Silicon Tetrafluoride SiF

You may know that hydrofluoric acid dissolves glass. But HF is not a strong acid. The reaction of glass with hydrofluoric acid occurs because silicates react with HF to produce silicon tetrafluoride, SiF, a very volatile compound. This reaction tells us nothing about the acid strength of hydrofluoric acid. 

Sir Humphry Davy attempted to isolate this unidentified element through electrolysis—but failed. It was not until 1824 that Jons Jakob Berzehus (1779—1848), who had earlier discovered cerium, osmium, and iridium, became the first person to separate the element silicon from its compound molecule and then identify it as a new element. Berzehus did this by a two-step process that basically involved heating potassium metal chips with a form of silica (SiF = silicon tetrafluoride) and then separating the resulting mixture of potassium fluoride and silica (SiF + 4K —> 4KF + Si). Today, commercial production of sihcon features a chemical reaction (reduction) between sand (SiO ) and carbon at temperatures over 2,200°C (SiO + 2C + heat— 2CO + Si). 

Fluorosilicates syn. silicofluorides are those salts containing either the SiF or the SiF5 species involving silicon and fluorine including sodium fluorosilicate. Fluorosilicates are often toxic and react with acids to give hydrogen fluoride and silicon tetrafluoride. 

Ethylene oxide reacted with silicon tetrafluoride at -78 in a vacuum to produce a white solid complex, SiF [(CH )20]2, the composition of which was confirmed by quantitative synthesis and tensimetric titration. Attempts to measure dissociation pressures of the adduct were unsuccessful because it dissociated and decomposed slowly above -78° and rapidly at -45° into 1,4-di-oxane, a non-volatile polymer, and silicon tetrafluoride. This type of... 

Silicon tetrafluoride s. under AlClg Titanium tetrafluoride s. under SF SiF, TiF ... 

Few coordination compounds of silicon and germanium tetrafluoride have been prepared and characterized. MUETTERTIES (1) has described SiF [(CH ) SO] and SiF [(CH )2NCHO]2 and the corresponding complexes of germanium tetrafluoride. ISSLEIB and REINHOLD (2) have prepared SiF [(C Hg) PO], ... 

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