Editing Samarium (section)

==Compounds==
{{Main article|Samarium compounds}}

{| class="wikitable" style="text-align: center; font-size: 90%;"
|-
! Formula
! color
! symmetry
! [[space group]]
! No
! [[Pearson symbol]]
! ''a'' (pm)
! ''b'' (pm)
! ''c'' (pm)
! ''Z''
! density, <br/>g/cm<sup>3</sup>
|-
| Sm
| silvery
| trigonal<ref name="sm"/>
| R{{overline|3}}m
| 166
| hR9
| 362.9
| 362.9
| 2621.3
| 9
| 7.52
|-
| Sm
| silvery
| hexagonal<ref name="sm" />
| P6<sub>3</sub>/mmc
| 194
| hP4
| 362
| 362
| 1168
| 4
| 7.54
|-
| Sm
| silvery
| tetragonal<ref name="sm2">{{cite journal |doi=10.1016/0375-9601(91)90346-A |date=1991|page=89 |volume=158 |issue=1–2 |journal=Physics Letters A |title=A new ultra-high pressure phase in samarium |bibcode=1991PhLA..158...89V |last1=Vohra |first1=Y. |last2=Akella |first2=Jagannadham |last3=Weir |first3=Sam |last4=Smith |first4=Gordon S. |url=https://zenodo.org/record/1258493}}</ref>
| I4/mmm
| 139
| tI2
| 240.2
| 240.2
| 423.1
| 2
| 20.46
|-
| SmO
| golden
| cubic<ref name="smox">{{cite journal|last1=Leger|first1=J.|last2=Yacoubi|first2=N.|last3=Loriers|first3=J. |title=Synthesis of rare earth monoxides |journal=Journal of Solid State Chemistry |volume=36 |page=261 |date=1981 |doi=10.1016/0022-4596(81)90436-9 |issue=3 |bibcode=1981JSSCh..36..261L |doi-access=}}</ref>
| Fm{{overline|3}}m
| 225
| cF8
| 494.3
| 494.3
| 494.3
| 4
| 9.15
|-
| Sm<sub>2</sub>O<sub>3</sub>
|
| trigonal<ref name="smo">{{cite journal|doi=10.1016/0022-4596(81)90058-X|last1=Gouteron|date=1981|first1=J.|page=288|volume=38|journal=Journal of Solid State Chemistry|title=Raman spectra of lanthanide sesquioxide single crystals: Correlation between A and B-type structures|issue=3|bibcode=1981JSSCh..38..288G|last2=Michel|first2=D.|last3=Lejus|first3=A. M.|last4=Zarembowitch|first4=J. }}</ref>
| P{{overline|3}}m1
| 164
| hP5
| 377.8
| 377.8
| 594
| 1
| 7.89
|-
| Sm<sub>2</sub>O<sub>3</sub>
|
| monoclinic<ref name="smo" />
| C2/m
| 12
| mS30
| 1418
| 362.4
| 885.5
| 6
| 7.76
|-
| Sm<sub>2</sub>O<sub>3</sub>
|
| cubic<ref name="smo2">{{cite journal |journal=British Ceramic Transactions and Journal|date=1984|volume=83|issue=4|pages=92–98|last=Taylor |first=D. |title=Thermal Expansion Data: III Sesquioxides, M<sub>2</sub>O<sub>3</sub>, with the corundum and the A-, B- and C-M<sub>2</sub>O<sub>3</sub> structures}}</ref>
| Ia{{overline|3}}
| 206
| cI80
| 1093
| 1093
| 1093
| 16
| 7.1
|-
| SmH<sub>2</sub>
|
| cubic<ref name="smh2">{{cite journal|last1=Daou|first1=J.|last2=Vajda|first2=P.|last3=Burger|first3=J.|title=Low temperature thermal expansion in SmH2+x|journal=Solid State Communications|volume=71|page=1145|date=1989|doi=10.1016/0038-1098(89)90728-X|issue=12|bibcode=1989SSCom..71.1145D }}</ref>
| Fm{{overline|3}}m
| 225
| cF12
| 537.73
| 537.73
| 537.73
| 4
| 6.51
|-
| SmH<sub>3</sub>
|
| hexagonal<ref name="smh3">{{cite journal|doi=10.1016/S0925-8388(96)03071-X|last1=Dolukhanyan|date=1997|first1=S.|page=10|volume=253–254|journal=Journal of Alloys and Compounds|title=Synthesis of novel compounds by hydrogen combustion}}</ref>
| P{{overline|3}}c1
| 165
| hP24
| 377.1
| 377.1
| 667.2
| 6
|
|-
| Sm<sub>2</sub>B<sub>5</sub>
| gray
| monoclinic<ref>{{cite journal|doi=10.1007/BF00795346|last1=Zavalii|date=1990|first1=L. V.|page=471|volume=29|journal=Soviet Powder Metallurgy and Metal Ceramics|last2=Kuz'ma|first2=Yu. B.|last3=Mikhalenko|first3=S. I.|title=Sm2B5 boride and its structure|issue=6|s2cid=138416728}}</ref>
| P2<sub>1</sub>/c
| 14
| mP28
| 717.9
| 718
| 720.5
| 4
| 6.49
|-
| SmB<sub>2</sub>
|
| hexagonal<ref name="smb2">{{cite journal|doi=10.1016/0022-5088(77)90221-1|last1=Cannon|date=1977|first1=J.|page=83|volume=56|journal=Journal of the Less Common Metals|last2=Cannon|first2=D.|last3=Tracyhall|first3=H.|title=High pressure syntheses of SmB2 and GdB12}}</ref>
| P6/mmm
| 191
| hP3
| 331
| 331
| 401.9
| 1
| 7.49
|-
| SmB<sub>4</sub>
|
| tetragonal<ref>{{cite journal|last1=Etourneau|doi=10.1016/0022-5088(79)90038-9|first1=J.|date=1979|page=531|volume=67|last2=Mercurio|journal=Journal of the Less Common Metals |first2=J. |last3=Berrada |first3=A. |last4=Hagenmuller |first4=P. |last5=Georges |first5=R. |last6=Bourezg |first6=R. |last7=Gianduzzo |first7=J.|title=The magnetic and electrical properties of some rare earth tetraborides|issue=2}}</ref>
| P4/mbm
| 127
| tP20
| 717.9
| 717.9
| 406.7
| 4
| 6.14
|-
| SmB<sub>6</sub>
|
| cubic<ref name="smb6">{{cite journal|doi=10.1111/j.1151-2916.1972.tb11344.x|last1=Solovyev|first1=G. I.|date=1972|page=475|volume=55|journal=Journal of the American Ceramic Society|last2=Spear|first2=K. E.|title=Phase Behavior in the Sm-B System|issue=9}}</ref>
| Pm{{overline|3}}m
| 221
| cP7
| 413.4
| 413.4
| 413.4
| 1
| 5.06
|-
| SmB<sub>66</sub>
|
| cubic<ref>{{cite journal|last1=Schwetz|first1=K.|last2=Ettmayer|first2=P.|last3=Kieffer|first3=R.|last4=Lipp|first4=A.|title=Über die Hektoboridphasen der Lanthaniden und Aktiniden|journal=Journal of the Less Common Metals|volume=26|page=99|date=1972|doi=10.1016/0022-5088(72)90012-4}}</ref>
| Fm{{overline|3}}c
| 226
| cF1936
| 2348.7
| 2348.7
| 2348.7
| 24
| 2.66
|-
| Sm<sub>2</sub>C<sub>3</sub>
|
| cubic<ref name="smc" />
| I{{overline|4}}3d
| 220
| cI40
| 839.89
| 839.89
| 839.89
| 8
| 7.55
|-
| SmC<sub>2</sub>
|
| tetragonal<ref name="smc">{{cite journal|doi=10.1021/ja01550a017|last1=Spedding|date=1958|first1=F. H.|page=4499|volume=80|journal=Journal of the American Chemical Society|last2=Gschneidner|first2=K.|last3=Daane|first3=A. H.|title=The Crystal Structures of Some of the Rare Earth Carbides|issue=17|bibcode=1958JAChS..80.4499S }}</ref>
| I4/mmm
| 139
| tI6
| 377
| 377
| 633.1
| 2
| 6.44
|-
| SmF<sub>2</sub>
| purple<ref name="g1241" />
| cubic<ref name="smf2">{{cite journal|last1=Greis|first1=O.|title=Über neue Verbindungen im system SmF2_SmF3|journal=Journal of Solid State Chemistry|volume=24|page=227|date=1978|doi=10.1016/0022-4596(78)90013-0|issue=2|bibcode=1978JSSCh..24..227G }}</ref>
| Fm{{overline|3}}m
| 225
| cF12
| 587.1
| 587.1
| 587.1
| 4
| 6.18
|-
| SmF<sub>3</sub>
| white<ref name="g1241" />
| orthorhombic<ref name="smf2" />
| Pnma
| 62
| oP16
| 667.22
| 705.85
| 440.43
| 4
| 6.64
|-
| SmCl<sub>2</sub>
| brown<ref name="g1241" />
| orthorhombic<ref name="smcl2">{{cite journal|doi=10.1016/0022-5088(86)90228-6|last1=Meyer|first1=G.|date=1986|page=187|volume=116|journal=Journal of the Less Common Metals|last2=Schleid|first2=T.|title=The metallothermic reduction of several rare-earth trichlorides with lithium and sodium}}</ref>
| Pnma
| 62
| oP12
| 756.28
| 450.77
| 901.09
| 4
| 4.79
|-
| SmCl<sub>3</sub>
| yellow<ref name="g1241" />
| hexagonal<ref name="smf2" />
| P6<sub>3</sub>/m
| 176
| hP8
| 737.33
| 737.33
| 416.84
| 2
| 4.35
|-
| SmBr<sub>2</sub>
| brown<ref name="g1241" />
| orthorhombic<ref name="smbr2">{{cite journal |journal=Revue de chimie minérale.|title=Revue für anorganic Chemie|date=1973|volume=10|pages=77–92|author=Bärnighausen, H.}}</ref>
| Pnma
| 62
| oP12
| 797.7
| 475.4
| 950.6
| 4
| 5.72
|-
| SmBr<sub>3</sub>
| yellow<ref name="g1241" />
| orthorhombic<ref name="smbr3">{{cite journal|last1=Zachariasen|first1=W. H.|title=Crystal chemical studies of the 5f-series of elements. I. New structure types|journal=Acta Crystallographica|volume=1|page=265|date=1948|doi=10.1107/S0365110X48000703|issue=5|doi-access=|bibcode=1948AcCry...1..265Z }}</ref>
| Cmcm
| 63
| oS16
| 404
| 1265
| 908
| 2
| 5.58
|-
| SmI<sub>2</sub>
| green<ref name="g1241">[[#Greenwood|Greenwood]], p. 1241</ref>
| monoclinic
| P2<sub>1</sub>/c
| 14
| mP12
|
|
|
|
|
|-
| SmI<sub>3</sub>
| orange<ref name="g1241" />
| trigonal<ref name="smI3">{{cite journal|title=Preparation and Crystal Data for Lanthanide and Actinide Triiodides|last1=Asprey|first1=L. B.|last2=Keenan|first2=T. K.|last3=Kruse|first3=F. H.|journal=Inorganic Chemistry|volume=3|page=1137|date=1964|doi=10.1021/ic50018a015|issue=8|url=https://digital.library.unt.edu/ark:/67531/metadc867868/m2/1/high_res_d/4067674.pdf}}</ref>
| R{{overline|3}}
| 63
| hR24
| 749
| 749
| 2080
| 6
| 5.24
|-
| SmN
|
| cubic<ref name="smn">{{cite journal|last1=Brown|first1=R.|title=Composition limits and vaporization behaviour of rare earth nitrides|journal=Journal of Inorganic and Nuclear Chemistry|volume=36|page=2507|date=1974 |doi=10.1016/0022-1902(74)80462-8|issue=11|last2=Clark|first2=N. J.}}</ref>
| Fm{{overline|3}}m
| 225
| cF8
| 357
| 357
| 357
| 4
| 8.48
|-
| SmP
|
| cubic<ref name="smp">{{cite journal|last1=Meng|first1=J.|title=Studies on the electrical properties of rare earth monophosphides|journal=Journal of Solid State Chemistry|volume=95|page=346|date=1991 |doi=10.1016/0022-4596(91)90115-X|issue=2|bibcode=1991JSSCh..95..346M|last2=Ren|first2=Yufang }}</ref>
| Fm{{overline|3}}m
| 225
| cF8
| 576
| 576
| 576
| 4
| 6.3
|-
| SmAs
|
| cubic<ref name="smas">{{cite journal|last1=Beeken|first1=R.|last2=Schweitzer|first2=J.|title=Intermediate valence in alloys of SmSe with SmAs|journal=Physical Review B|volume=23|page=3620|date=1981|doi=10.1103/PhysRevB.23.3620|issue=8|bibcode=1981PhRvB..23.3620B }}</ref>
| Fm{{overline|3}}m
| 225
| cF8
| 591.5
| 591.5
| 591.5
| 4
| 7.23
|}

===Oxides===
The most stable oxide of samarium is the [[sesquioxide]] Sm<sub>2</sub>O<sub>3</sub>. Like many samarium compounds, it exists in several crystalline phases. The trigonal form is obtained by slow cooling from the melt. The melting point of Sm<sub>2</sub>O<sub>3</sub> is high (2345&nbsp;°C), so it is usually melted not by direct heating, but with [[induction heating]], through a radio-frequency coil. Sm<sub>2</sub>O<sub>3</sub> crystals of monoclinic symmetry can be grown by the flame fusion method ([[Verneuil process]]) from Sm<sub>2</sub>O<sub>3</sub> powder, that yields cylindrical boules up to several centimeters long and about one centimeter in diameter. The boules are transparent when pure and defect-free and are orange otherwise. Heating the metastable trigonal Sm<sub>2</sub>O<sub>3</sub> to {{convert|1900|C|F}} converts it to the more stable monoclinic phase.<ref name="smo" /> Cubic Sm<sub>2</sub>O<sub>3</sub> has also been described.<ref name="smo2" />

Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm<sub>2</sub>O<sub>3</sub> with samarium metal at high temperature (1000&nbsp;°C) and a pressure above 50&nbsp;kbar; lowering the pressure resulted in incomplete reaction. SmO has cubic rock-salt lattice structure.<ref name="smox" /><ref name="g1239">[[#Greenwood|Greenwood]], p. 1239</ref>

===Chalcogenides===
{{see also|Samarium monochalcogenides}}
Samarium forms a trivalent [[samarium(III) sulfide|sulfide]], [[selenide]] and [[telluride (chemistry)|telluride]]. Divalent chalcogenides SmS, SmSe and SmTe with a cubic rock-salt crystal structure are known. These chalcogenides convert from a semiconducting to metallic state at room temperature upon application of pressure.<ref>{{Cite journal |last1=Bakar |first1=Abu |last2=Afaq |first2=A. |last3=Khan |first3=M. Faizan |last4=ul Aarifeen |first4=Najm |last5=Imran Jamil |first5=M. |last6=Asif |first6=Muhammad |date=2020-01-01 |title=Insight into the structural, vibrational and thermodynamic properties of SmX (X = S, Se, Te) chalcogenides: First-principles investigations |url=https://www.sciencedirect.com/science/article/pii/S0921452619306209 |journal=Physica B: Condensed Matter |language=en |volume=576 |pages=411715 |doi=10.1016/j.physb.2019.411715 |s2cid=204206623 |issn=0921-4526|url-access=subscription }}</ref> Whereas the transition is continuous and occurs at about 20–30&nbsp;kbar in SmSe and SmTe, it is abrupt in SmS and requires only 6.5&nbsp;kbar. This effect results in a spectacular color change in SmS from black to golden yellow when its crystals of films are scratched or polished. The transition does not change the lattice symmetry, but there is a sharp decrease (~15%) in the crystal volume.<ref name="b1">{{Cite book |title=Magnetism: a synchrotron radiation approach |date=2006 |publisher=Springer |first1=E. |last1=Beaurepaire |isbn=978-3-540-33242-8 |location=Berlin |oclc=262692720}}</ref> It exhibits [[hysteresis]], i.e., when the pressure is released, SmS returns to the semiconducting state at a much lower pressure of about 0.4 kbar.<ref name="emsley" /><ref>{{cite journal|last1=Jayaraman|first1=A.|last2=Narayanamurti|first2=V.|last3=Bucher|first3=E.|last4=Maines|first4=R.|title=Continuous and Discontinuous Semiconductor-Metal Transition in Samarium Monochalcogenides Under Pressure|journal=Physical Review Letters|volume=25|page=1430|date=1970|doi=10.1103/PhysRevLett.25.1430|bibcode=1970PhRvL..25.1430J|issue=20}}</ref>

===Halides===

[[File:Samarium(III) chloride hexahydrate.jpg|thumb|right|Samarium trichloride]]

Samarium metal reacts with all the [[halogen]]s, forming trihalides:<ref name="g1236">[[#Greenwood|Greenwood]], pp. 1236, 1241</ref>
:2 Sm (s) + 3 X<sub>2</sub> (g) → 2 SmX<sub>3</sub> (s) (X = F, Cl, Br or I)

Their further reduction with samarium, lithium or sodium metals at elevated temperatures (about 700–900&nbsp;°C) yields the dihalides.<ref name="smcl2" /> The diiodide can also be prepared by heating SmI<sub>3</sub>, or by reacting the metal with [[1,2-Diiodoethane|1,2-diiodoethane]] in anhydrous [[tetrahydrofuran]] at room temperature:<ref name="g1240">[[#Greenwood|Greenwood]], p. 1240</ref>
:Sm (s) + ICH<sub>2</sub>-CH<sub>2</sub>I → SmI<sub>2</sub> + CH<sub>2</sub>=CH<sub>2</sub>.

In addition to dihalides, the reduction also produces many [[Non-stoichiometric compound|non-stoichiometric]] samarium halides with a well-defined crystal structure, such as Sm<sub>3</sub>F<sub>7</sub>, Sm<sub>14</sub>F<sub>33</sub>, Sm<sub>27</sub>F<sub>64</sub>,<ref name="smf2" /> Sm<sub>11</sub>Br<sub>24</sub>, Sm<sub>5</sub>Br<sub>11</sub> and Sm<sub>6</sub>Br<sub>13</sub>.<ref>{{cite journal |last1=Baernighausen |first1=H. |last2=Haschke |first2=John M. |title=Compositions and crystal structures of the intermediate phases in the samarium-bromine system |journal=Inorganic Chemistry |volume=17 |page=18 |date=1978 |doi=10.1021/ic50179a005}}</ref>

Samarium halides change their crystal structures when one type of halide anion is substituted for another, which is an uncommon behavior for most elements (e.g. actinides). Many halides have two major crystal phases for one composition, one being significantly more stable and another being metastable. The latter is formed upon compression or heating, followed by quenching to ambient conditions. For example, compressing the usual monoclinic samarium diiodide and releasing the pressure results in a PbCl<sub>2</sub>-type orthorhombic structure (density 5.90&nbsp;g/cm<sup>3</sup>),<ref>{{cite journal|last1=Beck|first1=H. P.|title=Hochdruckmodifikationen der Diiodide von Sr., Sm und Eu. Eine neue PbCl2-Variante?|journal=Zeitschrift für anorganische und allgemeine Chemie|volume=459|page=81|date=1979|doi=10.1002/zaac.19794590108}}</ref> and similar treatment results in a new phase of samarium triiodide (density 5.97&nbsp;g/cm<sup>3</sup>).<ref>{{cite journal|last1=Beck|first1=H. P.|last2=Gladrow|first2=E.|title=Zur Hochdruckpolymorphie der Seltenerd-Trihalogenide|journal=Zeitschrift für anorganische und allgemeine Chemie|volume=453|page=79|date=1979|doi=10.1002/zaac.19794530610}}</ref>

===Borides===
[[Sintering]] powders of samarium oxide and boron, in a vacuum, yields a powder containing several samarium boride phases; the ratio between these phases can be controlled through the mixing proportion.<ref name="smb6b" /> The powder can be converted into larger crystals of samarium borides using [[Electric arc furnace|arc melting]] or [[zone melting]] techniques, relying on the different melting/crystallization temperature of SmB<sub>6</sub> (2580&nbsp;°C), SmB<sub>4</sub> (about 2300&nbsp;°C) and SmB<sub>66</sub> (2150&nbsp;°C). All these materials are hard, brittle, dark-gray solids with the hardness increasing with the boron content.<ref name="smb6" /> Samarium diboride is too volatile to be produced with these methods and requires high pressure (about 65&nbsp;kbar) and low temperatures between 1140 and 1240&nbsp;°C to stabilize its growth. Increasing the temperature results in the preferential formation of SmB<sub>6</sub>.<ref name="smb2" />

====Samarium hexaboride====
{{Main|Samarium hexaboride}}

Samarium hexaboride is a typical intermediate-valence compound where samarium is present both as Sm<sup>2+</sup> and Sm<sup>3+</sup> ions in a 3:7 ratio.<ref name="smb6b">{{cite journal|last1=Nickerson|first1=J.|last2=White|first2=R.|last3=Lee|first3=K.|last4=Bachmann|first4=R.|last5=Geballe|first5=T.|last6=Hull|first6=G.|title=Physical Properties of SmB<sub>6</sub> |journal=Physical Review B|volume=3|page=2030|date=1971|doi=10.1103/PhysRevB.3.2030|issue=6|bibcode=1971PhRvB...3.2030N }}</ref> It belongs to a class of [[Kondo insulator]]s; at temperatures above 50&nbsp;K, its properties are typical of a Kondo metal, with metallic electrical conductivity characterized by strong electron scattering, whereas at lower temperatures, it behaves as a non-magnetic insulator with a narrow [[band gap]] of about 4–14&nbsp;[[electronvolt|meV]].<ref>{{cite journal |doi=10.1103/PhysRevB.52.R14308 |pmid=9980746 |last1=Nyhus |date=1995 |first1=P. |pages=14308–14311 |volume=52|last2=Cooper|journal=Physical Review B|first2=S.|last3=Fisk|first3=Z.|author4-link=John Sarrao |last4=Sarrao |first4=J. |title=Light scattering from gap excitations and bound states in SmB<sub>6</sub> |issue=20|bibcode=1995PhRvB..5214308N }}</ref> The cooling-induced metal-insulator transition in SmB<sub>6</sub> is accompanied by a sharp increase in the [[thermal conductivity]], peaking at about 15&nbsp;K. The reason for this increase is that electrons themselves do not contribute to the thermal conductivity at low temperatures, which is dominated by [[phonon]]s, but the decrease in electron concentration reduces the rate of electron-phonon scattering.<ref>{{cite journal |last1=Sera |first1=M. |last2=Kobayashi |first2=S. |last3=Hiroi |first3=M.|last4=Kobayashi|first4=N.|last5=Kunii|first5=S.|title=Thermal conductivity of RB<sub>6</sub> (R=Ce, Pr, Nd, Sm, Gd) single crystals |journal=Physical Review B |volume=54 |date=1996 |doi=10.1103/PhysRevB.54.R5207 |pmid=9986570|issue=8 |pages=R5207–R5210|bibcode=1996PhRvB..54.5207S }}</ref>

===Other inorganic compounds===
[[File:Samarium-sulfate.jpg|thumb|upright|alt=A tube of samarium sulfate|Samarium sulfate, Sm<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>]]
Samarium [[carbide]]s are prepared by melting a graphite-metal mixture in an inert atmosphere. After the synthesis, they are unstable in air and need to be studied under an inert atmosphere.<ref name="smc" /> Samarium monophosphide SmP is a [[semiconductor]] with a bandgap of 1.10&nbsp;eV, the same as in [[silicon]], and electrical conductivity of [[N-type semiconductor|n-type]]. It can be prepared by annealing at {{convert|1100|C|F}} an evacuated quartz ampoule containing mixed powders of phosphorus and samarium. Phosphorus is highly volatile at high temperatures and may explode, thus the heating rate has to be kept well below 1&nbsp;°C/min.<ref name="smp" /> A similar procedure is adopted for the monarsenide SmAs, but the synthesis temperature is higher at {{convert|1800|C|F}}.<ref name="smas" />

Numerous crystalline binary compounds are known for samarium and one of the group 14, 15, or 16 elements X, where X is Si, Ge, Sn, Pb, Sb or Te, and metallic alloys of samarium form another large group. They are all prepared by annealing mixed powders of the corresponding elements. Many of the resulting compounds are non-stoichiometric and have nominal compositions Sm<sub>a</sub>X<sub>b</sub>, where the b/a ratio varies between 0.5 and 3.<ref>{{cite journal |last1=Gladyshevskii|first1=E. I.|last2=Kripyakevich|first2=P. I.|title=Monosilicides of rare earth metals and their crystal structures|journal=Journal of Structural Chemistry|volume=5|page=789|date=1965|doi=10.1007/BF00744231|issue=6|bibcode=1965JStCh...5..789G |s2cid=93941853}}</ref><ref>{{cite journal|last1=Smith|first1=G. S.|last2=Tharp|first2=A. G.|last3=Johnson|first3=W.|title=Rare earth–germanium and –silicon compounds at 5:4 and 5:3 compositions|journal=Acta Crystallographica|volume=22|page=940|date=1967|doi=10.1107/S0365110X67001902|issue=6|doi-access=free|bibcode=1967AcCry..22..940S }}</ref>

===Organometallic compounds===
Samarium forms a [[Cyclopentadiene|cyclopentadienide]] {{chem2|Sm(C5H5)3}} and its chloroderivatives {{chem2|Sm(C5H5)2Cl}} and {{chem2|Sm(C5H5)Cl2}}. They are prepared by reacting samarium trichloride with {{chem2|NaC5H5}} in [[tetrahydrofuran]]. Contrary to cyclopentadienides of most other lanthanides, in {{chem2|Sm(C5H5)3}} some {{chem2|C5H5}} rings bridge each other by forming ring vertexes η<sup>1</sup> or edges η<sup>2</sup> toward another neighboring samarium, thus creating polymeric chains.<ref name="g1248" /> The chloroderivative {{chem2|Sm(C5H5)2Cl}} has a dimer structure, which is more accurately expressed as {{chem2|(η(5)\sC5H5)2Sm(\m\sCl)2(\h(5)\sC5H5)2}}. There, the chlorine bridges can be replaced, for instance, by iodine, hydrogen or nitrogen atoms or by [[cyanide|CN]] groups.<ref name="g1249">[[#Greenwood|Greenwood]], p. 1249</ref>

The ({{chem2|C5H5}})<sup>−</sup> ion in samarium cyclopentadienides can be replaced by the indenide ({{chem2|C9H7}})<sup>−</sup> or [[Cyclooctatetraene|cyclooctatetraenide]] ({{chem2|C8H8}})<sup>2−</sup> ring, resulting in {{chem2|Sm(C9H7)3}} or {{chem2|KSm(\h(8)\sC8H8)2}}. The latter compound has a structure similar to [[uranocene]]. There is also a cyclopentadienide of divalent samarium, {{chem2|Sm(C5H5)2}} a solid that sublimates at about {{convert|85|C|F}}. Contrary to [[ferrocene]], the {{chem2|C5H5}} rings in {{chem2|Sm(C5H5)2}} are not parallel but are tilted by 40°.<ref name="g1249" /><ref>{{cite journal|last1=Evans|first1=William J.|last2=Hughes|first2=Laura A.|last3=Hanusa|first3=Timothy P.|title=Synthesis and x-ray crystal structure of bis(pentamethylcyclopentadienyl) complexes of samarium and europium: (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>Sm and (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>Eu|journal=Organometallics|volume=5|page=1285|date=1986|doi=10.1021/om00138a001|issue=7}}</ref>

A [[Salt metathesis reaction|metathesis reaction]] in tetrahydrofuran or [[diethyl ether|ether]] gives [[alkyl]]s and [[aryl]]s of samarium:<ref name="g1249" />
:{{chem2|SmCl3 + 3LiR → SmR3 + 3LiCl}}
:{{chem2|Sm(OR)3 + 3LiCH(SiMe3)2 → Sm{CH(SiMe3)2}3 + 3LiOR}}

Here R is a hydrocarbon group and Me = [[methyl]].