Synthesis, characterization and X-ray crystal structure determination of cyclopalladated [Csp²,N,N′]^-, zwitterionic and chelated compounds in the reaction of 3,5-diphenyl-N-alkylaminopyrazole derived ligands with Pd(II)

The synthesis of two N-alkylaminopyrazole ligands, 1-[2-(diethylamino)ethyl]-3,5-diphenylpyrazole (L1) and 1-[2-(dioctylamino)ethyl]-3,5-diphenylpyrazole (L2), is reported. These ligands present, a priori, one pyrazole nitrogen and one amine nitrogen as potential donor atoms. However, in the reaction of the ligands (L1 and L2) with [PdCl2(CH3CN)2] one of the Cphenyl atoms can also behave as a donor atom. As a result, we have obtained the formation of three different compounds for each one of the ligands: chelated ([PdCl2(L)] L = L1 (1a), L2 (2a)), zwitterionic ([PdCl3(LH)] LH = LH1 (1b), LH2 (2b)), and cyclopalladated compounds ([PdCl(LC)] (LC = LC1 (1c), LC2 (2c)). The solid-state structures for 1a, 1b and 1c were determined by single crystal X-ray diffraction methods. The potentially [C,N,N′]- ligand is coordinated through the Npz and the Namino to the metal atom for 1a, through the Npz for 1b, and through the Npz, the Namino and a Cphenyl for 1c. © 2008 Elsevier B.V. All rights reserved.