Spectroscopic and electrochemical properties of nickel(II),iron(III) and cobalt(II) complexes with benzilbisthiosemicarbazoneimportance of working conditions and the metal salt used in the final complex

摘要

Reactions of benzilbisthiosemicarbazone (LH6) with nickel, cobalt arid iros ~hbilde mini nilmte piie different complexes depending on the salts used and the working conditions. Reactions from nic*d eMutik gut three complexes. 1. 2 and 3 when the solvent or the pH is modified. Complex I is obtained in ethanol under reflux. and m~rsoI. independently of temperature and also with basic medium. Complex 2 is formed by working in ethanol as room uawaahint The Iipnd acts as a dianion in both complexes. In the presence of hydrochloric acid, the new isolated complex 3 ~ the uual form of the ligand. Reaction from nitrate yields only complex 1. Reactions with iron chloride give two new couipkzes sib different formulae and grade of deprotonation in the ligand. For complex 4, obtained at room temperature. L14 ~8 as — mis with a ligand—iron ratio of 2:1 and in its neutral form with a 1:1 ratio in complex 5, working under reflux. Reactions wib iu~ niuare yield complex 6, with the ligand in an intermediate situation, as anion but a nitrate remains. Complexes 7 and U. viii. 1:1 cobek—ligand molar ratio are isolated from reactions with cobalt nitrate; both contain nitrate and ethanol or namer we ciounpiete the co-ordination sphere. Attempts to get a macrocyclic thiosemicarbazone from reaction of benail and LIII in the J*aeace of nickel or iron salt gave the complexes obtained, in absence of the dicarbonyl molecule. Electrochemical beba~iour of couuplexes studied by cyclic voltammetry show metal-centred reduction processes for all of them. The reductionoxidatien w~mznd values depend on the structures of complexes. Nickel complexes exhibit waves corresponding to Ni(IJl)—Ni(lI) prorms. Eintradwmical response of iron complexes depends on the presence of chloride ions.