Stereoselective formation and properties of mononuclear and polynuclear nickel(II) complexes with 1-amino-2-propanethiolate

Abstract

Abstract A mononuclear complex acting as a novel chiral ligand, [Ni(1-Meaet)2] (1-Meaet = 1-amino-2-propanethiolate; 1b) was synthesized. Using this mononuclear complex, the S-bridged trinuclear complex [Ni{Ni(1-Meaet)2}2]2+ (2b), hexanuclear complex [Pd2{Ni0.6Pd0.4(1-Meaet)2}4]4+ (3b), and dinuclear complexes [Pt(bpy){Ni(1-Meaet)2(H2O)2}]2+ (bpy = 2,2′-bypyridine; 4b) and [Pt(bpy){Ni(1-Meaet)(bpy)}]2+ (5b) were synthesized. Molecular structures for 3b and 5b were determined by X-ray diffraction. In the crystal structure of 3b, two Pd(II) ions are bridged by four metalloligands, cis(S)-[Ni(1-Meaet)2] and/or cis(S)-[Pd(1-Meaet)2] units, forming a C4h symmetrical S-bridged hexanuclear structure with high optical selectivity of the ligand, in which all [M(1-Meaet)2] units have the absolute cis(S)-R,S configuration. In the crystal structure of 5b, the Ni(II) ions are surrounded by two 1-Meaet and one bpy to have an approximately octahedral geometry with 50% ligand diastereoselectivity of the mixed crystals of ΔRR/ΛSS and ΔRS/ΛRS configuration. Moreover, the lowering of the nucleophilicity of the sulfur atom was observed by the introduction of the methyl group. The properties of 1b–5b were discussed in comparison with the corresponding aet (2-aminoethanethiolate) complexes 1a–5a using X-ray absorption, UV/Vis, IR, far-IR, Raman and NMR spectra, as well as structural analysis.