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Monomer-bound ion pairs in the stereoregular polymerization of propylene oxide by the Pruitt-Baggett catalyst

Aksoy, S.
Altinok, H.
Tümtürk, H.
Alyürük, K.
The Pruitt-Baggett adduct (PBA) (MW = 438 g mol−1) that formed from the reaction of FeCl3 with propylene oxide (PO) was hydrolysed in diethyl ether (ether) solutions at different molar ratios. The hydrolysates (), which were insoluble in ether, could be converted into catalytically active form () by a thermal treatment. was soluble in etheric solvents and in pyridine. These solutions, in contrast to PBA and , were electrical conductors. Profound differences in the electrical conductivity of was observed by varying the hydrolysis ratio r. The observed conductivity decayed and finally vanished with a kinetically second-order process. This is explained by the free ions, formed from (MW = 4400 g mol−1), being bound together with an ether (or PO) molecule to yield ether- (or PO-) bound ion pairs (PBCB). and the electrical conductivity of its freshly prepared solutions could be retrieved by ‘driving off’ (by drying under vacuum at 40°C) the ‘binding molecule’ (ether or PO) from PBCB. In contrast to this system, the electrical conductivity of solutions of (which shows inferior catalytic activity) did not change with ageing.