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)]center dot 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)]center dot 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.