Gilroy, Joe B. Otieno, Peter O. Ferguson, Michael J. McDonald, Robert Hicks, Robin G. Synthesis and Characterization of 3-Cyano- and 3-Nitroformazans, Nitrogen-Rich Analogues of β-Diketimine Ligands The synthesis and characterization of several formazans containing strong electron-withdrawing substituents (cyano and nitro) in the 3 position of the ligand backbone are described. Reactions of aryldiazonium cations with the conjugated bases of either cyanoacetic acid or nitromethane lead to 1,5-diaryl-3-cyano- or 3-nitroformazans, respectively. When these reactions are carried out in aqueous conditions, the range of aromatic groups is limited by the stability of the diazonium salt. However, 3-nitroformazans containing bulky substituents on the nitrogen atoms (2,6-dimethylphenyl, 2,4,6-trimetyhlphenyl, 2,6-diisopropylphenyl, and 3,5-ditert-butylphenyl) could be made by performing the reactions under nonaqueous and anhydrous conditions. NMR and electronic spectroscopic studies indicate that the 3-nitroformazans exist exclusively as closed (<i>trans-syn, s-cis</i>) isomers whereas the 3-cyanoformazans exist as mixtures of isomers which are substrate-dependent. The crystal structures of five of the formazans are presented: two 3-nitroformazans, both of which are closed, and three 3-cyanoformazans, two of which are closed and one of which adopts an open (<i>trans-syn</i>, <i>s-trans</i>) structure. Solid state (diffuse reflectance) spectroscopy has been employed to ascertain the isomeric preferences of the other formazans which could not be crystallographically characterized. nitroformazan;substituent;spectroscopic studies;Solid state;isomeric preferences;cyanoacetic acid;cyanoformazan;formazan;ligand backbone;aryldiazonium cations;NMR;diazonium salt;crystal structures;isomers;3 position 2008-02-18
    https://acs.figshare.com/articles/dataset/Synthesis_and_Characterization_of_3_Cyano_and_3_Nitroformazans_Nitrogen_Rich_Analogues_of_Diketimine_Ligands/2956648
10.1021/ic7019445.s003