The dissertation is dedicated to the development of a new approach to the synthesis of multinuclear copper compounds, which consists in oxidative dissolution of copper powder in the presence of copper(II) halides in non-aqueous solution of organic ligands on air.
The difference of the proposed approach from the widely used direct synthesis with ammonium salts is the use of copper(II) halides, which simultaneously act as a controlled source of anions and a primary oxidant of metallic copper.
The interactions in reaction systems Cu – CuX2 – L1 – Solv – O2, Cu – CuX2 – L1 – L2 – Solv – O2, where CuX2 – CuCl2, CuBr2, CuCl2·2H2O, L1 – pyrazole ligand (3,5-dimethyl-1H-pyrazole, 1H-pyrazole, 4-iodo-1H-pyrazole), L2 – aminoalcohol ligand (diethanolamine, triethanolamine), Solv – CH3CN, CH3OH, DMF were studied. The optimal conditions for the synthesis of copper(II) pyrazolate complexes and mixed ligand copper(II) complexes with pyrazoles and aminoalcohols were selected. It was shown that the optimal molar ratio between reagents for the synthesis of µ3-oxocentric trinuclear copper(II) pyrazolate complexes is 1:1:2 (copper:copper(II) halide:pyrazole ligand). The final products are formed after the stage of formation of known trinuclear copper(I) compounds. The formation of mainly tetranuclear compounds [Cu4(µ4-O)(µ2-X)6(L1)4] (X – Cl, Br; L1 – 3,5-dimethyl-1Н-pyrazole, 1Н-pyrazole) occurs when the molar ratio is changed to 1:2:3. Partial bromination of 3,5-dimethylpyrazole molecules in 4th position (К3 and К4) occurs in systems with copper(II) bromide due to the formation of a small amount of free bromine during the oxidation of trinuclear copper(I) complexes. A scheme of this process is proposed. 10 New copper(II) pyrazole-containing complexes have been synthesized and characterized, 8 of them are exclusively pyrazolate, and 2 mixed ligand compounds with pyrazole and aminoalcohol ligands. It was noted that in most systems mainly known mononuclear complexes are simultaneously formed with multinuclear compounds. A new mononuclear coordination compound [Cu(Hpz)2Cl2] (К1) is formed using 1H-pyrazole in the 1Cu – 1CuCl2 – 2Hpz system. The multinuclear µn-oxocentric pyrazolate complex К8 forms a multinuclear multiligand compound with new topology (К9) in interaction with aminoalcohols. A similar multinuclear complex К10 is formed by interaction of materials in the system Cu0 + Cu2+ + L1 + L2 + Solv. For the first time, two similar structures of mixed ligand copper(II) pyrazolate aminoalcohol coordination compounds (К9 and К10) were obtained by two fundamentally different techniques: due to the interaction of a metallic copper powder and the corresponding copper(II) halide in the presence of two ligands (pyrazole and aminoalcohol – К10), as well as a result of direct interaction of the pre-synthesized pyrazole-containing complex with aminoalcohol (К9). К3 and К4 include uncoordinated chloroform molecules, К10 contains uncoordinated water molecules. Most of the first synthesized coordination compounds have a molecular structure (except for К10 – ionic structure) and consist of neutral particles. X-ray powder diffraction confirms the crystalline nature of some analyzed samples (К5–К8) and the formation of individual compounds. Thermogravimetric analysis of К5 and К6 showed that this compounds
are stable to a temperature of 100 ˚С. There was no effect of chloroform solvent on the formation of К4 structure, because the results of elemental analysis of the powder sample obtained from methanol solution were identical to the results of elemental analysis of К4 single crystals isolated after dissolution of the initial powder in chloroform with subsequent crystallization of the product. It is shown that the ability of pyrazolate complexes to form polymorphic modifications (К8) depends on the conditions of synthesis and crystallization. The influence of the substituent's volume (Iodine) in the pyrazole ring on the formation of a nine-membered trinuclear structure was studied. It is shown that the copper atoms in К5 and К6 form a planar 9-azaMC-3 structure Cu3(μ-Ipz)3, centered by a hydroxy group in which the oxygen atom is noticeably inclined from the plane of the 9-membered metallacycle. In the case of use of CuCl2, polymer comprising from dimeric fragments, in which the coordination number of one of the copper atoms is complemented to 5 due to solvent molecule coordination, is formed. In the system Cu – CuBr2 – IpzH polymeric structure is formed as well, in which geometric environment of one of the copper atoms is completed due to linkage of structural fragments by the bromine bridging atoms.
The formation of such specific structure of the polymeric complexes can be particularly explained by smaller ionic radius of chlorine as compare to bromine anion. The developed preparative procedure can be used for the synthesis of similar trinuclear substituted pyrazole structures.
