Synthesis and properties of the complexes of 1,3-diphenyltriazenes of lanthanum, manganese and cobalt

Complex compounds of 1,3-diphenyltriazenes of lanthanum, manganese and cobalt have been synthesized. The composition and structure of the complexes were studied by IR, electron spectroscopy, chemical, X-ray and thermogravimetric analyses. In accordance with the data of elemental analysis and thermogravimetry in the complexes of lanthanum, cobalt and manganese, the ratio of metal:ligand is 1:3, 1:2 and their composition is defined by the formulas LaL _3, MnL ₂ и CoL ₂ . The catalytic activity of obtained complexes in the reaction of liquid-phase oxidation of petroleum hydrocarbons was studied.

Keywords: diphenyl triazene, complex, lanthanum, manganese, cobalt thermal stability

Triazenes are a class of compounds based on the charac-teristic functional group of three catenated nitrogen atoms, R–N=N–N(H)–R, which exhibit a remarkable broad variety of properties and uses. They have gained application as antitumor drugs (dacarbazine, temozolomide), as blocks in different kinds of organic synthese like the cyclisation of ethynylphenyl-triazenes to indazole and cinnoline heterocycles. 1,3-di-substituted triazene are N–H acidic. Strong bases allow for the deprotonationto the triazenide(1–) ions, which are versatile ligands towardall kinds of metal ions [1–5].

In the presented work, we have discussed the results of the researches on synthesis of the complexes of lanthanum, manganese and cobalt with 1,3-diaryltriazenes (La-Tr, Mn-Tr and Cr-Tr), and studied the catalytic activity of obtained complexes in the reaction of liquid-phase oxidation of naphtheneparaffinic hydrocarbons isolated from diesel fraction of Azerbaijan petroleum.

In accordance with the data of elemental analysis and thermogravimetry in the complexes of lanthanum, cobalt and manganese, the ratio of metal:ligand is 1:3 1:2, and their composition is defined by the formulas LaL _3, MnL ₂ и CoL ₂ .

In IR spectra of the complexes, the absorption bands at 3200 cm ^-1 which is characteristic for stretching vibrations of aminogroup disappears and this shows that aminogroup participates in a complexation in deprotonated form. Noticeable changes in frequency and intensity of the N-N and N=N vibrations under the complexation are observed. The absorption band for CoL ₂ complex at 1200 cm ^-1 (N-N vibration) in ligand practically disappears, and the absorption band at 1240 cm-1 shifted towards high wave number and appears at 1280 cm ^-1 . The N-N absorption band (in initial ligand at 1440 cm ^-1 ) under the complexation also undergo the shift towards high frequencies and is observed at 1480 cm ^-1 .

In electronic absorption spectra in both complexes, a charge transfer band are observed at 390 nm of MnL ₂ and 430 nm of CoL ₂ , also low-intensity absorption at 560 cm ^-1 for the last complex.

In electronic absorption spectra in both complexes, a charge transfer band are observed at 390 nm of MnL ₂ and 430 nm of CoL ₂ , also low-intensity absorption at 560 cm ^-1 for the last complex.

We conducted thermogravimetric analysis for determination of the composition and thermal stability of the investigated complexes. The results of the thermogravimetric investigations showed that the process of decomposition of cobalt complex occurs in two stages(Fig.1). In the first stage at temperature of 185–1950С occurs the loss of weight of 57 %, in the second stage — 17 % (temperature of 340–460 ⁰ С). Unusually low decomposition temperature of ≈190 ⁰ С and its narrow range of 185–195 ⁰ С are associated with the decomposition

Fig.1. Thermogram of cobalt(II) complex with 1,3-diphenyltriazenes

Fig.2. Thermogram manganese(II) complex with 1,3-diphenyltriazenes

of the ligand by relatively weak N-N bonds. Also the catalytic effect of ions of cobalt on ligand decomposition is possible. The role of the metal in the decomposition of the complex is confirmed in case of thermal decomposition of manganese compound which decomposed in three stages. However, temperatures of the beginning of decomposition stages and their ranges significantly vary. For the manganese temperature in the first stage the weight loss at temperature range of 80–225 ⁰ С is 32 %, in the second stage (temperature of 240–750 ⁰ С) the weight loss is 38 %, in the third stage (800–1000 ⁰ С) the weight loss constitutes 14 %(Fig.2).

Thermal decay for the lanthanum complex occurs in three stages(Fig.3). For the lanthanum temperature in the first stage the weight loss at temperature range of 80–240 ⁰ С is 23 %, in the second stage (temperature of 240–500 ⁰ С) the weight loss is 15 %, in the third stage (500–1000 ⁰ С) the weight loss constitutes 17 %.

Fig.3. Thermogram of lanthanum complex with 1,3-diphenyltriazenes

In the next stage, the catalytic activity of synthesized complexes in the process of oxidation of naphthene-paraffinic hydrocarbons separated from diesel fraction was studied. A diesel fraction of 185–329 ⁰ С separated from Azerbaijan petroleum which previously dearomatized with sulfuric acid of 98 % was used as a raw material [6]. A mixture of naphtheneparaffinic hydrocarbons obtained after dearomatization, was oxidized with atmospheric oxygen in the liquid phase in the presence of Mn-Tr and Cо-Tr used as the catalyst. The oxidation process were conducted at temperature of 135–140°С in the bubble-type reactor at air consumption of 300 l/h. for 5 h.

1. Beck J., Hörner M., Dittmann G. A Macrocyclic Bistriazene and its Complexes with Divalent Metal Ions. Journal of Eur. J. Inorg. Chem., 2009, pp.4314–4319, doi:10.1002/ejic.200900470
2. Su-Ping Luo, Jia-Mei Lei, Shu-Zhong Zhan. Synthesis, characterization, luminescent, and catalytic performance of a dinuclear triazenido-silver complex. Journal of Coordination Chemistry, 2018, 71(8), pp.1–19, doi: 10.1080/00958972.2018.1457788
3. Juan José Nuricumbo-Escoba Carlos Campos-Alvarado Gustavo Ríos-Moreno David Morales-Morales Patrick J. Walsh Miguel Parra-Hake. Binuclear Palladium(I) and Palladium(II) Complexes of ortho-Functionalized 1,3-Bis(aryl)triazenido Ligands. Inorganic Chemistry Journal, 2007, 46, 15, pp.6182–6189
4. Xue. D., Luo, S.-P.Chen, Y.-Y., Zhang. Z.-X., Zhan. S.-Z. Synthesis, characterization and electrocatalytic properties of a tetranuclear triazenido-copper(I) complex. Journal of Polyhedron, 2017, 132, pp.105–111, doi:10.1016/j.poly.2017.04.035
5. Vajs J., Steiner I., Brozovic A., et al. The 1,3-diaryltriazenido(p-cymene)ruthenium(II) complexes with a high in vitro anticancer activity. Journal of Inorganic Biochemistry, 2015, Vol.153, pp.42–48
6. Afandiyeva L. M., İbragimov Kh.J., Rustamli G.Yu., et al. Catalytic oxidation of naphthene-paraffin fraction by air oxygen in the presence of γ-Al ₂ O ₃ modified by salts Cr, Co-, Mn. Chemical Problems Journal, 2019, № 2 (17), pp. 323–329