Synthesis and characterisation of pyrazolic palladium compounds containing alcohol functionality:: rotation around the Pd–N bond

The ligands 1-hydroxymethylpyrazole (hl1), 1-(2-hydroxyethyl)pyrazole (hl2) and 1-(3-hydroxypropyl)pyrazole (hl3) react with [PdCl2(CH3CN)2] to give trans-[PdCl2(hl)2] compounds. Due to a hindered rotation around the Pd-bond, these compounds present two different conformations in solution: anti and syn. The conformation presented depends on the relative disposition of the hydroxyalkylic chains of the two pyrazolic ligands. The present study was carried out on the basis of NMR experiments. The present paper reports the crystal structure of trans-[PdCl2(hl2)2]. The synthesis and characterisation of compounds [Pd(hl)4](BF4)2 (hl = hl1, hl2 and hl3) starting from [Pd(CH3CN)4](BF4)2 and the corresponding chlorocomplexes trans-[PdCl2(hl)2] are also described.