1450-14-2

Preparation

Hexamethyldisilane is produced by the reaction of methyl Grignard reagent with methylchlorodisilanes. This reaction is normally conducted in the presence of an ether such as diethyl ether, ethyl propyl ether, THF and the like.

Fire Hazard

Hexamethyldisilazane (HMDZ) is a highly flammable liquid and vapour. HMDZ liquid is lighter than water and may float on water, spreading material during fire fighting. Leaking material or fire runoff to sewer may create fire or explosion hazard. HMDZ vapours are heavier than air and can accumulate to form explosive concentrations. The vapours may also spread a considerable distance to a source of ignition, and flash back towards the source. HMDZ reacts with water to form ammonia. HMDZ is a non-conductor and, therefore, can accumulate static electrical charges when processed, handled or dispensed. HMDZ's flash point is 52 to 53°F, closed cup, for "pure" material.

Purification Methods

The most likely impurity is trimethylchlorosilane (cf boiling point). Wash it with H2O, cold conc H2SO4, H2O again, then aqueous NaHCO3, dry over CaSO4 and fractionate at atmospheric pressure. [Brown & Fowles J Chem Soc 2811 1958.] A grossly impure sample (25% impurities) was purified by repeated spinning band distillation. This lowered the impurity level to 500ppm. The main impurity was identified as 1-hydroxypentamethyldisilane. [Beilstein 4 IV 4277.]

Application

Hexamethyldisilane is an important silane protective agent, which can synthesize sodium trimethylsilane, potassium trimethylsilane and lithium trimethylsilane.Preparation of iodotrimethylsilane.Used as trimethylsilane anion reagent.silylating or reducing reagent in combination with a Pd catalyst or a nucleophile.Replaces aromatic nitriles with TMS groups in presence of [RhCl(cod)]2.Precursor for CVD of silicon carbide.Brings about the homocoupling of arenesulfonyl chlorides in the presence of Pd2(dba)3.Used as a solvent for the direct borylation of fluoroaromatics.Reacts with alkynes to form siloles.Undergoes the silylation of acid chlorides to give acylsilanes.