Divergent Solution and Solid-State Structures of Mono- and Dinuclear Nickel(II) Pyridone Complexes

The chelating 2-pyridone ligand (E)-6-(1-((2-(methylthio)phenyl)imino)ethyl)pyridin-2(1H)-one (1) has been used to synthesize five nickel(II) complexes that have been characterized by single-crystal X-ray diffraction, UV/vis and IR spectroscopies, and benchtop magnetometry. Reaction of NiX2 (X = BF4, Cl) with 1 yielded the C2-symmetric halide-bridged Ni dimers [(μ-F)Ni2(κN,N,O-1–)2(κN,N-1)2](BF4) (2) and [(μ-Cl)Ni2(κN,N,O-1–)2(κN,N-1–)(κN,N-1)] (3), where 2 is formed via a rare example of fluoride abstraction from BF4– by a transition metal. Remarkably, the reaction of Ni(OAc)2 with 1 followed by different methods of crystallization yielded three different products: the dimer [(μ-OH2)Ni2(κN,N,O-1–)(κN,N-1–)(κN,N-1)(OAc)2] (4), as well as the monomers [Ni(κN,N-1–)2(MeOH)2] (5) and [Ni(κN,N-1–)(κN,N-1)(OAc)(OH2)] (6). This observation is emblematic of the soft energy landscape of coordination motifs and nuclearity that pyridone ligands provide with late 3d transition metals. To better understand the solutio...