First comparative study of the structure of a 1,2-quinone monooxime, its hydrochloride salt and main-group metal complex

Abstract The synthesis of 5-ethylamino-4-methyl-1,2-benzoquinone-2-oxime (5-EtagoH), its hydrochloride salt (5-EtaqoH 2 + Cl − · H 2 O) and potassium complex K9%-Etaqo)(5-EtaqoH) · 2H 2 0 are described. The X-ray crystal structure of all three compounds are also reported. The neutral 5-EtagoH was found to show largely quinone oxime rather than nitrosophenol character. The hydrochloride salt had essentially a 2,5-oxime imino structure with the acidic proton attached to the quinonoid carbonyl oxygen. The potassium atom in the complex K(5-Etaqo)(5-EtaqoH) · 2H 2 O is coordinated to one neutral and one ionic ligand via the oxime nitrogens and the quinonoid carbonyl oxygen forming a five-membered chelate ring. The metal is therefore coordinated to seven donor atoms and is in a distorted pentagonal bipyramidal environment.