Ferromagnets based on polymeric 2,3,6,7‐tetrachloronaphthalene‐1,4,5,8‐tetrathiolato nickel and cobalt complexes

The polymeric nickel complexes 3, 5, 7, 8 and cobalt complexes 4, 6 were synthesized from the bis (tetrabutylammonium) 2,3,6,7-tetrachloronaphthalene-1,5-dithiol-4,6-dithiolate (2) or the tetrathiolate 1 and the corresponding metal-ions (Ni2+ and Co2+), using a large excess of tetrabutylammonium bromide for introducing NBu4+ as counter ion. The diamagnetic nickel coordination polymer 3 was oxidized by iodine to the paramagnetic complex 5. By exchange of the NBu4+ ion by Ni2+ and the tetrathiafulvalenium ion, respectively, the complexes 7 and 8 are obtained. The coordination polymer 7 was characterized as ferromagnetic beneath 20 K by investigating the temperature dependence of the magnetic susceptibility and the magnetization behavior. A coercive field of 1200 Oe was determined from the hysteresis loop of 7 at 4.4 K. The measured heat capacity of 7 in dependence on the temperature is in good accordance with a ferromagnetic spin ordering below 20 K. Magnetic properties comparable with those of 7 were determined for the complexes 4 and 8.