<i>Pseudo</i>-<i>S</i><sub>6</sub> Complex Cations of a Hexakis-<i>N</i>-methylformamide Nickel(II) Complex

Abstract

Nickel(II) complexes are typical good examples for studying any magnetostructural relationship. A slight distortion around the nickel(II) center influences the sign of the zero-field splitting, which will determine the magnetic behavior.1 We previously determined the crystal structures of nickel(II) complexes [Ni(DMF)6](BPh4)2 [hexakis(N,Ndimethylformamide-kO)nickel(II) bis(tetraphenylborate)]2 and [Ni(DMSO)6](BPh4)2 [hexakis(dimethylsulfoxide-kO)nickel(II) bis(tetraphenylborate)],3 where DMF and DMSO represent N,Ndimethylformamide and dimethylsulfoxide, respectively. The [Ni(DMF)6] complex cations were found to take a trigonally compressed pseudo-S6 structure, while the [Ni(DMSO)6] complex cations were found to take both a trigonally compressed pseudo-S6 structure and a pseudo-S4 structure. For the purpose of gaining further examples, in this study, we prepared a niclel(II) complex, [Ni(NMF)6](BPh4)2 [hexakis(Nmethylformamide-kO)cobalt(II) bis(tetraphenylborate)] [NMF = N-methylformamide], and elucidated the crystal structure. The nickel(II) complex [Ni(NMF)6](BPh4)2 was prepared by the addition of a 2-propanol solution (2.0 mL) of sodium tetraphenylborate (~1.1 mmol, 0.37 g) to an NMF solution (1.0 mL) of nickel(II) nitrate hexahydrate (~0.5 mmol, 0.15 g). Slow evaporation of the resulting green solution gave a green single crystal suitable for X-ray analysis. Crystal data are included in Table 1. The structure was solved by direct methods and expanded using Fourier techniques. The non-hydrogen atoms were refined anisotropically, and hydrogen atoms were refined using the riding model. The final cycle of a full-matrix least-squares refinement on F2 was allowed to satisfactory converge with R1 = 0.0460 [I > 2s(I)]. The crystal consists of complex cations, [Ni(NMF)6], and Pseudo-S6 Complex Cations of a Hexakis-N-methylformamide Nickel(II) Complex