Hexamethylcyclotrisilazane is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

or . Its

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...

consists of a six-member ring of three

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...

atoms alternating with three

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

atoms, with two

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...

s bonded to each silicon and one

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

atom bonded to each nitrogen. It can be described as a derivative of the hypothetical compound cyclotrisilazane , or as a

cyclic Cycle, cycles, or cyclic may refer to: Anthropology and social sciences * Cyclic history, a theory of history * Cyclical theory, a theory of American political history associated with Arthur Schlesinger, Sr. * Social cycle, various cycles in soc ...

trimer of hypothetical dimethylsilazane . The compound is a clear colorless liquid at room temperature. The compound has been extensively studied because of its applications in the

semiconductor A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...

industry, as a precursor for the deposition of fils of

silicon nitride Silicon nitride is a chemical compound of the elements silicon and nitrogen. is the most thermodynamically stable and commercially important of the silicon nitrides, and the term "silicon nitride" commonly refers to this specific composition. It ...

and silicon carbonitride and as an additive in

photoresist A photoresist (also known simply as a resist) is a light-sensitive material used in several processes, such as photolithography and photoengraving, to form a patterned coating on a surface. This process is crucial in the electronic industry. T ...

formulations. It has also been proposed as an additive to

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

for

liquid chromatography In chemical analysis, chromatography is a laboratory technique for the Separation process, separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it ...

. Other names for the compound are 2,2,4,4,6,6-hexamethyl-1,3,5,2,4,6-triazatrisilinane (

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

), 1,1,3,3,5,5-hexamethyl-2,4,6,1,3,5-triazatrisilinane, and 2,4,4,6,6-hexamethyl-1,3,5-triaza-2,4,6-trisilacyclohexane. The name is often abbreviated HMCTS or HMCTSZN.

Structure

The silicon-nitrogen ring is nearly planar. The interatomic distances are: Si-N = 1.728 Å, Si-C = 1.871 Å, C-H = 1.124 Å. The approximate bond angles are N-Si-N ≈ 108°, Si-N-Si ≈ 127°, C-Si-C ≈ 109°, H-C-H ≈ 112°.

Synthesis

The compound was obtained in 1948 by Brewer and Haber by introducing

dimethyldichlorosilane Dimethyldichlorosilane is a tetrahedral, organosilicon compound with the formula Si(CH3)2Cl2. At room temperature it is a colorless liquid that readily reacts with water to form both linear and cyclic Si-O chains. Dimethyldichlorosilane is made ...

into liquid

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

, and then extracting the precipitate with

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

. The reaction yields a mixture of compounds, chiefly the trimer and the

tetramer A tetramer () (''tetra-'', "four" + '' -mer'', "parts") is an oligomer formed from four monomers or subunits. The associated property is called ''tetramery''. An example from inorganic chemistry is titanium methoxide with the empirical formula Ti ...

octamethyltetrasilazane. The trimer can be separated from the other products by fractional distillation. The yield can be improved by converting the tetramer, through reaction with hydrogen in the presence of suitable catalysts.

References

Stuart D. Brewer and Charles P. Haber (1948): "Alkylsilazanes and Some Related Compounds". ''Journal of the American Chemical Society'', volume 70, issue 11, pages 3888-3891. FAR Chemical (2020):
Product 654201: Hexamethylcyclotrisilazane
. Catalog page. Accessed on 2020-01-04. Beilstein 4 III 1887. Hiromi Ohsaki, Yoshihumi Takeda, Toshinobu Ishihara, and Akira Hayashida (1991)
Method for preparing hexamethyl cyclotrisilazane
. United States Patent 5075474A Barry C. Arkles and Burrell N. Hamon (1985):
Method of preparing hexamethylcyclotrisilazane
United States Patent 4577039A. Dennis W. Hess and Todd A. Brooks (1987):
Plasma enhanced chemical vapor deposition of thin films of silicon nitride from cyclic organosilicon nitrogen
. United States Patent 4863755A. T. A. Brooks and D. W. Hess (1988): "Deposition chemistry and structure of plasma‐deposited silicon nitride films from 1,1,3,3,5,5‐hexamethylcyclotrisilazane". ''Journal of Applied Physics'', volume 64, page 841. T. A. Brooks and D. W. Hess (1987): "Plasma-enhanced chemical vapor deposition of silicon nitride from 1,1,3,3,5,5-hexamethylcyclotrisilazane and ammonia". ''Thin Solid Films'', volume 153, issues 1–3, pages 521-529. NCBI, U.S. National Institutes of Health (2020):
2,2,4,4,6,6-Hexamethylcyclotrisilazane
. Compound data sheet, PubChem online database. Accessed on 2020-01-04. J. Nawrocki (1985): "Modification of silica with mixtures of hexamethylcyclotrisilazane and hexamethyldisilazane". ''Chromatographia´ volume 20, pages 308–312. N. I. Fainer, A. N. Golubenko, Yu. M. Rumyantsev, and E. A. Maximovskii (2009): "Use of hexamethylcyclotrisilazane for preparation of transparent films of complex compositions". ''Glass Physics and Chemistry'', volume 35, issue 3, pages 274–283. Béla Rozsondai, István Hargittai, Aleksei V. Golubinskii, Lev V.Vilkov, and Vladimir S.Mastryukov (1975): "Electron diffraction study on the molecular structure of hexamethylcyclotrisilazane, ". ''Journal of Molecular Structure'', volume 28, issue 2, pages 339-348. D. M. Adams and W. S. Fernando (1973): "The vibrational spectra of hexamethylcyclotrisiloxane and hexamethylcyclotrisilazane". ''Journal of the Chemical Society, Dalton Transactions'', issue 4, pages 410-413.{{doi, 10.1039/DT9730000410 Nitrogen heterocycles Silicon heterocycles

Structure

Synthesis

See also

References