Pd2L2 metallacycles as molecular containers for small molecules?

Dalton Transactions Pub Date: 2010-10-21 DOI: 10.1039/C0DT00406E

Abstract

M2L2 type metallacyclic complexes, [Pd2(L1)2Cl4]·1.5CH2Cl2 (1), [Pd2(L1)2Cl4]·2CHCl3 (2), [Pd2(L2)2Cl4]·2CH2Cl2·2CH3CN (3), [Pd2(L2)2Cl4]·2CHCl3·2CH3CN (4) and [Pd2(L3)2Cl4]·CH2Cl2·2CH3CN (5), have been prepared from three semi-rigid benzimidazol or benzotriazol ligands, 1,4-bis(benzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene (L1), 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene (L2) and 1,4-bis(benzotriazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene (L3). All the complexes were structurally characterized by single-crystal X-ray diffraction and the phase purity was confirmed by powder X-ray diffraction (PXRD) measurements. The solution structure of representative complex 1 was studied by 1H NMR titration and ESI mass spectroscopy. The thermal stability and guest-exchange properties of 1, 3 and 4 were investigated, revealing that the Pd2L2 metallacycles can act as a selective receptor for CH2Cl2 or CHCl3 guest molecules. The catalytic activity of 1 in Suzuki–Miyaura coupling reaction was also studied and 1 could be recycled at least 5 times under heterogeneous conditions, indicative of a potential self-supported catalyst.

Graphical abstract: Pd2L2 metallacycles as molecular containers for small molecules
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