Paramagnetic Cobalt(III) Complexes with Organic Ligands. V. The Isolation and Properties of Salts of the Paramagnetic Bis(2,2′-bipyridine)(5-nitrosalicylato)cobalt(III) and of the Paramagnetic “β1 and β2”-Isomers of the 5-Nitrosalicylato(triethylenetetramine)cobalt(III) and Their Derivatives

Abstract

The picrate of the paramagnetic, [Co(5-NO2sal)(bpy)2]2+, has been isolated from a reaction mixture of picric acid, 60% nitric acid, and bis(2,2′-bipyridine)(salicylato)cobalt(III) chloride trihydrate, [Co(sal)(bpy)2]Cl·3H2O, which had been prepared from salicylic acid and cis-bis(2,2′-bipyridine)dichlorocobalt(III) chloride dihydrate. The absorption spectrum and the stability of an aqueous solution of the picrate of the paramagnetic, [Co(5-NO2sal)(bpy)2]2+, were somewhat different from those of complexes of the paramagnetic, [Co(5-NO2sal-R)(NH3)4]2+ (R: H, CH3). Several complexes of the paramagnetic, β1-5-nitrosalicylato-, β2-5-nitrosalicylato-, and β2-3-methyl (and 4-methyl)-5-nitrosalicylato(triethylenetetramine)cobalt(III) have, analogously, been isolated from reaction mixtures of 60% nitric acid and β1-salicylato-, β2-salicylato, or β2-methylsalicylato(triethylenetetramine)cobalt(III) chloride hydrate respectively. Their β1 and β2-isomeric forms were proved by a study of their IR and 1H-NMR spectra. From the IR, NMR, and the magnetic susceptibility measurement results, these compounds are considered to have the paramagnetic complex, [Co(5-NO2sal)L]2+(L: (NH3)4, (en)2, (bpy)2, and trien), and the electron hole is considered to delocalize over the chelate ring containing the cobalt atom and the 5-nitrosalicylato ligand.