Synthesis and characterization of organopalladium(II) complexes of N,N,S–tridentate sulfur-containing Schiff bases derived from 2-(2-pyridyl)benzothiazolines

Abstract

The synthesis of mononuclear Pd(II) complexes of type [Pd(Ln)Me] (n = 1–4, 1a–4a) and dinuclear (η3–allyl)palladium(II) dichloro complexes [Pd2(Ln)(η3-C3H5)Cl2] (n = 1–3, 1b–3b) derived from 2-R-(2-pyridyl)benzothiazolines used as Schiff bases precursors (R = H, 1; R = Me, 2; R = Ph, 3; R = C5H4N-2, 4) is reported. The formation of the trinuclear complex [Pd3(L4)(η3-C3H5)2Cl3] (4c) and its behavior in solution is also described. Complexes 1a–4a, 1b–3b and 4c were obtained from the thiazole ring-opening reaction of precursors 1–4 in presence of the [Pd(tmeda)Me2] and [Pd(μ -Cl)(η3-C3H5)]2 starting materials. The {Ln}− anionic Schiff bases obtained showed a versatile behavior towards coordination to Pd(II) ion; in 1a–4a the ligand acted as tricoordinate whilst in 1b–3b and 4c, {Ln}− acted as mono- and tridentate ligand, respectively.1a–4a were stable complexes in DMSO‑d6 solution; the dinuclear 1b–3b and trinuclear 4c complexes showed the dissociation of S→Pd bond in DMSO‑d6 solution. Complexes 3a and 3b were characterized by X-ray diffraction studies and a distorted square planar geometry around the central Pd(II) ion was observed in the two five–membered chelate rings. A systematic analysis based on DFT calculation of the structural, electronic, and thermochemistry properties was performed for η3-ally complexes 1b–3b and 4c.