Synthesis of new palladium(II) complexes containing tetradentate-nitrogen donor ligands: Combined structural studies by NMR spectroscopy and X-ray crystallography

Treatment of the tetradentate (NN′N′N) N-alkylaminopyrazole ligands 3,6-dimethyl-1,8-(3,5-dimethyl-1-pyrazolyl)-3,6-diazaoctane (ddad) and 1,4-bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]piperazine (bedp) with [PdCl2(CH3CN)2] in a 1:1 M/L ratio in acetonitrile produces [Pd2Cl4(L)] and [PdCl2(L)] (L = ddad and bedp). Treatment of the corresponding complex [PdCl2(L)] (L = ddad, bedp) in the presence of AgBF4 in CH2Cl2/methanol (2:1) or NaBF4 in acetonitrile gives [Pd(L)](BF4)2. The Pd(II) complexes have been characterised by elemental analyses, conductivity measurements, IR and 1H and 13C{1H} NMR spectroscopies when possible. The X-ray structure of the complex [Pd(ddad)]Cl2 · 3H2O has been determined. The Pd(II) is coordinated to the ddad ligand by two nitrogen atoms of pyrazolyl groups and two nitrogen atoms of the amine groups, in a slightly distorted square-planar geometry. © 2007 Elsevier B.V. All rights reserved.