|Preferred IUPAC name
1,1,3,3,5,5-Hexamethyl-2,4,6,1,3,5-triazatrisilinane; 2,4,4,6,6-Hexamethyl-1,3,5-triaza-2,4,6-trisilacyclohexane; Dimethylsilazane trimer; HMCTS; HCMTSZ
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||219.510 g·mol−1|
|Density||d20 0.9196 g/mL |
|Melting point||−10 °C |
|Boiling point||188 °C |
Refractive index (nD)
|n20/D 1.445 |
|H226, H302, H314, H315, H319, H335|
|P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P330, P332+P313, P337+P313, P362, P363, P370+P378, P403+P233, P403+P235, P405, P501|
|Flash point||59 °C; 139 °F; 333 K|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|500 mg/kg (rat)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Hexamethylcyclotrisilazane is a chemical compound with formula C
3 or [–Si(CH
3. Its molecule consists of a six-member ring of three silicon atoms alternating with three nitrogen atoms, with two methyl groups bonded to each silicon and one hydrogen atom bonded to each nitrogen. It can be described as a derivative of the hypothetical compound cyclotrisilazane [–SiH
3, or as a cyclic trimer of hypothetical dimethylsilazane (CH
The compound is a clear colorless liquid at room temperature.
The compound has been extensively studied because of its applications in the semiconductor industry, as a precursor for the deposition of fils of silicon nitride and silicon carbonitride and as an additive in photoresist formulations. It has also been proposed as an additive to silica for liquid chromatography.
Other names for the compound are 2,2,4,4,6,6-hexamethyl-1,3,5,2,4,6-triazatrisilinane (IUPAC), 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.
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°.
The compound was obtained in 1948 by Brewer and Haber by introducing dimethyldichlorosilane Si(CH
2 into liquid ammonia NH
3, and then extracting the precipitate with benzene. The reaction yields a mixture of compounds, chiefly the trimer and the tetramer octamethyltetrasilazane. The trimer can be separated from the other products by fractional distillation.
- 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. doi:10.1021/ja01191a106
- 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.
- FAR Chemical (2020): "Product 654201: Hexamethylcyclotrisilazane". Catalog page. Accessed on 2020-01-04.
- Beilstein 4 III 1887.
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- J. Nawrocki (1985): "Modification of silica with mixtures of hexamethylcyclotrisilazane and hexamethyldisilazane". Chromatographia´ volume 20, pages 308–312. doi:10.1007/BF02310388
- Béla Rozsondai, István Hargittai, Aleksei V. Golubinskii, Lev V.Vilkov, and Vladimir S.Mastryukov (1975): "Electron diffraction study on the molecular structure of hexamethylcyclotrisilazane, [(CH
3". Journal of Molecular Structure, volume 28, issue 2, pages 339-348. doi:10.1016/0022-2860(75)80104-9
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