Field-Induced Slow Magnetic Relaxation in the Ni(I) Complexes [NiCl(PPh3)2]·C4H8O and [Ni(N(SiMe3)2)(PPh3)2]

Direct current (dc) and alternating current (ac) magnetic measurements have been performed on the three Ni­(I) complexes: [NiCl­(PPh3)3], [NiCl­(PPh3)2]·C4H8O, and [Ni­(N­(SiMe3)2)­(PPh3)2]. Fits of the dc magnetic data suggest an almost similar behavior of the three compounds, which display only moderate deviations from the spin-only values. The ac magnetic investigations reveal that the two complexes with trigonal planar coordination[NiCl­(PPh3)2]·C4H8O and [Ni­(N­(SiMe3)2)­(PPh3)2]display slow magnetic relaxation at low temperatures under applied dc fields, whereas tetrahedral [NiCl­(PPh3)3] does not. Ground and excited states as well as magnetic data were calculated by ab initio wave function based multi-configurational methods, including dynamic correlation as well as spin–orbit coupling. The two trigonal planar complexes comprise well-isolated S = 1/2 ground states, whereas two S = 1/2 states with a splitting of less than 100 cm–1 were found in the tetrahedral compound.