Synthesis of new palladium(II) complexes containing hemilabile N-(alkylamino)pyrazole ligands: Spectroscopic analysis and crystal structure of PdCl(ddae)Cl·H<inf>2</inf>O {ddae = Bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]ethylamine}

Treatment of the tridentate (NN′N) N-alkylaminopyrazole ligands bis [2-(3,5-dimethyl-1-pyrazolyl) ethyl]ethylamine (ddae), bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]isopropylamine (ddai) and bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]tert-butylamine (ddat) with [PdCl2(CH3CN)2] in a 1:1 M/L ratio in CH2Cl2 produces [PdCl2(NN′N)]. Treatment of the corresponding ligand with [PdCl2(CH3CN)2] in a 1:2 M/L ratio in the presence of AgBF4 in CH2Cl2/methanol (6:1) gives [PdCl(NN′N)](BF4). The complexes [PdCl2(NN′N)] were again obtained when the complexes [PdCl(NN′N)](BF4) were heated under reflux in a solution of NEt4Cl in acetonitrile, which means that ligands ddae, ddai and ddat in complexes 1-6 are hemilabile. These PdII complexes have been characterised by elemental analyses, conductivity measurements and IR and 1H and 13C{1H} NMR spectroscopy. The 1H NMR spectroscopic studies for compounds [PdCl2(NN′N)] give evidence of κ2(Npz,Npz) coordination in acetonitrile and κ3(Npz,Namino,Npz) coordination in methanol. The X-ray structure of the complex [PdCl(ddae)]Cl·H2O has been determined. The PdII is coordinated to the ddae ligand by two nitrogen atoms of the pyrazolyl groups and one nitrogen atom of the amine, along with one chlorine atom, in a slightly distorted square-planar geometry. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.