Abstract
AbstractThe synthesis and characterization of aluminum alkoxide and alkyl complexes stabilized by piperazidine‐bridged bis(phenolate) ligands are described. Treatment of ligand precursors H2[ONNO]1 {H2[ONNO]1=1,4‐bis(2‐hydroxy‐3‐tert‐butyl‐5‐methylbenzyl)piperazidine} and H2[ONNO]2 {H2[ONNO]2=1,4‐bis(2‐hydroxy‐3,5‐di‐tert‐butylbenzyl)piperazidine} with AlEt2(OCH2Ph) and AlEt2(OPr‐i), which were generated in situ by the reactions of AlEt3 with equivalent of the corresponding alcohols, in a 1:1 molar ratio in THF gave the corresponding aluminum alkoxide complexes [ONNO]1Al(OCH2Ph) (1) and [ONNO]2Al(OPr‐i) (2), respectively. The reaction of H2[ONNO]1 with AlEt2(OCH2Ph) in a 1:2 molar ratio in THF afforded a mixture of monometallic aluminum ethyl complex [ONNO]1AlEt (3) and complex 1, which can be isolated by stepwise crystallization. Similarly, H2[ONNO]2 reacted with AlEt2(OPr‐i) in a 1:2 molar ratio in THF to give a mixture of aluminum ethyl complex [ONNO]2AlEt (4) and complex 2. Complexes 1 and 2 were also available via treatment of complexes 3 and 4 with 1 equiv. of benzyl alcohol and isopropyl alcohol, respectively. All of these complexes were fully characterized including X‐ray structural determination. It was found that complexes 1 to 4 can initiate the ring‐opening polymerization of ε‐caprolactone, and complexes 1 and 2 showed higher catalytic activity in comparison with complexes 3 and 4.
Published Version
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