Bis(trimethylsilyl)amine: Difference between revisions

|Verifiedfields = changed

|Watchedfields = changed

|verifiedrevid = 455209752

|ImageFileL1 = HMDS.png

|ImageNameL1 = Structural formula of bis(trimethylsilyl)amine

|ImageFileR1 = HMDS-3D.png

|ImageNameR1 = Spacefill model of bis(trimethylsilyl)amine

|PIN = 1,1,1-Trimethyl-''N''-(trimethylsilyl)silanamine<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = [[The Royal Society of Chemistry]] | date = 2014 | location = Cambridge | page = 135 | doi = 10.1039/9781849733069-FP001 | isbn = 978-0-85404-182-4}}</ref>

|OtherNames = Bis(trimethylsilyl)azane<br />Bis(trimethylsilyl)amine<br />1,1,1,3,3,3-Hexamethyldisilazane<br />

Hexamethyldisilazane

|Section1={{Chembox Identifiers

|Abbreviations = HMDS

|CASNo = 999-97-3

|CASNo_Ref = {{cascite|correct|CAS}}

|UNII_Ref = {{fdacite|correct|FDA}}

|UNII = H36C68P1BH

|PubChem = 13838

|PubChem1 = 18913873

|PubChem1_Comment = amine

|PubChem2 = 45051731

|PubChem2_Comment = sodium

|PubChem3 = 45051783

|PubChem3_Comment = potassium

|ChemSpiderID = 13238

|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

|ChEBI_Ref = {{ebicite|changed|EBI}}

|ChEBI = 85068

|EINECS = 213-668-5

|UNNumber = 2924, 3286

|MeSHName = Hexamethylsilazane

|RTECS = JM9230000

|SMILES = C[Si](C)(C)N[Si](C)(C)C

|SMILES1 = N([Si](C)(C)C)[Si](C)(C)C

|StdInChI_Ref = {{stdinchicite|correct|chemspider}}

|StdInChI = 1S/C6H19NSi2/c1-8(2,3)7-9(4,5)6/h7H,1-6H3

|InChI = 1/C6H19NSi2/c1-8(2,3)7-9(4,5)6/h7H,1-6H3

|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

|StdInChIKey = FFUAGWLWBBFQJT-UHFFFAOYSA-N

|InChIKey = FFUAGWLWBBFQJT-UHFFFAOYAF

|Beilstein = 635752}}

|Section2={{Chembox Properties

|C=6 | H=19 | N=1 | Si=2

|Appearance = Colorless liquid

|Density = 0.77 g cm⁻³

|MeltingPtC = -78

|BoilingPtC = 126

|Solubility = Slow hydrolysis

|RefractIndex = 1.4090

}}

|Section7={{Chembox Hazards

|NFPA-H = 3

|NFPA-F = 3

|NFPA-R = 1

|ExternalSDS = [https://www.alfa.com/en/msds/?language=EN&subformat=AGHS&sku=L16519 External MSDS]

}}

'''Bis(trimethylsilyl)amine''' (also known as '''hexamethyldisilazane''' and '''HMDS''') is an [[organosilicon compound]] with the [[molecular formula]] [(CH₃)₃Si]₂NH. The molecule is a derivative of [[ammonia]] with [[trimethylsilyl]] groups in place of two hydrogen atoms. An electron diffraction study shows that silicon-nitrogen bond length (173.5 pm) and Si-N-Si bond angle (125.5°) to be similar to disilazane (in which methyl groups are replaced by hydrogen atoms) suggesting that steric factors are not a factor in regulating angles in this case.<ref>{{cite book | author = D.A. Armitage | title = Organosilicon - an overview | chapter = 9.1 - Organosilanes |series= ''Comprehensive Organometallic Chemistry'' | year = 1982 | pages = 1–203 | doi = 10.1016/B978-008046518-0.00014-3 | isbn = 9780080465180 | chapter-url = https://www.sciencedirect.com/science/article/pii/B9780080465180000143}}</ref> This colorless liquid is a reagent and a precursor to bases that are popular in [[organic synthesis]] and [[organometallic chemistry]]. Additionally, HMDS is also increasingly used as molecular precursor in chemical vapor deposition techniques to deposit silicon carbonitride thin films or coatings.

==Synthesis and derivatives==

Bis(trimethylsilyl)amine is synthesized by treatment of [[trimethylsilyl chloride]] with [[ammonia]]:<ref>{{cite book | author = Robert C. Osthoff | author2 = Simon W. Kantor | title = Inorganic Syntheses | chapter = Organosilazane Compounds | series= [[Inorg. Synth.]] | year = 1957 | volume = 5 | pages = 55–64 | doi = 10.1002/9780470132364.ch16 | isbn = 978-0-470-13236-4}}</ref>

:2 (CH₃)₃SiCl + 3 NH₃ → [(CH₃)₃Si]₂NH + 2 NH₄Cl

[[Ammonium nitrate]] together with [[triethylamine]] can be used instead.<ref>{{cite journal | author = S.V. Chernyak | author2 = Yu. G. Yatluk | author3 = A.L. Suvorov |title = A Simple Synthesis of Hexamethyldisilazane (Translated from Zhurnal obshcheĭ khimiĭ, Vol. 70. No. 8, 2000. p1401)| journal = Russian Journal of General Chemistry | year = 2000 | volume = 70 | pages = 1313}}</ref> This method is also useful for ¹⁵N isotopic enrichment of HMDS.

:[[File:Synthesis of HMDS.tif|700 px]]

Alkali metal bis(trimethylsilyl)amides result from the [[deprotonation]] of bis(trimethylsilyl)amine. For example, [[lithium bis(trimethylsilyl)amide]] (LiHMDS) is prepared using [[n-Butyllithium|''n''-butyllithium]]:

:[(CH₃)₃Si]₂NH + BuLi → [(CH₃)₃Si]₂NLi + BuH

LiHMDS and other similar derivatives: [[sodium bis(trimethylsilyl)amide]] (NaHMDS) and [[potassium bis(trimethylsilyl)amide]] (KHMDS) are used as a non-nucleophilic bases in synthetic organic chemistry.

==Use as reagent==

Hexamethyldisilazane is employed as a reagent in many organic reactions:

1) HMDS is used as a [[reagent]] in [[condensation reaction]]s of [[heterocyclic compound]]s such as in the [[microwave chemistry|microwave synthesis]] of a [[Derivative (chemistry)|derivative]] of [[xanthine]]:<ref>{{cite journal |vauthors=Burbiel JC, Hockemeyer J, Müller CE |title=Microwave-assisted ring closure reactions: Synthesis of 8-substituted xanthine derivatives and related pyrimido- and diazepinopurinediones |journal=Beilstein J Org Chem |volume=2 |pages=20 |year=2006 |pmid=17067400 |doi=10.1186/1860-5397-2-20 |pmc=1698928 |doi-access=free }}</ref>

:[[File:HMDS application.png|400px|HMDS application]]

2) The HMDS mediated trimethylsilylation of alcohols, thiols, amines and amino acids as protective groups or for intermediary organosilicon compounds is found to be very efficient and replaced TMSCl reagent.<ref>{{cite journal | author = Benjamin A. Anderson | author2 = Vikas Sikervar | title = Hexamethyldisilazane|journal = [[Encyclopedia of Reagents for Organic Synthesis]] | doi = 10.1002/047084289X.rh016 | year = 2001 | isbn = 0471936235}}</ref>

Silylation of [[glutamic acid]] with excess hexamethyldisilazane and catalytic TMSCl in either refluxing [[xylene]] or [[acetonitrile]] followed by dilution with alcohol (methanol or ethanol) yields the derived lactam [[pyroglutamic acid]] in good yield.

:[[File:HMDS USES.svg|500 px]]

HMDS in the presence of catalytic iodine facilitates the silylation of alcohols in excellent yields.

:[[File:HMDS in silylation of alcohols.tif|500px]]

3) HMDS can be used to silylate laboratory glassware and make it hydrophobic, or automobile glass, just as [[Rain-X]] does.

4) In [[gas chromatography]], HMDS can be used to silylate OH groups of organic compounds to increase volatility, this way enabling GC-analysis of chemicals that are otherwise non-volatile.

In [[photolithography]], HMDS is often used as an adhesion promoter for [[photoresists]]. Best results are obtained by applying HMDS from the gas phase on heated substrates.<ref>{{cite web |url=http://www.cnf.cornell.edu/cnf_process_photo_resists.html#hmds |title=CNF - Photolithography Resist Processes and Capabilities |author=((Cornell NanoScale Science & Technology Facility)) |access-date=2008-01-29 |archive-date=2019-09-07 |archive-url=https://web.archive.org/web/20190907203828/http://www.cnf.cornell.edu/cnf_process_photo_resists.html#hmds |url-status=dead }}</ref><ref>{{cite web |title=YES Prime Oven {{!}} Stanford Nanofabrication Facility |url=https://snfexfab.stanford.edu/snf/operating-instructions/yes-prime-oven |website=snfexfab.stanford.edu |publisher=Stanford Nanofabrication Facility}}</ref>

In [[electron microscopy]], HMDS can be used as an alternative to [[critical point drying]] during sample preparation.<ref>{{cite journal |vauthors=Bray DF, Bagu J, Koegler P |title=Comparison of hexamethyldisilazane (HMDS), Peldri II, and critical-point drying methods for scanning electron microscopy of biological specimens |journal=Microsc. Res. Tech. |volume=26 |issue=6 |pages=489–95 |year=1993 |pmid=8305726 |doi=10.1002/jemt.1070260603|s2cid=26050695}}</ref>

In [[pyrolysis]]-gas chromatography-[[mass spectrometry]], HMDS is added to the analyte to create silylated diagnostic products during pyrolysis, in order to enhance detectability of compounds with polar functional groups.<ref>{{cite journal |author=Giuseppe Chiavari |author2=Daniele Fabbri |author3=Silvia Prati |name-list-style=amp |title=Gas chromatographic–mass spectrometric analysis of products arising from pyrolysis of amino acids in the presence of hexamethyldisilazane |journal=Journal of Chromatography A |volume=922 |issue=1–2 |pages=235–241 |year=2001 |doi=10.1016/S0021-9673(01)00936-0 |pmid=11486868}}</ref>

In [[plasma-enhanced chemical vapor deposition]] (PECVD), HMDS is used as a molecular precursor as a replacement to highly flammable and corrosive gasses like SiH₄, CH₄, NH₃ as it can be easily handled. HMDS is used in conjunction with a [[plasma (physics)|plasma]] of various gases such as argon, helium and nitrogen to deposit SiCN thin films/coatings with excellent mechanical, optical and electronic properties.<ref>{{cite journal | author = P. Jedrzejowski | author2 = J. Cizek | author3 = A. Amassian | author4 = J. E. Klemberg-Sapieha | author5 = J. Vlcek| author6 = L. Martinu | title = Mechanical and optical properties of hard SiCN coatings prepared by PECVD | journal = [[Thin Solid Films ]] | year = 2004 | volume = 447-448 | pages = 201–207 | doi = 10.1016/S0040-6090(03)01057-5| bibcode = 2004TSF...447..201J}}</ref>

[[Category:Trimethylsilyl compounds]]