'''Tetraborane''' (systematically named '''''arachno''-tetraborane(10)''') was the first [[Boranes|boron]][[hydride]] compound to be discovered.<ref>{{Cite journal |last=Wiberg |first=E. |date=1977-01-01 |title=Alfred Stock and the renaissance of inorganic chemistry |url=https://www.degruyter.com/document/doi/10.1351/pac197749060691/html |journal=Pure and Applied Chemistry |language=en |volume=49 |issue=6 |pages=691–700 |doi=10.1351/pac197749060691 |issn=1365-3075}}</ref> It was classified by [[Alfred Stock]] and MessenezCarl Massenez in 1912 and was first isolated by AlfredStock.<ref>{{Cite journal |last=Stock |first=Alfred |last2=Massenez |first2=Carl |date=1912-10-01 |title=Borwasserstoffe |url=https://onlinelibrary.wiley.com/doi/10.1002/cber.191204503113 |journal=Berichte der deutschen chemischen Gesellschaft |language=en |volume=45 |issue=3 |pages=3539–3568 |doi=10.1002/cber.191204503113 |issn=0365-9496}}</ref> It has a relatively low boiling point at 18 °C and is a gas at room temperature. Tetraborane gas is foul smelling and toxic.
==History==
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==Preparation==
Tetraborane can be produced via a reaction between acid and magnesium or beryllium [[Boride|borides]], with smaller quantities from aluminum, ormanganese, berylliumand cerium borides.<ref>{{Cite book |last=Stock |first=Alfred |url=https://archive.org/details/hydridesofborons0000alfr/ |title=Hydrides of Boron and Silicon |publisher=[[Cornell University Press]] |year=1933 |pages=60}}</ref> [[Hydrolysis]] of magnesium boride, [[hydrogenation]] of boron halides at high temperatures and the [[pyrolysis]] of [[diborane]] also produce tetraborane. The hydrolysis of magnesium boride was one of the first reactions to give a high yield (14%) of tetraborane.{{Citation needed|date=July 2023}} [[Phosphoric acid]] proved to be the most efficient acid (othercompared thanto [[Hydrochloric acid|hydrochloric]] and [[sulfuric acid]]) in the reaction with magnesium boride.<ref>{{Cite book |last=Stock |first=Alfred |url=https://archive.org/details/hydridesofborons0000alfr/ |title=Hydrides of Boron and Silicon |publisher=[[Cornell University Press]] |year=1933 |pages=41}}</ref>▼
{{Unreferenced section|date=August 2020}}
▲Tetraborane can be produced via a reaction between acid and magnesium, aluminum, or beryllium borides. Hydrolysis of magnesium boride, [[hydrogenation]] of boron halides at high temperatures and the pyrolysis of [[diborane]] also produce tetraborane. The hydrolysis of magnesium boride was one of the first reactions to give a high yield (14%) of tetraborane. Phosphoric acid proved to be the most efficient acid (other than hydrochloric and sulfuric acid) in the reaction with magnesium boride.
==Isomers==
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:Path 1: Dissociative pathway via B<sub>3</sub>H<sub>7</sub> and BH<sub>3</sub>
:Path 2: Concerted pathway over two transition states separated by a local minimum
:Path 3: Another concerted pathway involving penta-coordinated isomers as intermediates
Paths 2 and 3 are more likely, because they are more energetically favored with energies of 33.1 kcal/mol and 22.7 kcal/mol respectively.<ref>{{Cite journal|last1=Ramakrishna|first1=Vinutha|last2=Duke|first2=Brian J.|date=2004|title=Can the Bis(diboranyl) Structure of B4H10 Be Observed? The Story Continues|url=https://pubs.acs.org/doi/10.1021/ic049558o|journal=Inorganic Chemistry|language=en|volume=43|issue=25|pages=8176–8184|doi=10.1021/ic049558o|pmid=15578859|issn=0020-1669}}</ref>
==Safety==
Because it is easily oxidized it must be kept under vacuum. Tetraborane ignites when it comes in contact with air, oxygen, and nitric acid. [[Boranes]] in general including tetraborane have been deemed very toxic and are biologically destructive. A study consisting of small daily exposure of the chemical to rabbits and rats resulted in fatality.<ref>{{cite web |url=http://voh.chem.ucla.edu/vohtar/spring05/classes/172/pdf/p21-30Borane.pdf |title=Archived copy |access-date=2011-05-11 |url-status=dead |archive-url=https://web.archive.org/web/20110727012047/http://voh.chem.ucla.edu/vohtar/spring05/classes/172/pdf/p21-30Borane.pdf |archive-date=2011-07-27 }}</ref>
