1968 Volume 41 Issue 5 Pages 1194-1200
Seven haloalcoholates of aluminum and zinc were prepared by the reactions of haloalcohols with metal alky Is in ethyl ether, and their properties were examined. The following differences have been observed between these haloalcoholates and the usual alcoholates, those with no halogen in the alkyl groups. (1) The metal haloalcoholates are unstable to heat and decompose at 90–220°C. Except for Al(OCH2CF3)3, they are neither distilled nor sublimed even in vacuo. The usual aluminum alcoholates, such as ethoxide and isopropoxide, are easily distilled under reduced pressures. (2) The haloalcoholates are stronger Lewis acids than the usual alcoholates. The acid strength of some aluminum haloalcoholates is even higher than triethylaluminum. The strong acid nature of the aluminum haloalcoholate can be ascribed to the electron-withdrawing effect of halogen. (3) As expected from their strong acid strength, the haloalcoholates induce the cationic polymerizations of vinyl monomers and cyclic ethers, such as styrene, α-methylstyrene, isobutyl vinyl ether, 3,3-bis-(chloromethyl)oxacyclobutane, and tetrahydrofuran. The usual metal alcoholates are weaker acids and do not cause the polymerizations of these monomers. In the ethylene oxide polymerization, both the haloalcoholates and the usual alcoholates showed catalytic activity. However, these two types of alcoholates differ from each other in the catalysis mechanism. For the polymerization of ethylene oxide by the haloalcoholate catalyst, a cationic polymerization mechanism was assumed on the basis of the formation of dioxane as a by-product. The polymerization by the usual alcoholate catalysts is assumed to be of a coordinate anionic mechanism.
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