Synthesis and Characterization of Ni(II) Complexes

To a DCM solution of NCBrS2 (30 mg, 0.087 mmol), a suspension of Ni(COD)₂ (24 mg, 0.087 mmol) was added. The mixture was stirred at room temperature for 5 min. The solution was filtered through celite to remove Ni black. The desired product was crashed out as a reddish brown powder by adding an excess amount of Et₂O. Yield: 13 mg, 54%. X-ray quality crystals of [(NCS2)Ni(μ-Br)]₂ were obtained by slow diffusion of Et₂O diffusion into a dichloromethane solution at ‒35 °C
UV–vis (DCM; λ nm (ε, M⁻¹ cm⁻¹)): 335, 470 nm.
Elemental Analysis: found, C 41.35%, H 3.15%, N 3.19%; calculated C₃₀H₂₈Br₂N₂Ni₂S₄·CH₂Cl₂, C 41.06, H 3.33, N 3.09%.
MALDI-TOF MS (m/z): 820.8760; calcd. for [(NCS2)Ni(µ-Br)]₂ + H⁺, C₃₀H₂₈Br₂N₂Ni₂S₄: 820.8267.
To a DCM solution of [(NCS2)Ni(µ-Br)]₂, TlPF₆ was added in a MeCN solution. The color changes from red to yellow-brown. It was stirred for two hours, and the solution was filtered through a syringe filter to separate the TlBr. The dark brown solution was reduced in volume and a brown powder was crashed out by adding excess diethyl ether. Despite several attempts using different counterions, no crystal of 2 could be grown. But it was characterized by IR, ESI-MS, EA, and UV–vis. A solution magnetic moment of 2.68 μ_B, corresponding to two unpaired electrons is suggestive of an octahedral geometry in solution.
IR (ν_CN): 2331, 2303 cm⁻¹UV–vis (MeCN; λ nm (ε, M⁻¹ cm⁻¹)): 273 (280), 308 (60)
ESI-MS (m/z): 518.9871; calcd for [(NCS2)Ni(MeCN)(OTf)]-H, C₁₈H₁₆F₃N₂NiO₃S₃: m/z 518.9629.
Evan’s Method: µ_eff = 2.68 µ_BWhen attempting to recrystallize 2 out of a MeCN/Et₂O solution, we often found crystals of [(NCHS2)Tl][PF₆], which points towards the proclivity of the soft thioether ligands to coordinate to the soft Tl⁺.
Elemental Analysis: found, C 38.38%, H 3.38%, N 6.46%; calculated C19H20F6N3NiPS2·0.1 TlPF₆, C 38.48, H 3.40, N 7.08%.