Coordination compounds of copper(II), nickel(II), and cobalt(II) with β-thiosemicarbazones of isatin and N-methylisatin

Abstract

Isatin thiosemicarbazone (HL) reacts in aquoeus-ethanolic medium with copper(II) chloride and bromide (pH 7–7.5, ethanolic KOH) to give coordination compounds CuLX⋅nH₂O (X = Cl, Br; n = 3, 4). In the presence of amines (A = C₅H₅N, 3-CH₃C₅H₄N, and 4-CH₃C₅H₄N), complexes CuALX⋅2H₂O and CuA₂LX⋅H₂O (X = Cl, Br) are formed. With nickel(II) or cobalt(II) chlorides, thiosemicarbazone HL, and pyridine (1:1:3) as starting compounds, compounds MPy₂LCl⋅H₂O (M = Ni, Co) are isolated. Under similar conditions, N-methylisatin β-thiosemicarbazone (HL’) reacts with chlorides of the above-noted metals in the presence of pyridine to give complexes MPy₂L’Cl⋅H₂O (M = Cu, Ni, Co). All the complexes are monomeric and have a pseudooctahedral structure of the coordination unit. Thiosemicarbazones HL and HL′ in these complexes behave as tridentate monodeprotonated O,N,S-ligands. Thermolysis of these substances passes through the stages of dehydration (60–90°C), deaquation (135–140°C) or deamination (160–215°C), and complete thermal decomposition (560–670°C).