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{{for|the monohydride|Beryllium monohydride}} |
{{for|the monohydride|Beryllium monohydride}} |
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{{chembox |
{{chembox |
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|Verifiedfields = changed |
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|verifiedrevid = 470456352 |
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|Name = Beryllium hydride |
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|ImageFile = Beryllium-hydride-3D-balls.png |
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|ImageSize = 230px |
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|Section1={{Chembox Identifiers |
|Section1={{Chembox Identifiers |
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|InChI = 1/Be.2H/rBeH2/h1H2 |
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|InChIKey = RWASOQSEFLDYLC-JICJMJRQAQ |
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|ChEBI_Ref = {{ebicite|correct|EBI}} |
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|ChEBI = 33787 |
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|SMILES = [BeH2] |
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|StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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|StdInChI = 1S/Be.2H |
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|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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|StdInChIKey = RWASOQSEFLDYLC-UHFFFAOYSA-N |
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|CASNo_Ref = {{cascite|correct|CAS}} |
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|CASNo = 7787-52-2 |
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|UNII_Ref = {{fdacite|correct|FDA}} |
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|UNII = 5M7P3TK96I |
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|Section2={{Chembox Properties |
|Section2={{Chembox Properties |
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|Formula = BeH{{sub|2}} |
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|MolarMass = 11.03 g mol{{sup|−1}} |
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|Appearance =white solid<ref name=G&E /> |
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|Density = 0.65 g/cm{{sup|3}} |
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|Solubility = decomposes |
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|SolubleOther = insoluble in [[diethyl ether]], [[toluene]] |
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|MeltingPtC = 250 |
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|MeltingPt_notes = decomposes |
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}} |
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|Section4={{Chembox Thermochemistry |
|Section4={{Chembox Thermochemistry |
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|HeatCapacity = 30.124 J/mol K |
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}} |
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|Section7={{Chembox Hazards |
|Section7={{Chembox Hazards |
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|REL = Ca C 0.0005 mg/m{{sup|3}} (as Be)<ref name=PGCH>{{PGCH|0054}}</ref> |
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|PEL = TWA 0.002 mg/m{{sup|3}}<br/>C 0.005 mg/m{{sup|3}} (30 minutes), with a maximum peak of 0.025 mg/m{{sup|3}} (as Be)<ref name=PGCH/> |
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|IDLH = Ca [4 mg/m{{sup|3}} (as Be)]<ref name=PGCH/> |
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}} |
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|Section8={{Chembox Related |
|Section8={{Chembox Related |
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|OtherCations = [[lithium hydride]], [[sodium hydride]], [[magnesium hydride]], [[calcium hydride]], [[borane|boron hydrides]], [[aluminium hydride]] |
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|OtherCompounds = [[beryllium fluoride]] |
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'''Beryllium hydride''' (systematically named '''beryllium dihydride''') is an [[inorganic compound]] with the [[chemical formula]] ({{Chem|BeH|2|}}) |
'''Beryllium hydride''' (systematically named '''poly[beryllane(2)]''' and '''beryllium dihydride''') is an [[inorganic compound]] with the [[chemical formula]] ({{Chem|BeH|2|}}){{sub|''n''}} (also written ({{Chem|[BeH|2|]}}){{sub|''n''}} or {{Chem|BeH|2}}). This [[alkaline earth hydride]] is a colourless solid that is insoluble in solvents that do not decompose it. Unlike the [[ionic bond|ionically bonded]] [[hydride]]s of the heavier [[alkaline earth metal|Group 2]] elements, beryllium hydride is [[covalent bond|covalently bonded]]<ref name=G&E>{{Greenwood&Earnshaw|p=115}}</ref> ([[three-center two-electron bond]]). |
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== Synthesis == |
== Synthesis == |
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Unlike the other [[alkaline earth metal|group 2]] metals, beryllium does not react with hydrogen.<ref name = "Wiberg&Holleman">Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier ISBN |
Unlike the other [[alkaline earth metal|group 2]] metals, beryllium does not react with hydrogen.<ref name = "Wiberg&Holleman">Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier {{ISBN|0-12-352651-5}}, p. 1048</ref> Instead, BeH{{sub|2}} is prepared from preformed beryllium(II) compounds. It was first synthesized in 1951 by treating [[dimethylberyllium]], Be(CH{{sub|3}}){{sub|2}}, with [[lithium aluminium hydride]], LiAlH{{sub|4}}.<ref>{{cite journal |author1=Glenn D. Barbaras |author2=Clyde Dillard |author3=A. E. Finholt |author4=Thomas Wartik |author5=K. E. Wilzbach |author6=H. I. Schlesinger |name-list-style=amp | year = 1951 | title = The Preparation of the Hydrides of Zinc, Cadmium, Beryllium, Magnesium and Lithium by the Use of Lithium Aluminum Hydride | journal = [[Journal of the American Chemical Society]] | volume = 73 | issue = 10 | pages = 4585–4590 | doi = 10.1021/ja01154a025 }}</ref> |
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Purer BeH |
Purer BeH{{sub|2}} forms from the [[pyrolysis]] of di-tert-butylberyllium, Be(C[CH{{sub|3}}]{{sub|3}}){{sub|2}} at 210°C.<ref>{{cite journal |author1=G. E. Coates |author2=F. Glockling |name-list-style=amp | year = 1954 | title = Di-tert.-butylberyllium and beryllium hydride | journal = [[Journal of the Chemical Society]] | pages = 2526–2529 | doi = 10.1039/JR9540002526}}</ref> |
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A route to highly pure samples |
A route to highly pure samples involves the reaction of [[triphenylphosphine]], PPh{{sub|3}}, with [[beryllium borohydride]], Be(BH{{sub|4}}){{sub|2}}:<ref name=G&E/> |
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:Be(BH |
:Be(BH{{sub|4}}){{sub|2}} + 2 PPh{{sub|3}} → BeH{{sub|2}} + 2 Ph{{sub|3}}PBH{{sub|3}} |
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== Structure == |
== Structure == |
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⚫ | BeH |
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=== Gaseous form === |
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⚫ | A more recent investigation found that crystalline beryllium hydride has a body-centred [[orthorhombic crystal system|orthorhombic]] [[unit cell]], containing a network of corner-sharing BeH |
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⚫ | |||
Isolated molecules of {{Chem|BeH|2}} (sometimes called dihydridoberyllium and written {{Chem|[BeH|2|]}} to emphasize the differences with the solid state) are only stable as a [[Concentration|dilute]] gas. When condensed, unsolvated {{Chem|BeH|2}} will spontaneously autopolymerise. |
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Free molecular BeH{{sub|2}} produced by high-temperature electrical discharge has been confirmed to have [[Linear molecular geometry|linear geometry]] with a Be-H bond length of 133.376 pm. Its hybridization is ''sp''.<ref>{{cite journal |author1=Peter F. Bernath |author2=Alireza Shayesteh |author3=Keith Tereszchuk |author4=Reginald Colin |year=2002 |title=The Vibration-Rotation Emission Spectrum of Free BeH<sub>2</sub> |journal=Science |volume=297 |issue=5585 |pages=1323–1324 |bibcode=2002Sci...297.1323B |doi=10.1126/science.1074580 |pmid=12193780 |s2cid=40961746}}</ref> |
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=== Condensed Beryllium hydride === |
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⚫ | BeH{{sub|2}} is usually formed as an amorphous white solid, but a [[hexagonal crystal system|hexagonal crystalline form]] with a higher density (~0.78 g/cm{{sup|3}}) was reported,<ref name="Brendel">{{cite journal |author1=G. J. Brendel |author2=E. M. Marlett |author3=L. M. Niebylski |name-list-style=amp | year = 1978 | title = Crystalline beryllium hydride | journal = [[Inorganic Chemistry (journal)|Inorganic Chemistry]] | volume = 17 | issue = 12 | pages = 3589–3592 | doi = 10.1021/ic50190a051}}</ref> prepared by heating amorphous BeH{{sub|2}} under pressure, with 0.5-2.5% [[lithium hydride|LiH]] as a catalyst. |
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[[File:BeH2 structure.svg|thumb|250px|Subunit of structure of BeH{{sub|2}}. Each Be is tetrahedral and each H is [[bridging ligand|doubly bridging]].<ref name="Smith" />|left]] |
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⚫ | A more recent investigation found that crystalline beryllium hydride has a body-centred [[orthorhombic crystal system|orthorhombic]] [[unit cell]], containing a network of corner-sharing BeH{{sub|4}} tetrahedra, in contrast to the flat, hydrogen-bridged, infinite chains previously thought to exist in crystalline BeH{{sub|2}}.<ref name=Smith>{{cite journal | author = Gordon S. Smith | author2 = Quintin C. Johnson | author3 = Deane K. Smith| author4 = D. E. Cox | author5 = Robert L. Snyder | author6 = Rong-Sheng Zhou | author7 = Allan Zalkin | name-list-style = amp | year = 1988 | title = The crystal and molecular structure of beryllium hydride | journal = [[Solid State Communications]] | volume = 67 | issue = 5 | pages = 491–494 | doi = 10.1016/0038-1098(84)90168-6 | bibcode = 1988SSCom..67..491S }}</ref> |
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Studies of the amorphous form also find that it consists of a network of corner shared tetrahedra.<ref>{{cite journal |author1=Sujatha Sampath |author2=Kristina M. Lantzky |author3=Chris J. Benmore |author4=Jörg Neuefeind |author5=Joan E. Siewenie |name-list-style=amp | year = 2003 | title = Structural quantum isotope effects in amorphous beryllium hydride | journal = J. Chem. Phys. | volume = 119 | issue = 23| pages = 12499 | doi = 10.1063/1.1626638|bibcode=2003JChPh.11912499S }}</ref> |
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== Chemical properties == |
== Chemical properties == |
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Beryllium hydride reacts slowly with water but is rapidly hydrolysed by acid such as [[hydrogen chloride]] to form [[beryllium chloride]].<ref name = "Wiberg&Holleman"/> |
Beryllium hydride reacts slowly with water but is rapidly hydrolysed by acid such as [[hydrogen chloride]] to form [[beryllium chloride]].<ref name = "Wiberg&Holleman"/> |
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:BeH{{sub|2}} + 2 H{{sub|2}}O → Be(OH){{sub|2}} + 2 H{{sub|2}} |
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===Reaction with Lewis bases=== |
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⚫ | Beryllium hydride reacts with [[trimethylamine]], N(CH |
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:BeH{{sub|2}} + 2 HCl → BeCl{{sub|2}} + 2 H{{sub|2}} |
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== Dihydridoberyllium == |
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Dihydridoberyllium is a related compound with the chemical formula {{Chem|BeH|2}} (also written {{Chem|[BeH|2|]}}). It is a gas that cannot persist undiluted. Unsolvated dihydridoberyllium will spontaneously autopolymerise to oligomers. Free molecular BeH<sub>2</sub> produced by electrical discharge at high temperature has been confirmed as linear with a Be-H bond length of 133.376 pm. Its hybridisation is sp. |
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<ref>{{cite journal |author1=Peter F. Bernath |author2=Alireza Shayesteh |author3=Keith Tereszchuk |author4=Reginald Colin | year = 2002 | title = The Vibration-Rotation Emission Spectrum of Free BeH<sub>2</sub> | journal = Science | volume = 297 | issue = 5585| pages = 1323–1324 | doi = 10.1126/science.1074580 | pmid = 12193780 }}</ref> |
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===Reaction with Lewis bases=== |
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The two-coordinate hydridoberyllium group can accept an electron-pair donating [[ligand]] (L) into the molecule by adduction:<ref name="Sharp2000">{{Cite journal |last1=Sharp |first1=Stephanie B. |last2=Gellene |first2=Gregory I. |date=23 November 2000 |title=σ Bond Activation by Cooperative Interaction with ''n''s{{sup|2}} Atoms: Be + ''n'' {{Chem|H|2}}, ''n'' = 1−3 |journal=The Journal of Physical Chemistry A |volume=104 |issue=46 |pages=10951–10957 |doi=10.1021/jp002313m}}</ref> |
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:{{Chem|[BeH|2|]}} + L → {{Chem|[BeH|2|L]}} |
:{{Chem|[BeH|2|]}} + L → {{Chem|[BeH|2|L]}} |
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Because |
Because these reactions are energetically favored, beryllium hydride has [[lewis acids and bases|Lewis-acidic]] character. |
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⚫ | Beryllium hydride reacts with [[trimethylamine]], N(CH{{sub|3}}){{sub|3}} to form a dimeric adduct with bridging hydrides.<ref name="Shepherd1969">{{Cite journal|last=Shepherd Jr.|first=Lawrence H. |author2=Ter Haar, G. L. |author3=Marlett, Everett M.|title=Amine complexes of beryllium hydride|journal=Inorganic Chemistry|date=April 1969|volume=8|issue=4|pages=976–979|doi=10.1021/ic50074a051}}</ref> However, with [[dimethylamine]], HN(CH{{sub|3}}){{sub|2}} it forms a trimeric beryllium diamide, [Be(N(CH{{sub|3}}){{sub|2}}){{sub|2}}]{{sub|3}}, and hydrogen.<ref name="Wiberg&Holleman" /> |
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== References == |
== References == |
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{{Hydrides by group}} |
{{Hydrides by group}} |
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{{DEFAULTSORT:beryllium hydride}} |
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[[Category:Beryllium compounds]] |
[[Category:Beryllium compounds]] |
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[[Category:Metal hydrides]] |
[[Category:Metal hydrides]] |
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[[Category:Substances discovered in the 1950s]] |
Latest revision as of 18:43, 6 April 2024
Names | |
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Other names
Beryllium dihydride
Beryllium hydride Beryllane | |
Identifiers | |
3D model (JSmol)
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ChEBI | |
ChemSpider | |
PubChem CID
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
BeH2 | |
Molar mass | 11.03 g mol−1 |
Appearance | white solid[1] |
Density | 0.65 g/cm3 |
Melting point | 250 °C (482 °F; 523 K) decomposes |
decomposes | |
Solubility | insoluble in diethyl ether, toluene |
Thermochemistry | |
Heat capacity (C)
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30.124 J/mol K |
Hazards | |
NIOSH (US health exposure limits): | |
PEL (Permissible)
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TWA 0.002 mg/m3 C 0.005 mg/m3 (30 minutes), with a maximum peak of 0.025 mg/m3 (as Be)[2] |
REL (Recommended)
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Ca C 0.0005 mg/m3 (as Be)[2] |
IDLH (Immediate danger)
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Ca [4 mg/m3 (as Be)][2] |
Related compounds | |
Other cations
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lithium hydride, sodium hydride, magnesium hydride, calcium hydride, boron hydrides, aluminium hydride |
Related compounds
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beryllium fluoride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Beryllium hydride (systematically named poly[beryllane(2)] and beryllium dihydride) is an inorganic compound with the chemical formula (BeH
2)n (also written ([BeH
2])n or BeH
2). This alkaline earth hydride is a colourless solid that is insoluble in solvents that do not decompose it. Unlike the ionically bonded hydrides of the heavier Group 2 elements, beryllium hydride is covalently bonded[1] (three-center two-electron bond).
Synthesis[edit]
Unlike the other group 2 metals, beryllium does not react with hydrogen.[3] Instead, BeH2 is prepared from preformed beryllium(II) compounds. It was first synthesized in 1951 by treating dimethylberyllium, Be(CH3)2, with lithium aluminium hydride, LiAlH4.[4]
Purer BeH2 forms from the pyrolysis of di-tert-butylberyllium, Be(C[CH3]3)2 at 210°C.[5]
A route to highly pure samples involves the reaction of triphenylphosphine, PPh3, with beryllium borohydride, Be(BH4)2:[1]
- Be(BH4)2 + 2 PPh3 → BeH2 + 2 Ph3PBH3
Structure[edit]
Gaseous form[edit]
Isolated molecules of BeH
2 (sometimes called dihydridoberyllium and written [BeH
2] to emphasize the differences with the solid state) are only stable as a dilute gas. When condensed, unsolvated BeH
2 will spontaneously autopolymerise.
Free molecular BeH2 produced by high-temperature electrical discharge has been confirmed to have linear geometry with a Be-H bond length of 133.376 pm. Its hybridization is sp.[6]
Condensed Beryllium hydride[edit]
BeH2 is usually formed as an amorphous white solid, but a hexagonal crystalline form with a higher density (~0.78 g/cm3) was reported,[7] prepared by heating amorphous BeH2 under pressure, with 0.5-2.5% LiH as a catalyst.
A more recent investigation found that crystalline beryllium hydride has a body-centred orthorhombic unit cell, containing a network of corner-sharing BeH4 tetrahedra, in contrast to the flat, hydrogen-bridged, infinite chains previously thought to exist in crystalline BeH2.[8]
Studies of the amorphous form also find that it consists of a network of corner shared tetrahedra.[9]
Chemical properties[edit]
Reaction with water and acids[edit]
Beryllium hydride reacts slowly with water but is rapidly hydrolysed by acid such as hydrogen chloride to form beryllium chloride.[3]
- BeH2 + 2 H2O → Be(OH)2 + 2 H2
- BeH2 + 2 HCl → BeCl2 + 2 H2
Reaction with Lewis bases[edit]
The two-coordinate hydridoberyllium group can accept an electron-pair donating ligand (L) into the molecule by adduction:[10]
- [BeH
2] + L → [BeH
2L]
Because these reactions are energetically favored, beryllium hydride has Lewis-acidic character.
The reaction with lithium hydride (in which the hydride ion is the Lewis base), forms sequentially LiBeH3 and Li2BeH4.[3] The latter contains the tetrahydridoberyllate(2-) anion BeH2−
4.
Beryllium hydride reacts with trimethylamine, N(CH3)3 to form a dimeric adduct with bridging hydrides.[11] However, with dimethylamine, HN(CH3)2 it forms a trimeric beryllium diamide, [Be(N(CH3)2)2]3, and hydrogen.[3]
References[edit]
- ^ a b c Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 115. ISBN 978-0-08-037941-8.
- ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0054". National Institute for Occupational Safety and Health (NIOSH).
- ^ a b c d Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5, p. 1048
- ^ Glenn D. Barbaras; Clyde Dillard; A. E. Finholt; Thomas Wartik; K. E. Wilzbach & H. I. Schlesinger (1951). "The Preparation of the Hydrides of Zinc, Cadmium, Beryllium, Magnesium and Lithium by the Use of Lithium Aluminum Hydride". Journal of the American Chemical Society. 73 (10): 4585–4590. doi:10.1021/ja01154a025.
- ^ G. E. Coates & F. Glockling (1954). "Di-tert.-butylberyllium and beryllium hydride". Journal of the Chemical Society: 2526–2529. doi:10.1039/JR9540002526.
- ^ Peter F. Bernath; Alireza Shayesteh; Keith Tereszchuk; Reginald Colin (2002). "The Vibration-Rotation Emission Spectrum of Free BeH2". Science. 297 (5585): 1323–1324. Bibcode:2002Sci...297.1323B. doi:10.1126/science.1074580. PMID 12193780. S2CID 40961746.
- ^ G. J. Brendel; E. M. Marlett & L. M. Niebylski (1978). "Crystalline beryllium hydride". Inorganic Chemistry. 17 (12): 3589–3592. doi:10.1021/ic50190a051.
- ^ a b Gordon S. Smith; Quintin C. Johnson; Deane K. Smith; D. E. Cox; Robert L. Snyder; Rong-Sheng Zhou & Allan Zalkin (1988). "The crystal and molecular structure of beryllium hydride". Solid State Communications. 67 (5): 491–494. Bibcode:1988SSCom..67..491S. doi:10.1016/0038-1098(84)90168-6.
- ^ Sujatha Sampath; Kristina M. Lantzky; Chris J. Benmore; Jörg Neuefeind & Joan E. Siewenie (2003). "Structural quantum isotope effects in amorphous beryllium hydride". J. Chem. Phys. 119 (23): 12499. Bibcode:2003JChPh.11912499S. doi:10.1063/1.1626638.
- ^ Sharp, Stephanie B.; Gellene, Gregory I. (23 November 2000). "σ Bond Activation by Cooperative Interaction with ns2 Atoms: Be + n H
2, n = 1−3". The Journal of Physical Chemistry A. 104 (46): 10951–10957. doi:10.1021/jp002313m. - ^ Shepherd Jr., Lawrence H.; Ter Haar, G. L.; Marlett, Everett M. (April 1969). "Amine complexes of beryllium hydride". Inorganic Chemistry. 8 (4): 976–979. doi:10.1021/ic50074a051.