title: Solid-state spin crossover of Ni(II) in a bioinspired N3S2 ligand field.
abstract: The complex Tp(Ph,Me)NiS(2)CNMe(2) [Tp(Ph,Me) = hydrotris(3-phenyl-5-methyl-1-pyrazolyl)borate] features a bioinspired N(3)S(2) ligand set supporting a five-coordinate, trigonally distorted square-pyramidal geometry in the solid state. Spin crossover of Ni(II) was demonstrated by temperature-dependent X-ray crystallography and magnetic susceptibility measurements. The crystal lattice contains two independent molecules (i.e., Ni1 and Ni2). At 293 K, the observed bond lengths and susceptibility are consistent with high-spin (S = 1) Ni(II), and both molecules exhibit relatively short axial Ni-N bonds and long Ni-N and Ni-S equatorial bonds. At 123 K, the Ni1 complex remains high-spin, but the Ni2 molecule substantially crosses to a structurally distinct diamagnetic (S = 0) state with significant elongation of the axial Ni-N bond and offsetting contraction of the equatorial bonds. The temperature-dependent susceptibility data were fit to a spin equilibrium at Ni2 [ΔH° = 1.13(2) kcal/mol and ΔS° = +7.3(1) cal mol(-1) K(-1)] consistent with weak coupling to lattice effects. Cooling below 100 K results in crossover of the Ni1 complex.
authors: Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United States.
authors: Huaibo
authors: H
authors: Ma
authors: Jeffrey L
authors: JL
authors: Petersen
authors: Victor G
authors: VG
authors: Young
authors: Gordon T
authors: GT
authors: Yee
authors: Michael P
authors: MP
authors: Jensen
mesh_terms: D018360:Crystallography, X-Ray; D008024:Ligands; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*
chemical_list: D008024:Ligands; D009532:Nickel; C017557:nickel subsulfide