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

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Cacciapaglia, Roberta and Casnati, Alessandro and Di Stefano, Stefano and Mandolini, Luigi and Paolemili, Daniele and Reinhoudt, David N. and Sartori, Andrea and Ungaro, Rocco (2004) Dinuclear barium(II) complexes based on a calix[4]arene scaffold as catalysts of acyl transfer. Chemistry: a European Journal, 10 (18). pp. 4436-4442. ISSN 0947-6539

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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.
Item Type:Article
Copyright:© 2004 WILEY-VCH Verlag
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Link to this item:http://purl.utwente.nl/publications/49561
Official URL:http://dx.doi.org/10.1002/chem.200400294
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Metis ID: 222167