Bis(trimethylsilyl)amine

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Bis(trimethylsilyl)amine
Structural formula of bis(trimethylsilyl)amine HMDS.png
Structural formula of bis(trimethylsilyl)amine
Spacefill model of bis(trimethylsilyl)amine HMDS-3D.png
Spacefill model of bis(trimethylsilyl)amine
Names
Preferred IUPAC name
1,1,1-Trimethyl-N-(trimethylsilyl)silanamine [1]
Other names
Bis(trimethylsilyl)azane
Bis(trimethylsilyl)amine
1,1,1,3,3,3-Hexamethyldisilazane
Hexamethyldisilazane
Identifiers
3D model (JSmol)
AbbreviationsHMDS
635752
ChEBI
ChemSpider
ECHA InfoCard 100.012.425 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 213-668-5
MeSH Hexamethylsilazane
PubChem CID
RTECS number
  • JM9230000
UNII
UN number 2924, 3286
  • InChI=1S/C6H19NSi2/c1-8(2,3)7-9(4,5)6/h7H,1-6H3 Yes check.svgY
    Key: FFUAGWLWBBFQJT-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C6H19NSi2/c1-8(2,3)7-9(4,5)6/h7H,1-6H3
    Key: FFUAGWLWBBFQJT-UHFFFAOYAF
  • C[Si](C)(C)N[Si](C)(C)C
  • N([Si](C)(C)C)[Si](C)(C)C
Properties
C6H19NSi2
Molar mass 161.395 g·mol−1
AppearanceColorless liquid
Density 0.77 g cm−3
Melting point −78 °C (−108 °F; 195 K)
Boiling point 126 °C (259 °F; 399 K)
Slow hydrolysis
1.4090
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
3
3
1
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

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. [2] 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.

Contents

Synthesis and derivatives

Bis(trimethylsilyl)amine is synthesized by treatment of trimethylsilyl chloride with ammonia: [3]

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

Ammonium nitrate together with triethylamine can be used instead. [4] This method is also useful for 15N isotopic enrichment of HMDS.

Synthesis of HMDS.tif

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:

[(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 reactions of heterocyclic compounds such as in the microwave synthesis of a derivative of xanthine: [5]

HMDS application.png

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. [6]

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.

HMDS USES.svg

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

HMDS in silylation of alcohols.tif

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.

Other uses

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. [7] [8]

In electron microscopy, HMDS can be used as an alternative to critical point drying during sample preparation. [9]

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. [10]

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 of various gases such as argon, helium and nitrogen to deposit SiCN thin films/coatings with excellent mechanical, optical and electronic properties. [11]

See also

Related Research Articles

<span class="mw-page-title-main">Trimethylsilyl group</span> Functional group

A trimethylsilyl group (abbreviated TMS) is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom [−Si(CH3)3], which is in turn bonded to the rest of a molecule. This structural group is characterized by chemical inertness and a large molecular volume, which makes it useful in a number of applications.

In inorganic chemistry, chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. Each such chemical has at least one silicon-chlorine bond. Trichlorosilane is produced on the largest scale. The parent chlorosilane is silicon tetrachloride.

<span class="mw-page-title-main">Sodium bis(trimethylsilyl)amide</span> Chemical compound

Sodium bis(trimethylsilyl)amide is the organosilicon compound with the formula NaN(Si 3)2. This species, usually called NaHMDS, is a strong base used for deprotonation reactions or base-catalyzed reactions. Its advantages are that it is commercially available as a solid and it is soluble not only in ethers, such as THF or diethyl ether, but also in aromatic solvents, like benzene and toluene by virtue of the lipophilic TMS groups.

<span class="mw-page-title-main">Trimethylsilyldiazomethane</span> Chemical compound

Trimethylsilyldiazomethane is the organosilicon compound with the formula (CH3)3SiCHN2. It is classified as a diazo compound. Trimethylsilyldiazomethane is a commercially available reagent used in organic chemistry as a methylating agent and as a source of CH2 group. Its behavior is akin to the less convenient reagent diazomethane.

<span class="mw-page-title-main">Trimethylsilyl chloride</span> Organosilicon compound with the formula (CH3)3SiCl

Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound, with the formula (CH3)3SiCl, often abbreviated Me3SiCl or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. It is widely used in organic chemistry.

<span class="mw-page-title-main">Organosilicon chemistry</span> Organometallic compound containing carbon–silicon bonds

Organosilicon chemistry is the study of organometallic compounds containing carbon–silicon bonds, to which they are called organosilicon compounds. Most organosilicon compounds are similar to the ordinary organic compounds, being colourless, flammable, hydrophobic, and stable to air. Silicon carbide is an inorganic compound.

<span class="mw-page-title-main">Trimethylsilyl cyanide</span> Chemical compound

Trimethylsilyl cyanide is the chemical compound with the formula (CH3)3SiCN. This volatile liquid consists of a cyanide group, that is CN, attached to a trimethylsilyl group. The molecule is used in organic synthesis as the equivalent of hydrogen cyanide. It is prepared by the reaction of lithium cyanide and trimethylsilyl chloride:

<span class="mw-page-title-main">Hexamethyldisilane</span> Chemical compound

Hexamethyldisilane (TMS2) is the organosilicon compound with the formula Si2(CH3)6, abbreviated Si2Me6. It is a colourless liquid, soluble in organic solvents.

<span class="mw-page-title-main">Hexamethyldisiloxane</span> Chemical compound

Hexamethyldisiloxane (HMDSO or MM) is an organosilicon compound with the formula O[Si(CH3)3]2. This volatile colourless liquid is used as a solvent and as a reagent in organic synthesis. It is prepared by the hydrolysis of trimethylsilyl chloride. The molecule is the protypical disiloxane and resembles a subunit of polydimethylsiloxane.

HMDS may refer to:

<span class="mw-page-title-main">Trimethylsilyl azide</span> Chemical compound

Trimethylsilyl azide is the organosilicon compound with the formula (CH3)3SiN3. A colorless liquid, it is a reagent in organic chemistry, serving as the equivalent of hydrazoic acid.

<span class="mw-page-title-main">Lithium bis(trimethylsilyl)amide</span> Chemical compound

Lithium bis(trimethylsilyl)amide is a lithiated organosilicon compound with the formula LiN(Si(CH3)3)2. It is commonly abbreviated as LiHMDS or Li(HMDS) (lithium hexamethyldisilazide - a reference to its conjugate acid HMDS) and is primarily used as a strong non-nucleophilic base and as a ligand. Like many lithium reagents, it has a tendency to aggregate and will form a cyclic trimer in the absence of coordinating species.

<span class="mw-page-title-main">Trimethylsilyl trifluoromethanesulfonate</span> Chemical compound

Trimethylsilyl trifluoromethanesulfonate (TMSOTf) is an organosilicon compound with the formula (CH3)3SiO3SCF3. It is a colorless moisture-sensitive liquid. It is the trifluoromethanesulfonate derivative of trimethylsilyl. It is mainly used to activate ketones and aldehydes in organic synthesis.

<span class="mw-page-title-main">Bis(trimethylsilyl)acetamide</span> Chemical compound

Bis(trimethylsilyl)acetamide (BSA) is an organosilicon compound with the formula MeC(OSiMe3)NSiMe3 (Me = CH3). It is a colorless liquid that is soluble in diverse organic solvents, but reacts rapidly with moisture and solvents containing OH and NH groups. It is used in analytical chemistry to increase the volatility of analytes, e.g., for gas chromatography. It is also used to introduce the trimethylsilyl protecting group in organic synthesis. A related reagent is N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA).

Silylation is the introduction of one or more (usually) substituted silyl groups (R3Si) to a molecule. Silylations are core methods for production of organosilicon chemistry. Silanization involves similar methods but usually refers to attachment of silyl groups to solids.

<span class="mw-page-title-main">BSTFA</span> Chemical compound

N,O-Bis(trimethylsilyl)trifluoroacetamide (BSTFA) is an organosilicon compound. It is a colorless liquid that is very sensitive to traces of water or alcohols.

<span class="mw-page-title-main">Metal bis(trimethylsilyl)amides</span>

Metal bis(trimethylsilyl)amides are coordination complexes composed of a cationic metal M with anionic bis(trimethylsilyl)amide ligands (the −N 2 monovalent anion, or −N 2 monovalent group, and are part of a broader category of metal amides.

<span class="mw-page-title-main">Trimethylsilyl iodide</span> Chemical compound

Trimethylsilyl iodide (iodotrimethylsilane or TMSI) is an organosilicon compound with the chemical formula (CH3)3SiI. It is a colorless, volatile liquid at room temperature.

<span class="mw-page-title-main">Tris(trimethylsilyl)amine</span> Chemical compound

Tris(trimethylsilyl)amine is the simplest tris(trialkylsilyl)amine which are having the general formula (R3Si)3N, in which all three hydrogen atoms of the ammonia are replaced by trimethylsilyl groups (-Si(CH3)3). Tris(trimethylsilyl)amine has been for years in the center of scientific interest as a stable intermediate in chemical nitrogen fixation (i. e. the conversion of atmospheric nitrogen N2 into organic substrates under normal conditions).

<span class="mw-page-title-main">(Trimethylsilyl)methyllithium</span> Chemical compound

(Trimethylsilyl)methyllithium is classified both as an organolithium compound and an organosilicon compound. It has the empirical formula LiCH2Si(CH3)3, often abbreviated LiCH2tms. It crystallizes as the hexagonal prismatic hexamer [LiCH2tms]6, akin to some polymorphs of methyllithium. Many adducts have been characterized including the diethyl ether complexed cubane [Li4(μ3-CH2tms)4(Et2O)2] and [Li2(μ-CH2tms)2(tmeda)2].

References

  1. ↑ Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 135. doi:10.1039/9781849733069-FP001. ISBN   978-0-85404-182-4.
  2. ↑ D.A. Armitage (1982). "9.1 - Organosilanes". Organosilicon - an overview. Comprehensive Organometallic Chemistry. pp. 1–203. doi:10.1016/B978-008046518-0.00014-3. ISBN   9780080465180.
  3. ↑ Robert C. Osthoff; Simon W. Kantor (1957). "Organosilazane Compounds". Inorganic Syntheses. Inorg. Synth. Vol. 5. pp. 55–64. doi:10.1002/9780470132364.ch16. ISBN   978-0-470-13236-4.
  4. ↑ S.V. Chernyak; Yu. G. Yatluk; A.L. Suvorov (2000). "A Simple Synthesis of Hexamethyldisilazane (Translated from Zhurnal obshcheĭ khimiĭ, Vol. 70. No. 8, 2000. p1401)". Russian Journal of General Chemistry. 70: 1313.
  5. ↑ Burbiel JC, Hockemeyer J, Müller CE (2006). "Microwave-assisted ring closure reactions: Synthesis of 8-substituted xanthine derivatives and related pyrimido- and diazepinopurinediones". Beilstein J Org Chem. 2: 20. doi: 10.1186/1860-5397-2-20 . PMC   1698928 . PMID   17067400.
  6. ↑ Benjamin A. Anderson; Vikas Sikervar (2001). "Hexamethyldisilazane". Encyclopedia of Reagents for Organic Synthesis . doi:10.1002/047084289X.rh016. ISBN   0471936235.
  7. ↑ Cornell NanoScale Science & Technology Facility. "CNF - Photolithography Resist Processes and Capabilities". Archived from the original on 2019-09-07. Retrieved 2008-01-29.
  8. ↑ "YES Prime Oven | Stanford Nanofabrication Facility". snfexfab.stanford.edu. Stanford Nanofabrication Facility.
  9. ↑ Bray DF, Bagu J, Koegler P (1993). "Comparison of hexamethyldisilazane (HMDS), Peldri II, and critical-point drying methods for scanning electron microscopy of biological specimens". Microsc. Res. Tech. 26 (6): 489–95. doi:10.1002/jemt.1070260603. PMID   8305726. S2CID   26050695.
  10. ↑ Giuseppe Chiavari; Daniele Fabbri & Silvia Prati (2001). "Gas chromatographic–mass spectrometric analysis of products arising from pyrolysis of amino acids in the presence of hexamethyldisilazane". Journal of Chromatography A. 922 (1–2): 235–241. doi:10.1016/S0021-9673(01)00936-0. PMID   11486868.
  11. ↑ P. Jedrzejowski; J. Cizek; A. Amassian; J. E. Klemberg-Sapieha; J. Vlcek; L. Martinu (2004). "Mechanical and optical properties of hard SiCN coatings prepared by PECVD". Thin Solid Films . 447–448: 201–207. Bibcode:2004TSF...447..201J. doi:10.1016/S0040-6090(03)01057-5.
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