Cation-Induced Structural Diversity in the Cobalt(II)/Nitranilato System: 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.