Exploring the coordination chemistry and reactivity of hemilabile N-alkylaminopyrazole ligands towards Pd(II)

Abstract

Reaction of the N-alkylaminopyrazole ( NN′ N) ligands bis[(3,5-dimethyl-1-pyrazolyl)methyl]ethylamine ( bdmae) and bis[(3,5-dimethyl-1-pyrazolyl)methyl]isopropylamine ( bdmai) with [PdCl 2(CH 3CN) 2] in a 1:1 M/L ratio in CH 2Cl 2 produces cis-[PdCl 2( NN′ N)] ( NN′ N = bdmae ( 1), bdmai ( 2)). The solid state structure of complex 1 was determined by X-ray diffraction studies. The bdmae ligand is coordinated through the two N pz atoms to the metal atom, which completes its coordination with two chlorine atoms in a cis disposition. Treatment of the corresponding ligand with [PdCl 2(CH 3CN) 2] in 1:1 M/L ratio in the presence of AgBF 4 and metathesis with NaBPh 4 in CH 2Cl 2/CH 3OH (3:1) gave [PdCl( bdmae)](BPh 4) ( 3), and in the presence of NaBPh 4 in CH 2Cl 2/CH 3CN (3:1) gave [PdCl( bdmai)](BPh 4) ( 4). Complexes 1 and 2 were again obtained when complexes 3 and 4 were heated under reflux in a solution of Et 4NCl in acetonitrile. These Pd(II) compounds were characterised by elemental analyses, conductivity measurements, IR, 1H and 13C{ 1H} NMR, HMQC and NOESY spectroscopies. The NMR studies of the complexes prove the rigid conformation of the ligands when they are complexed.