Bis(trimethylsilyl)acetylene

Bis(trimethylsilyl)acetylene (BTMSA) is an organosilicon compound with the formula Me₃SiC≡CSiMe₃ (Me = methyl). It is a crystalline solid that melts slightly above room temperature and is soluble in organic solvents. This compound is used as a surrogate for acetylene.

Bis(trimethylsilyl)acetylene

Names
Preferred IUPAC name Ethynediylbis(trimethylsilane)
Other names BTMSA
Identifiers
CAS Number	14630-40-1 Y
3D model (JSmol)	Interactive image
ChemSpider	76286 N
ECHA InfoCard	100.035.141
PubChem CID	84564
CompTox Dashboard (EPA)	DTXSID3065798
InChI InChI=1S/C8H18Si2/c1-9(2,3)7-8-10(4,5)6/h1-6H3 N Key: ZDWYFWIBTZJGOR-UHFFFAOYSA-N N InChI=1/C8H18Si2/c1-9(2,3)7-8-10(4,5)6/h1-6H3 Key: ZDWYFWIBTZJGOR-UHFFFAOYAF
SMILES C(#C[Si](C)(C)C)[Si](C)(C)C
Properties
Chemical formula	C8H18Si2
Molar mass	170.402 g·mol−1
Appearance	Colorless to white liquid
Density	0.791 g/cm3
Melting point	26 °C (79 °F; 299 K)
Boiling point	134.6 ± 8.0 °C (274.3 ± 14.4 °F; 407.8 ± 8.0 K)
Solubility in water	0.031 g/L
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Flammable, Irritant
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

BTMSA is prepared by treating acetylene with butyllithium followed by addition of trimethylsilyl chloride (Me = CH₃, Bu = C₄H₉):^[1]

HC≡CH + 2 BuLi → LiC≡CLi + 2 BuH

LiC≡CLi + 2 Me₃SiCl → Me₃SiC≡CSiMe₃ + 2 LiCl

Applications

BTMSA is used as a nucleophile in Friedel-Crafts type acylations and alkylations and a precursor to lithium trimethylsilylacetylide. The TMS groups can be removed with tetra-n-butylammonium fluoride (TBAF) and replaced with protons. BTMSA is also a useful reagent in cycloaddition reactions. Illustrating its versatility, BTMSA was used in a concise total synthesis of (±)-estrone.^[2] A key step in this synthesis was the formation of the steroidal skeleton, catalyzed by CpCo(CO)₂.

BTMSA also serves as a ligand in organometallic chemistry. For example, it forms stable adducts with metallocenes.^[3]

Cp₂TiCl₂ + Mg + Me₃SiC≡CSiMe₃ → Cp₂Ti[(CSiMe₃)₂] + MgCl₂