Manganese(II), Nickel(II), and Palladium(II) Complexes of a Terpyridine-Like Ligand Containing a Sulfur Linkage, and an Analogous NCN Pincer Palladium(II) Complex: Synthesis, Characterization, and Pd-Catalyzed Reactions

Abstract

Abstract Coordination properties of new polypyridines containing a single sulfur linkage, 6-(2′′-pyridylthio)-2,2′-bipyridine (L1) and 1-(2′-pyridyl)-3-(2′′-pyridylthio)benzene (HL2), are described. The manganese(II) and nickel(II) complexes of the terpyridine-like ligand L1, [MnCl2(L1)] (1), [NiCl(μ-Cl)(L1)]2 (2), and [Ni(L1)2](SbF6)2 (3), were prepared and characterized by UV–vis spectroscopy and X-ray crystallography. The palladium(II) complex [PdCl(L1)]Cl (4) was synthesized from L1 and Li2[PdCl4] at room temperature, while the corresponding NCN pincer complex of L2, [PdCl(L2)] (5), was synthesized in DMSO at 150 °C by cyclopalladation of the ligand precursor HL2. The crystal structures of 4 and 5 revealed similar coordination geometries around Pd except for the longer Pd–Cl distance in 5, which is induced by the strong trans influence of the Pd–C bonding. The NMR spectra of 4 showed partial dissociation of L1 in DMSO-d6, which was not observed for L2 in 5. Catalytic activities of 4 and 5 for the Mizoroki–Heck reaction were investigated, and the lower activity of 5 can be related to the strong σ-donating character of L2.