b=3.724, c=10.464, β=92.96		4.43	copper red	[5]
Zr6CBr14	orthorhombic	Cmce	a=14.69 b=13.229 c=11.991				[2]
NaZr6CBr14	orthorhombic	Cmca	a=14.6876, b=13.2266, c=11.9864				[5]
K4Zr6Br18C	triclinic	P1	a=10.114, b=10.283, c=10.374, α=118.54, β=99.98, γ=104.08, Z=1				[6]
RbZr6CBr14	orthorhombic	Cmca	a=14.719, b=13.287, c=12.043				[5]
Cs2Zr6Br10C	trigonal	R3c	a=13.0862 c=35.823 Z=6	5312.8			[7]
CsZr6Br9C	trigonal	R3c	a=13.1031 c=35.800 Z=6	5321.5			[7]
Cs3Zr6Br15C	trigonal	R3c	a=13.116 c=35.980 Z=6				[7]
Cs4Zr6Br15C	trigonal	R3c	a=13.098 c=35.756 Z=6	5312			[7]
La2C2Br	monoclinic	C12/c1	a=15.313, b=4.193, c=6.842, β=100.53,90		5.87		[8]
La3CBr5	monoclinic	C12/c1	a=14.234, b=10.858, c=14.588, β =106.8		5.10	yellow	[8]
La3C2Br3	orthorhombic	C2221	a=11.533, b=17.0698, c=17.054		5.38	bronze	[8]
La4C2Br5	orthorhombic	Immm	a = 3.9950, b = 8.277, c = 18.101		5.43	black	[9]
La5C2Br9	orthorhombic	Pnma	a=11.309, b=9.9477, c=16.4911		5.15	red	[2]
La5C6Br3	monoclinic	C12/m1	a=22.809, b=3.9855, c=16.599, β=123.32		5.30	bronze	[2]
La6C2Br9	monoclinic	C2/c	a=14,234 b=10.858 c=14.588 β=106.80 Z=4	2158.4	4.85	yellow insulator	[10]
La10(C2)6Br6	monoclinic	C2/m	a = 22.809, b = 3.9855, c = 16.599, β = 123.32° Z=2	1260.9	5.301	bronze; air sensitive	[11]
La3Br2C2B		Pnma	f =15.323, b = 3.973, c =11.567			black	[12]
Ce2C2Br	monoclinic	C2/c	a = 15.120, b = 4.179, c = 6.743, β = 101.09 °				[13]
Ce4CBr5	monoclinic	C2/m	a = 18.306, b = 3.9735, c = 8.378, β=104.91°				[14]
Ce4C1.5Br5	monoclinic	C2/m	a = 18.996, b = 3.9310, c = 8.282, β = 106.74°				[14]
Ce4C2Br5	orthorhombic	Immm	a = 3.9835, b = 8.186, c = 18.017		5.54	violet	[9]
Ce4Br3C4	triclinic	P 1	a = 4.227, b = 11.034, c = 11.268, α = 77.15°, β = 90.13° and γ = 84.42°				[15]
Ce10(C2)6Br6	monoclinic	C2/m	a = 22.483, b = 3.9253, c = 16.375, β = 123.15° Z=2	1209.9	5.558	bronze; air sensitive	[11]
Ce6Br3C3B2	monoclinic	P21/m	a = 8.602, b = 3.829, c = 10.220, β = 112.53			black	[12]
Pr2CBr	hexagonal	P63/mmc	a=3.8071, c=14.7787		6.69	black	[2]
Pr2C2Br	monoclinic	C12/c1	a=15.054, b=4.139, c=6.713, β=101.08		6.24		[2]
Pr3CBr3	cubic	I4131	a=11.61		5.73		[2]
Pr3CBr5	triclinic	P1	a=7.571, b=9.004, c=9.062, α=108.57, β=97.77, γ=106.28		5.09	black	[2]
Pr4C1.3Br5	monoclinic	C2/m	a = 18.467, b = 3.911, c = 8.258, β = 105.25°				[14]
Pr4C1.5Br5	monoclinic	C2/m	a = 19.044, b = 3.9368, c = 8.254, β = 106.48°				[14]
Pr5C2Br8	triclinic	P1	a=9.096, b=12.185, c=16.688, α=79.57, β=89.86, γ=84.38		5.02	black	[2]
Pr5C2Br9	monoclinic	P21/n	a = 10.069; b = 18.861; c = 10.459; β = 108.130° Z = 4		5.09	dark red	[2]
Pr5C6Br3	monoclinic	C12/m1	a=22.36, b=3.895, c=16.269, β=90,123.44		5,71		[2]
Pr6C2Br10	triclinic	P1	a=7.571 b=9.004 c=9.062 α=108.57° β=97.77° γ=106.28° Z=1	544.8	5.09	black	[16]
Pr7C3Br10			a=9.054, b=11.1265, c=13.352, α=79.641, β=72.57, γ=64.67		5.22	black	[2]
Pr10C4Br15	triclinic	P1	a=9.098 b=10.127 c=10.965 α=70.38° β=66.31° γ=70.84° Z=1	849.3	5.19	silver	[16]
Pr10(C2)2Br16	triclinic	P1	a = 9.096, b = 12.185, c = 16.688, α = 79.57°, β = 89.86°, γ = 84.38°			metallic black	[17]
Pr10(C2)6Br6	monoclinic	C2/m	a = 22.36, b = 3.895, c = 16.269, β = 123.44° Z=2			bronze; air sensitive	[11]
Pr14C6Br20	triclinic	P1	a=9.098 b=10.935 c=13.352 α=86.27° β=75.57° γ=66.88° Z=1	1157.8	5.23	black	[16]
Pr6C2Cl5Br5	monoclinic	C2/c	a = 13.689(1) Å, b = 10.383(1) Å, c = 14.089(1) Å, β = 106.49(1)°			yellow to green	[18]
Gd2CBr	hexagonal	P63/mmc	a=3.7858, c=14.209		7.65	dark grey	[8]
Gd2Br2C	trigonal	P3m1	a=3.8209, c=9.824			black	[19]
3s-Gd2C2Br2	monoclinic	C2/m	a = 7.066, b = 3.827, c = 9.967, β = 99.95°		5.69	black; contains C24−	[20][21][22]
Gd2C2Br2	monoclinic	C2/m	a=7.025, b=3.8361, c=9.868, β =94.47		6.24	gold	[8]
Gd4C2Br3	orthorhombic	Pnma	a = 10.844, b = 3.730, c = 20.361		6.58	bronze	[23]
Gd10C4Br18	monoclinic	P21/n	a=9.7406 b=16.4817 c=11.8604 β =104.394° Z=24			contains C24−	[4]
Gd10(C2)6Br6	monoclinic	C2/m	a = 21.507, b = 3.7193, c = 15.331, β = 123.34° Z=2	1024.5	6.254	bronze; air sensitive	[11]
Gd4Br3C2B	monoclinic	P21/m	a=9.547, b=3.693, c=12.44,5, β=106.68			black	[12]
K2[Gd10(C2)2]Br19	orthorhombic	Pbcn	a=12.751, b=23.17, c=14.423		5.01	black	[24]
K2[Gd10(C2)2]Br20	orthorhombic	Pbca	a=1.2751, b=2.317, c=1.4423		4.70	black	[24]
Rb2[Gd10(C2)2]Br19	orthorhombic	Pbcn	a=1.2737, b=2.325, c=1.4412		5.15	black	[24]
Cs2[Gd10(C2)2]Br19	orthorhombic						[24]
TbCBr	monolinic	C12/m1	a=7.015, b=3.801, c=9.948, β=100.05		6.28		[2]
Tb2CBr	hexagonal	P63/mmc	a=3.6915, c=14.043		8.21		[2]
Tb2CBrH	hexagonal	P63mc	a=3.7376, c=14.315		7.88		[5]
Tb4C2Br3	orthorhombic	Pnma	a = 10.743, b = 3.706, c = 20.194		7.31	bronze	[23]
Tb10Br18(C2)2	monolinic	P121/c1	a=9.7562 b=16.4254 c=13.3043 β =120.675°	1833.7	5.57	dark red	[4][2]
Rb2[Tb10(C2)2]Br19	orthorhombic		a=1.2664, b=2.3105, c=1.4303			black	[24]
Dy10Br18(C2)2	monolinic	P21/c	a = 9.740 b = 16.340 c = 13.247 β = 120.869° Z = 2	1809.6		black	[25]
Ho10Br18(C2)2	monolinic	P21/n	a=9.6838 b=16.2436 c=11.6374 β =104.427° Z=24	1772.8			[4]
[Er10(C2)2]Br18	monoclinic	P21/n	a = 9.718, b = 16.234, c = 11.638, β = 104.00°; Z = 2		5.89	black	[26]
Lu2CBr2	trigonal	R3m	a= 3.6663, c=28.799		7.75	gold	[2]
La0.9Lu0.1CBr	monoclinic	C2/m	a=7.434, b=4.0568, c=10.046, β=93.7		5.15		[5]
W30C2(Cl,Br)68	triclinic	P1	a = 12.003, b = 14.862, c = 15.792, α = 88.75°, β = 68.85°, γ = 71.19° Z=1	2472.9	6.35	black	[27]
Th6CBr15	orthorhombic	Cmce	a=15.764, b=14.16, c=13.124		5.72	green	[28]
Y0.8Th0.2CBr	monoclinic	C2/m	a=7.061, b=3.776, c=9.983, β=100.36		5.31		[5]