Silicon tetraacetate

This procedure for the preparation of silicon tetraacetate was discovered by Friedel and Ladenburg 1 however, details of their work were not published, and subsequent workers appear to have adopted more complicated methods. The procedure given here is also applicable to the preparation of alkyl- or arylacetoxysilanes of the type RnSi(C2H302).i from organochlorosilanes. 

The silicon tetraacetate is twice recrystallized by dissolving it in acetic anhydride at 100°f and cooling to 0°. 

The first recrystallization requires 100 ml. of solvent, and the second, 75 ml. While still in the reaction flask, the purified silicon tetraacetate is subjected to a preliminary drying at room temperature in vacuo it is then dried further at 100° for several hours. The yield is 335 g. (84.6%, based on silicon tetrachloride). 

Silicon tetraacetate is a colorless, crystalline solid, which reacts vigorously with water and hydrolyzes rapidly when exposed to moist air. It melts at HO01 and decomposes at 160 to 170° with evolution of acetic anhydride.1 It is moderately soluble in inert organic liquids such as acetone and benzene. 

Iron(II) bromide 6-am-moniate, synthesis 53 Acidopentamminecobalt-(III) salts, synthesis 56 Nitrosylpentammine-cobalt(II) chloride, synthesis 55 

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The substance is a little discolored when distilled because of slight decomposition which becomes appreciable at 160°-170°C, with the evolution of acetic anhydride. Silicon tetraacetate is vigorously decomposed by water but it dissolves to a moderate extent in inert liquids such as acetone and benzene. With ethyl alcohol it forms ethyl acetate and silicon dioxide as products of alcoholysis. 

See also Silicon tetrachloride) Silicon compounds, halomethyl derivatives by the diazomethane method, 6 37, 39 nomenclature of, 2 265 organo-, 3 50 nomenclature of, 3 55 Silicon tetraacetate, 4 45 Silicon tetrabromide, 1 38, 40 Silicon tetrachloride, 1 44 Silicon tetrafluoride, 4 145 Silicooxalic acid, (H Si, ,), formation of, by disilicon hexa-bromide, 2 101... 

The mother liquor may be separated from the produet by distillation however, this leads to discoloration of the silicon tetraacetate. For this reason, purification by recrystallization is preferable. When the procedure given here is applied to the preparation of organoacetoxysilanes, distillation is usually necessary. In this case, the acetyl chloride is removed at atmospheric pressure, and the excess acetic anhydride and product are separated by fractional distillation under reduced pressure. 

Si(CH=CH2)2Cl2 Silane, divinyl-dichloro-, 3 58, 61 Si(C2H302)4 Silicon tetraacetate, 4 45... 

T. Maruyama and J. Shionoya, Silicon Dioxide Films Prepared by Chemical Vapour Deposition from Silicon Tetraacetate , Jap. J. Appl. Rhys., 28 [12] L2253-54 (1989). 

Silicon tetraacetate [562-90-3] M 2643, m 110-111 , b 148 /5-6mm, pKf 9.7, pKf 11.9 (for 048104 free acid). It can be crystallised from mixtures of CCI4 and pet ether or Et20, or from acetic anhydride and then dried in a vacuum desiccator over KOH. A02O adheres to the crystals and is removed first by drying at room temperature, then at 100 for several hours. It is soluble in Me2CO, is very hygroscopic and effervesces with H2O. It decomposes at 160-170 . [Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 7011963, Beilstein 2 H 171.]... 

Substituting silicon tetraacetate, Si(OAc)4, for TEOS in a typical sol-gel reaction (monomer ethanol = 1 4, mixed 30 min prior to addition of 4 mol of 1.0 M HCl) results in a decrease in gel time from 242 to 1 h (27). This decrease is attributed to the generation of Si02 by direct attack of alcohol on the bound acetates. However, recent work (30) shows that... 

Silicon tetraacetate may be prepared by the reaction between SiCl4 and acetic anhydride and has a structure comprising discrete molecules with no bridging by acetate, although there is one short intramolecular distance between a carbonyl oxygen and the silicon in each molecule. 

SiGl4 allowed to react with excess terf-butyl acetate at room temp. silicon tetraacetate. Y almost 100%. R. C. Mehrotra and B. C. Pant, Tetrah. Let. 1965,321. ... 

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