Synthesis and characterisation of palladium compounds with new polyetherpyrazole ligands

The present report is on the synthesis of new 3,5-dimethylpyrazolic derived ligands that are N1-substituted by polyether chains: 1-(2-methoxyethoxymethyl)-3,5-dimethylpyrazole (L1), 1-[2-(2-methoxyethoxymethoxy)ethyl]-3,5-dimethylpyrazole (L2) and 1-[2-[2-(2-methoxyethoxy)ethoxy]ethyl]-3,5-dimethylpyrazole (L3). These ligands form complexes with the formula [PdCl2L2] when reacting with [PdCl2(CH3CN)2] in the ratio 1M:2L. Two crystalline structures have been resolved with ligands L1 and L3, where the Pd(II) presents a square planar geometry with the ligands co-ordinated in a trans disposition. NMR studies prove the existence of two conformational diastereoisomers for each complex in solution, as a consequence of the slow rotation around the Pd–N bond: syn and anti. The reaction of ligands L1, L2 and L3 with [PdCl2(CH3CN)2] in presence of AgBF4 yields the compounds [PdClL3]BF4, characterised by elemental analysis, conductivity measurements, 1H NMR, 13C{1H} NMR, infrared spectra, and FIA ES(+)/MS. [Copyright &y& Elsevier]