Variable Coordination Behavior of New Hybrid Pyrazole Ligand: Synthesis and Characterization of Several ZnII, CdII, HgII, PdII, PtII, and NiII Complexes

Abstract

In this paper we describe the synthesis of the new mixed-donor ligand 1,8-bis(3,5-dimethyl-1H-pyrazol-1-yl)-3,6-dioxaoctane (L). The complexes [MCl(2)(L)] (M = Zn(II) (1), Cd(II) (2), Hg(II) (3), Pd(II) (4), Pt(II) (6), Ni(II) (7)) and [PdCl(2)(L)](2) (5) were prepared and fully characterized. X-ray crystal structures of complexes 1, 2, 4, 6, and 7 have been determined. The L ligand behaves either as a NN-bidentate (chelate or bridge) and NOON-tetradentate (equatorial or planar) ligand. In these structures, C-H...X (X = O, N or Cl/Cl(-)) intermolecular interactions have been identified and studied. Moreover, the (113)Cd{(1)H}, (195)Pt{(1)H}, and (199)Hg{(1)H} NMR spectra were measured to investigate the coordination environment of the metal in solution. Diffusion NMR studies have also been performed to characterize monomeric and dimeric species of Pd(II). Finally, we have observed that the dimeric complex 5 is converted into the corresponding monomeric complex 4.