Dinuclear barium(II) complexes based on a calix[4]arene scaffold as catalysts of acyl transfer

Roberta Cacciapaglia, Alessandro Casnati, Stefano Di Stefano, Luigi Mandolini, Daniele Paolemili, David Reinhoudt, A. Sartori, Rocco Ungaro

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    Abstract

    Two novel regioisomeric calix[4]arene derivatives (2 and 3), decorated with two aza[18]crown-6 units at vicinal (1,2) or diagonal (1,3) positions of the upper rim, were synthesized. The catalytic activities of their dinuclear Ba2+ complexes were investigated in the ethanolysis of esters 8-11, endowed with a carboxylate anchoring group. Major results are as follows: 1) the two metal ions in the dinuclear catalysts work together in a cooperative fashion; 2) the vicinal calix[4]arene catalyst 2 is far superior to its diagonal regioisomer 3 in the reactions of all of the investigated esters; and 3) the distance between the carboxylate and ester carbonyl, which increases regularly from 8 to 11, influences reactivity of catalytic ester cleavage in a way that is decidedly suggestive of the importance of a good match between ester size and metal-to-metal distance. However, the superiority of the vicinal catalyst 2 relative to 3 cannot be explained on the basis of the putative match of ester size to intermetal distance, thus providing an indication that additional, still poorly understood effects may contribute significantly to catalytic efficiency.
    Original languageUndefined
    Pages (from-to)4436-4442
    Number of pages7
    JournalChemistry: a European journal
    Volume10
    Issue number18
    DOIs
    Publication statusPublished - 2004

    Keywords

    • Calixarenes
    • IR-49561
    • metallocatalysts
    • METIS-222167
    • Supramolecular Chemistry
    • effective molarity
    • Crown compounds

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