The nickel complex nBu4N[Ni(-tpdt)2] (2) (-tpdt = 2,3-thiophenedithiolate) has been prepared and characterized. A salt of this monoanionic paramagnetic complex, [Fe(Cp*)2][Ni(-tpdt)2] (3), was obtained with decamethylferrocene, crystallizing in the monoclinic space group P21/a with a = 15.443(3), b = 10.237(1), c = 20.360(2) Å, β = 107.54(1)°, V = 3069.1(7) Å3, Z = 4. Its structure consists of alternating cationic and anionic layers, with short interlayer contacts defining alternating cation−anion chains. Magnetic characterization of 3 at low applied magnetic fields revealed an antiferromagnetic transition at TN = 2.56 K. Below TN, 3 displays a metamagnetic behaviour with a critical field of 0.07 T at 1.6 K. The magnetic properties of this compound are compared with those of the analogous salts with diamagnetic gold dithiolate [Fe(Cp*)2][Au(-tpdt)2] (4), and diamagnetic decamethylcobaltocenium, [Co(Cp*)2][Ni(-tpdt)2] (5), which are also reported. This comparison shows that the ferromagnetic interactions observed in 3 are due to cation−anion intrachain interactions.