Cation-Induced StructuralDiversity in the Cobalt(II)/NitranilatoSystem: A Monomer, a Dimer, a Trimer and a Chain

Herein, we show how it is possible to prepare a monomer, a dimer, a trimer and a chain with cobalt­(II) and the ligand nitranilato (3,6-dinitro-2,5-dihydroxy-1,4-benzoquinone dianion = C₆O₄(NO₂)₂^2– = NA^2–) by simply changing the counter-cations. Thus, we show that when we combine the ligand NA^2– with cobalt­(II) in the presence of a bulky cation as PPh₄⁺, we obtain compound (PPh₄)₄[Co­(NA)₃] (<b>1</b>), which contains the first monomeric anion of the type [Co­(L)₃]^4– (L = any anilato ligand). With a smaller cation as NMe₄⁺, we obtain (NMe₄)₂[Co₂(NA)₃(H₂O)₄] (<b>2</b>), a rare example of anilato-containing dimer based on a transition metal (TM). With a larger cation as NPr₄⁺, we obtain a trinuclear cobalt–nitranilato complex formulated as (NPr₄)₂[Co₃(NA)₄(H₂O)₆] (<b>3</b>) and finally, when using the small NH₄⁺ cation, we obtain the neutral chain: [Co­(NA)­(H₂O)₂] (<b>4</b>). This work presents the synthesis and structure of these compounds and the magnetic characterization of compounds <b>2</b>–<b>4</b> that show the presence of very weak antiferromagnetic interactions between the cobalt centers through the anilato bridges.