Tris(trimethylsilyl)silane
[CAS# 1873-77-4]

Identification

• Classification: Chemical reagent >> Organic reagent >> Silane
• Name: Tris(trimethylsilyl)silane
• Molecular Formula: C₉H₂₇Si₄
• Molecular Weight: 247.65
• CAS Registry Number: 1873-77-4
• EC Number: 678-629-0
• SMILES: C[Si](C)(C)[SiH]([Si](C)(C)C)[Si](C)(C)C

Properties

• Density: 0.806
• Boiling point: 73 °C (5 mmHg)
• Refractive index: 1.489
• Flash point: 55 °C

Safety Data

• Hazard Symbols: GHS02;GHS07 Danger
• Risk Statements: H225-H315-H319
• Safety Statements: P501-P240-P210-P233-P243-P241-P242-P264-P280-P370+P378-P337+P313-P305+P351+P338-P362+P364-P303+P361+P353-P332+P313-P403+P235

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Flammable liquids	Flam. Liq.	3	H226
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Pyrophoric liquids	Pyr. Liq.	1	H250

• Transport Information: UN 1993

Discovery and Applications

Tris(trimethylsilyl)silane, commonly abbreviated as TTMS or (TMS)₃SiH, is an organosilicon compound that has become an important reagent in organic synthesis due to its unique properties as a free radical mediator and hydrogen donor. Tris(trimethylsilyl)silane was first reported in the early 1980s by researchers seeking a safer and more efficient hydrogen donor than traditional reagents such as tin hydrides. Its discovery provided chemists with a new tool, especially in free radical chemistry where control and selectivity of reduction processes are crucial. Its chemical structure is a central silicon atom bonded to three trimethylsilyl (TMS) groups and a hydrogen atom, and the Si-H bonds in TTMS act as a source of hydrogen atoms in a variety of chemical reactions. It is a colorless liquid that is soluble in common organic solvents such as toluene, hexane, and THF.

TTMS is widely used as a free radical hydrogen donor in organic synthesis. Its ability to efficiently transfer hydrogen atoms makes it well suited for free radical reduction reactions, including the reduction of alkyl and aryl halides, the dehalogenation of polyhalogenated compounds, and the reduction of alkynes to alkenes. The use of TTMS allows for selective reductions under mild conditions, avoiding the harsh reagents and conditions typically required by traditional methods. This selectivity is particularly valuable in complex molecular synthesis, where it is critical to maintain the integrity of functional groups.

In the desulfurization of thioketones and other sulfur-containing compounds, TTMS serves as a clean and efficient hydrogen source to convert these substrates to the corresponding hydrocarbons without generating toxic byproducts. TTMS is used for the deprotection of sensitive functional groups, such as the cleavage of silyl ethers, without affecting other functional groups in the molecule. This property is highly advantageous in multi-step synthetic routes where protecting groups are strategically used.

In complex molecular synthesis, TTMS is used to promote free radical-mediated transformations, such as carbon-carbon and carbon-heteroatom bond formation. Its use improves reaction efficiency and yields, especially in the synthesis of natural products and pharmaceuticals. TTMS is used as a free radical initiator in polymer chemistry to aid in the polymerization of monomers and the modification of polymer structures, aiding the development of advanced materials with tailored properties.

TTMS offers a more environmentally friendly alternative to traditional reagents, such as tin hydrides, which are toxic and generate hazardous waste. Its application reduces the environmental impact of chemical processes and improves the safety of synthetic operations.

In a research setting, TTMS is used to study free radical mechanisms, gaining insights into free radical behavior and the development of new free radical-based reactions. This knowledge has advanced the field of free radical chemistry and broadened the range of synthetic methods. Ongoing research explores new applications of TTMS in a variety of chemical processes, including its role in catalysis, materials science, and emerging technologies.

References

2024. Boryl radical-mediated halogen-atom transfer enables arylation of alkyl halides with electrophilic and nucleophilic coupling partners. Nature Synthesis.
DOI: 10.1038/s44160-024-00587-5

2024. Total synthesis of Comfreyn A and structural analogues via two photochemical key steps. Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology.
DOI: https://pubmed.ncbi.nlm.nih.gov/38935211

2023. Catalytic acceptorless dehydrogenative coupling mediated by photoinduced hydrogen-atom transfer. Nature Synthesis.
DOI: 10.1038/s44160-022-00195-1