Trimethylsilyl iodide

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

Trimethylsilyl iodide

Names
Preferred IUPAC name Iodotri(methyl)silane
Other names Iodotrimethylsilane; TMSI; TMS-I; Jung reagent
Identifiers
CAS Number	16029-98-4
3D model (JSmol)	Interactive image
ChemSpider	76879
ECHA InfoCard	100.036.503
PubChem CID	85247
UNII	7A65KRZ6NV Y
CompTox Dashboard (EPA)	DTXSID4065997
InChI InChI=1S/C3H9ISi/c1-5(2,3)4/h1-3H3 Key: CSRZQMIRAZTJOY-UHFFFAOYSA-N InChI=1/C3H9ISi/c1-5(2,3)4/h1-3H3 Key: CSRZQMIRAZTJOY-UHFFFAOYAB
SMILES I[Si](C)(C)C
Properties
Chemical formula	C3H9ISi
Molar mass	200.094 g·mol−1
Appearance	Clear colorless liquid[1]
Density	1.406 g/mL[1]
Boiling point	106–109 °C (223–228 °F; 379–382 K)[1]
Hazards
Flash point	−31 °C (−24 °F; 242 K)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

Trimethylsilyl iodide may be prepared by the oxidative cleavage of hexamethyldisilane by iodine^[2] or by the cleavage of hexamethyldisiloxane with aluminium triiodide.^[2][3]

TMS-TMS + I₂ → 2 TMSI (TMS = (CH₃)₃Si)

3 TMS-O-TMS + 2 AlI₃ → 6 TMSI + Al₂O₃

Applications

Trimethylsilyl iodide is used to introduce the trimethylsilyl group onto alcohols (ROH):

R-OH + TMSI → R-OTMS + HI

This type of reaction may be useful for gas chromatography analysis; the resultant silyl ether is more volatile than the underivatized original materials.^[4] However, for the preparation of bulk trimethylsilylated material, trimethylsilyl chloride may be preferred due to its lower cost.

TMSI reacts with alkyl ethers (ROR′), forming silyl ethers (ROSiMe₃) and iodoalkanes (RI) that can be hydrolyzed to alcohols (ROH).^[5]

Trimethylsilyl iodide is also used for the removing of the Boc protecting group,^[2][6][7] especially where other deprotection methods are too harsh for the substrate.^[8]