Calix[4]arene-based Zn2+ complexes as shape- and size-selective catalysts of ester cleavage.
[structures: see text] The kinetics of methanolysis of a number of esters endowed with a carboxylate anchoring group have been investigated in the presence of di- and trinuclear Zn2+ complexes of calix[4]arenes functionalized at the upper rim with nitrogen ligands. The results (i) emphasize the importance of a good match between ester size and intermetal distance, (ii) reveal a substrate independent superiority of the 1,2-vicinal dinuclear catalyst 1-Zn2 to its 1,3-distal regioisomer 2-Zn2, and (iii) provide further evidence for the concurrence of the three metal ions of 3-Zn3 in the catalytic mechanism.
Dipartimento di Chimica and IMC-CNR Sezione Meccanismi di Reazione, Università di Roma La Sapienza, Box 34, Roma 62, 00185 Roma, Italy.
Roberta
R
Cacciapaglia
Alessandro
A
Casnati
Luigi
L
Mandolini
David N
DN
Reinhoudt
Riccardo
R
Salvio
Andrea
A
Sartori
Rocco
R
Ungaro