IR SPECTRA OF DIMOLYBDENUM TETRA-μ2-PHENYLACETATE COMPLEX AND ITS DERIVATIVES Текст научной статьи по специальности «Химические науки»

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CHEMICAL PROBLEMS 2024 no. 1 (22) ISSN 2221-8688

45

UDC 546.772-057+543.42.061

IR SPECTRA OF DIMOLYBDENUM TETRA-^-PHENYLACETATE COMPLEX AND ITS DERIVATIVES

E.L. Akhmedov, S.Sh. Akberova, K.F. Huseynguliyeva, Sh.Y. Ismayilova

Azerbaijan Medical University S. Vurgun str., 163A, Baku, AZ1022 e-mail: musayeva_saida@mail.ru

Received 26.11.2023 Accepted 23.01.2024

Abstract: The study describes the synthesis, thermal and spectral characteristics of tetra-^2rphenylacetate complex of dimolybdenum - Mo2(O2CCH2CH5)4 and its derivatives in the type [Mo2(O2CCH2CgH5)4]L2' [where L' = a-, fi-picoline (a-, fi-Pic), 4-vinylpyridine (4-VinPy), quinoline (Q). The comparison of IR spectra of the synthesized [Mo2(O2CCH2C(H5)4]L2' complexes with the spectra of liquid L' ligands reveals their great similarity. Nearly every band in the IR spectra of the free L' ligands is reproduced in the spectra of the complex with a slight long-wavelength shift or splitting, which is a consequence of the coordination of L' through the nitrogen heteroatom. However, when comparing the shift values of the stretching vibration frequencies v(ring), non-planar and planar bending vibrations of the C-H and C-C bonds of heterocyclic rings, as well as the values of bending vibrations of the frequencies S(CCC), S(CNC) in the spectra of the [Mo2(O2CCH2C(H5)4]L'2 complexes and the previously obtained [Mo2(O2CH)4]L"2 complex [1] [where, L' and L" = a-, fi-Pic, 4-VinPy, Q], it turns out that the coordination bonds of Mo-L' in axial positions in these adducts are weak. It also revealed that when heating adducts with the composition [Mo2(O2CCH2C(H5)4]L'2, the L' ligands are completely removed at 70-100 oC. After heating of each sample at the appropriate temperature for 2 hours (Table 3), their IR spectra completely coincided with the spectra of the original dimolybdenum tetra-^phenylacetate complex.

Key words: phenylacetate, dimolybdenum, a- and fi-picoline, stretching and bending vibrations, thermolysis DOI: 10.32737/2221-8688-2024-1-45-51

Introduction

As is shown in [1], the complexes like a-hydroxyphenylacetatodimolybdenum [Mo2(O2CCH(OH)C6H5)4]L2 (L is a molecule of an organic base) cannot be synthesized, apparently due to steric hindrances created by the hydroxo group located in the a-position relative to COO group in the mandelic acid

molecule. Replacing the hydroxo group of mandelic acid with a hydrogen atom, for example, in a phenylacetic acid molecule, should eliminate these obstacles. Therefore, in this study, we have carried out the synthesis of complexes of molybdenum (II) with phenylacetic acid.

Materials and methods

Synthesis of tetra-^2-

phenylacetatodimolybdenum

Mo2(O2CCH2C6H5)4. 1 g of phenylacetic acid C6H5CH2COOH is dissolved in 30 ml of distilled water on heating (at about 80 0C). The

and 1.13 g of ammonium nonachlorodimolybdate (II) hydrate (NH4)5Mo2Cl9 • H2O is added in portions. The mixture is stirred for 5 minutes. The resulting light-yellow crystalline substance is filtered off,

resulting solution is cooled to room temperature washed several times with absolute ethyl

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CHEMICAL PROBLEMS 2024 no. 1 (22)

alcohol and dried in vacuum at room Found: Mo-26.8%; C-53.0%; H-4.0%

temperature. The elemental analysis of the Calculated: Mo-26.2%; C-52.4%; H-3.8% sample of the resulting substance is compliant The synthesis given in the method is

with the composition Mo2(O2CCH2C6H5)4. described by the following reaction equation:

(NH4)5M02Cl9 • H2O + 4C6H5CH2COOH = Mo2(O2CCH2C6H5)4 +5NH4Q + 4HCl + H2O

Synthesis of tetra-^2-

phenylacetatodimolybdenum diquinoline

[M02(O2CCH2C6H5)4](C9H7N)2. 0.5 g of tetra-p,2-phenylacetatodimolybdenum in 15-20 ml of quinoline (Q) is heated at about 90 oC in a flask under reflux in a flow of argon until complete dissolution of initial complex. The resulting yellow-brown solution is cooled in an argon atmosphere to room temperature. The precipitated orange-yellow crystals in the form

of quadrangular prisms are filtered, washed with absolute ethyl alcohol and dried in vacuum. Elemental analysis of a sample of the resulting substance corresponds to the composition [M02(O2CCH2C6H5)4](C9HyN)2: Found: Mo-20.0%; C-61.0%; H-4.4%; N-2.9% Calculated: Mo-19.4%; C-60.6%; H-4.2%; N-3.0%

The scheme shows the structure of the synthesized compound:

M

v®

u

I

M

M

u

M

V®

u

I

œ

u

O ^ ^O ""^O^^O

M

Using a similar procedure, derivatives with a-, P-picoline and 4-vinylpyridine were synthesized from Mo2(O2CCH2C6H5)4.

All synthesized compounds

[Mo2(O2CCH2C6H5)4]L2' (L' = Q, a-, P-Pic, 4-VinPy] are diamagnetic, practically insoluble in water and alcohol, and resistant to moisture and

air oxygen.

IR absorption spectra in the region 4004000 cm-1 were recorded on a UR-20 spectrophotometer, in the region 200-500 cm-1 on an IKS-22V spectrometer. Samples were prepared by rubbing the substance with vaseline oil or hexachlorobutadiene.

Results and discussion

In the IR spectrum of crystalline phenylacetic acid, two intense absorption bands with maxima at 1720 and 1420 cm-1 are observed in the region of antisymmetric and symmetric stretching vibrations of the COO group (Table 1, Fig. 1). In coordination of the

acid anion with a molybdenum atom, these frequencies shift to 1510 and 1412 cm-1, respectively, which is typical for carboxylate groups with aligned COO bonds [2]. The absorption bands of the phenyl ring, located in the regions 1610-1580 and 1550-1460 cm-1, do

not practically change their position during the formation of the complex.

The absorption band at 1192 cm-1, observed in the spectrum of Mo2 (O2CCH2C6H5)4, by analogy with [3], we assigned to the stretching vibration of the Ph-C bond.

In the long-wave region of the IR spectrum of Mo2 (O2CCH2C6H5)4, three absorption bands of medium intensity were found at 384, 324 and 290 cm-1 (Fig. 2). The bands at 384 and 324 cm-1, according to [4], are attributed, respectively, to antisymmetric and symmetric stretching vibrations of the Mo-O bond, and the absorption band at 290 cm-1 is presumably to the bending vibration of the MoOO group.

Fig. 1 and 2 present the IR spectra of the complex compounds we synthesized with the composition [Mo2 (O2CCH2C6H5)4]L2' (L'= Q, a-, P-Pic, 4-VinPy], and tables 1 and 2 show some vibrational frequencies observed in these IR spectra.

As is known [5-11], the nature of the coordination of heterocyclic amines can be

judged on the basis of an analysis of the stretching vibrations of the ring, non-planar and planar bending vibrations of the C-H and C-C ring bonds, as well as bending vibrations of CCC- and CNC- groups.

The comparison of the IR spectra of the [Mo2(O2CCH2C6H5)4]L2' complexes (where L' = a-, P-Pic, 4-VinPy, Q) with the spectra of the appropriate liquid ligands shows that almost every absorption band in the spectrum of free ligands is reproduced in the spectrum of the complex with a slight shift or splitting, which is a consequence of the coordination of ligands L' through the nitrogen atom of the pridine ring. At the same time, when comparing the shift of characteristic absorption bands in the spectra of of phenylacetate [Mo2(O2CCH2C6H5)4]L2' and formate [Mo2(O2CH)4]L2'' complexes, it can be noted that in the case of [Mo2(O2CCH2C6H5)4]L2' the changes in the appropriate frequencies are smaller and, therefore, the Mo-N interaction is weaker, than in the case of formate complexes [M02(O2CH)4]L2''.

Table 1. Vibrational frequencies (cm-1) in the IR spectra of phenylacetic acid and dimolybdenum _tetra-^2-phenylacetate and their assignment_

Assignment C6H5CH2COOH Mo2(02CCH2C6H5)4

Ring vibrations 1612, 1582 1610, 1580

Vas (COO) 1720 1510

Sas (CH2^ v(CC)rings 1470, 1440 1462, 1438

Vs (COO) 1420 1412

Ss(CH2), V(CC) rings 1340 1335

v(CC) rings, P(CH) 1298, 1250 1298, 1285

V(Ph-C) 1196 1192

P(CH), p(CH2) 1165, 1080, 1032 1165, 1100, 1085

V(CH2-C) 930 1050, 1038, 952, 93

Y(CC) 870 880

Y(CC), p(CH) 885, 845, 685 850, 772, 703, 675

S(COO) 710 730

S(COC) 607, 615 645, 624

y(ch) 476 482

Vas(MoO) 384

Vs (MoO) 324

S(MoOO) 290

Table 2. Some vibrational frequencies (cm-1) found in the IR spectra of free and coordinated _phenylacetic acid and dimolybdenum complexes and their assignment_

Compound Vas(COO) Vs(COO) AV(COO) Vas(MoO) Vs(MoO) S(MoOO) v(MoN)

C6H5CH2COOH 1720 1420 300

M02(O2CCH2C6Hs)4 1510 1412 98 384 324 290

M02(O2CCH2C6HS)4Q2 1525 1410 115 360 320 305 280

M02(O2CCH2C6H5)4(a-Pic)2 1534 1420 114 370, 368 330 308 273

M02(O2CCH2C6H5)4(P-Pic)2 1530 1408 112 312 320 305 275

M02(O2CCH2C6Hs)4(4-VinPy)2 1532 1404 127 380 332 293 272

4UUU >000 2000 1000 TOO 400

v. cm1

Fig. 1. IR absorption spectra of Mo2(02CCH2C6H5)4 (a), [Mo2(02CCH2C6H5)4]Q2 (b), [Mo2(O2CCH2C6H5)4](4-VinPy)2 (c), [Mo2(O2CCH2C6H5)4](a-Pic)2 (d), [Mo2(O2CCH2C6H5)4](P-Pic)2 (e) in vaseline oil, dotted line - in hexachlorobutadiene.

_i_I_1 1 1-1-1-1—

440 360 280 200 V, cm 1

Fig. 2. Long-wave IR absorption spectra of Mo2(02CCH2C6H5)4 (a), [Mo2(O2CCH2C6H5)4](a-Pic)2 (b), [M02(O2CCH2C6H5)4](P-Pic)2 (c), [Mo2(O2CCH2C6H5)4](4-VinPy)2 (d) in vaseline oil.

Data on thermal stability of phenylacetate [M02(O2CCH2C6H5)4]L2' and formate [Mo2(O2CH)4]L2m complexes are compliant with the results of IR spectroscopy. The behavior of these complexes by heating was studied in the temperature range 25-200 oC in an inert environment (Table 3).

It found that at a temperatures from 70o C to 100o C, complete removal of ligand (L') molecules [Mo2(O2CCH2C6H5)4]L2' occurs. The IR spectra of samples heated to the appropriate temperature (Table 3) and kept in a given mode for 2 hours (2 h.) are completely identical to the IR spectra of the Mo2(O2CCH2C6H5)4 complex.

Table 3. Results of thermal studies of phenylacetate [Mo2(O2CCH2C6H5)4]L2' and formate [Mq2(O2CH)4]L2m complexes [where, L' and L" = a-, P-Pic, 4-VinPy, Q]

Compound Ligand removal temperature, 0C Mass loss (Am) upon removal of the axial ligand, (found/calculated), %

M02(O2CCH2C6H5)4(a-Pic)2 70 20.4/20.2

M02(O2CH)4(a-Pic)2 135 32.6/33.3

M02(O2CCH2C6H5)4Q2 90 26.5/26.0

M02(O2CH)4Q2 158 40.8/40.0

M02(O2CCH2C6H5)4(ß-Pic)2 98 20.9/20.2

M02(O2CH)4(ß-Pic)2 160 33.7/33.3

M02(O2CCH2C6H5)4(4-VinPy)2 100 23.0/22.2

M02(O2CH)4(4-VinPy)2 140 34.4/36.0

The behavior of the complexes by heating is characterized by the following features. Firstly, the removal temperature of L' molecules for tetra-p,2-phenylacetate complexes is 40-60 oC lower than for the appropriate formate derivatives [12]. Secondly, the elimination of ligand L' in them does not cause a significant change in the properties of the complexes: the appearance and light yellow color of the substances are preserved. However, the removal of L'' ligands from tetra-p,2-formate complexes

of dimolybdenum is accompanied by the color change from light yellow to dark green, which is probably the result of the change in the coordination of the formate ligands. Thirdly, for all phenylacetate derivatives, with the exception of the complex with a-Pic, the removal temperature of ligand L' does not depend on their donor ability.

Apparently this is due to additional interactions between the L' axial (a-Pic) and equatorial ligands.

References

1. Golovaneva I.F., Akhmedov E.L., Kotelnikova A.S., Shchelokov R.N. Vicinal optical activity of the binuclear cluster of molybdenum (II) tetra-^-mandalate. Doklady Chemistry. 1985, vol. 284, no, pp. 1147-1150 (In Russian).

2. Zhirnikova E.Yu., Kunavina E.A. IR spectroscopic study of the drug "diclofenac" from various manufacturers. Bulletin of the Orenburg State University. 2015, no. 10 (185), pp. 289-290. (In Russian).

3. Holste G. Darstellung und Eigenschaften einiger Molybdän (n)-Thiocarboxylate. Zeitschrift für anorganische und allgemeine

Chemie. Berlin, 1976, vol.425, no.1, pp. 57-66/

4. Hassan M.B., Wolfgang F. Analysis of the infrared and Raman spectra of phenylacetic acid and mandelic (2-hydroxy-2-phenylacetic) acid. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2011, vol. 78, no.3, pp. 11621167.

5. Gaddam R., Chinnala V., Katla R., Guguloth V., Banoth. N., Guguloth H., Jarupula L.N. Structure Conformation, vibrational properties, NLO activity, HOMO-LUMO and thermodynamic parameters of dinicotinic acid using

experimental and theoretical approach. Biointerface Research in Applied Chemistry. 2022, vol. 12, no. 3, pp. 2752 -2761.

6. David A.T. Metal complexes of pyridine: infrared and raman spectra with particular referece to isotopic labelling studies. Coordination Chemistry Reviews. 1990, vol. 104, no. 2, pp. 251-295

7. Sujata S. Preparation of Cobalt (II) Complexes with Schiff Base 2 (2-hydroxy benzylidine) iminoHydroxamic Acid in the Presence of Bases. Journal of Emerging Technologies and Innovative Research. 2015, vol. 2, №11, p. 2075-2078

8. Gill N.S., Nuttall R.H., Scaife D.E., Sharp D.W.A. The infra-red spectra of pyridine complexes and pyridinium salts. Journal of Inorganic and Nuclear Chemistry. 1961, vol. 18, no. 1, pp. 79-87.

9. Aya E., Kazuya A., Hiromasa T., Shogo K., Yuki M., Kazunari N., Kazunari Y.,Yoshiaki N. Remarkable catalytic activity of dinitrogen-bridged dimolybdenum complexes bearing NHC-

based PCP-pincer ligands toward nitrogen fixation. Nature communications. 2017, vol.8, pp. 1-12. DOI:

10.1038/ncomms14874.

10. Basima M.S., Asia H.A., Rasmia MR. Synthesis and Characterization of Some Mixed Ligand Complexes of Quinaldic Acid and a-Picoline with Some Metal Salts. Al-Mustansiriyah Journal of Science. 2013, vol. 24, no 4, pp. 65-74.

11. Arijit D., Paresh D., Bijaya P., Kartick L.B., Abhijit B., Banti G. Mixed Ligand Complexes of Cobalt (II): Synthesis, Reactivity, Physico-Chemical and Spectroscopic Studies. Asian Journal of Chemistry. 2023, vol. 35, no. 4, pp. 910916.

12. Akhmedov E.L., Kotelnikova A.S., Tsivadze A. Yu., Babievsky I.Z., Abbasov A.M. Synthesis and vibrational spectra of tetra-p-formate complexes of dimolybdenum and its derivatives. Coordination chemistry. 1987, vol. 13, no. 4, pp. 497-506. (In Russian).

TETRA-^tFENÍLASETATODÍMOLÍBDEN KOMPLEKSÍNÍN Va ONUN TÓR9M9L9RÍNÍN ÍQ SPEKTRL9RÍ

E.L. 8hmadov, S.Ç. 8kbarova, K.F. Hüseynquliyeva, Ç.Y. ísmayilova

Azarbaycan Tibb Universiteti Samad Vurgun kûç., 163 A, Baki, AZ1022, e-mail: musayeva_saida@mail.ru

Xülasa: Taqdim olunan maqalada tetra-p2-fenilasetatodimolibden Mo2(O2CCH2C6H5)4 va onun toramalari olan [Mo2(O2CCH2C6H5)4]L2' [L' = a-, P-pikolin (a-, P-Pic), 4-vinilpiridin (4-VinPy), xinolin (Q)] tarkibli klaster birla§malarin sintezi, termiki va spektral xarakteristikalari verilmi§dir. Sintez olunmu§ Mo2(O2CCH2C6H5)4L'- tarkibli komplekslarin va maye halda olan L'-liqandlanrnn ÍQ-spektrlarinin müqayisasi gostarir ki, onlar bir-birina çox ox§ardir. Bela ki, sarbast L' liqandlara maxsus har bir udma zolaqlari onlar asasinda sintez olunmu§ [Mo2(O2CCH2C6H5)4]L2' tarkibli adduktlarin ÍQ-spektrinda müayyan daracada sürü§maya va ya bir neca nazik zolaqlara ayrilmaya maruz qalirlar. Lakin [Mo2(O2CCH2C6H5)4]L2' va avvallar bizim tarafimizdan sintez olunan Mo2(O2CH)4L2'' [1][L' va L'' = a-, P-Pic, 4-VinPy, Q] tarkibli kompleklarin ÍQ spektrlarinin müqayisasi gostarir ki, spektrda [Mo2(O2CCH2C6H5)4]L2' tarkibli adduktlarin da spektrlarinda aksial vaziyyatlarda yerla§mi§ heterotsiklik halqalarin valent raqslarina - v(h3lq3y3) aid udma zolaqlarinin spektrin kiçin dalga uzunlugu tarafa sürü§malari ba§ verir. ÍQ-spektrlarda bundan ba§qa, tsiklik halqalardaki C - H, C - C rabitalarinin müstavi va qeyri-müstavi deformasiya raqslarina uygun udma zolaqlarinin da sürü§masi ba§ verir. Lakin qeyd olunan udma zolaqlarinin

ki9ik dalga uzunlugu tarafa suru§malari ki9ik qiymatlarla saciyyalanir. Bu natica isa onu soylamaya dalalat edir ki, qeyd olunan [Mo2(O2CCH2C6H5)4]L2' tarkibli adduktlarda aksial vaziyyatlardaki Mo - L' koordinativ rabitalar zaifdir. Bundan ba§qa, muayyan edilmi§dir ki, [Mo2(O2CCH2C6H5)4]L2' tarkibli adduktlari qizdirdiqda L'-liqandlarinin tam ayrilmasi 70 -100 oC arasinda ba§ verir va har bir numuna muvafiq temperaturda ~ 2 saat arzinda qizdirildiqdan sonra onun iQ spektri ilkin tetra-p,2-fenilasetatodimolibden kompleksinin spektri ila tam ust-usta du§ur.

A?ar sozlar: fenilasetat, dimolibden, a- va P-pikolin, valent va deformasion raqslar, termoliz

ИК-СПЕКТРЫ КОМПЛЕКСА ТЕТРА-^-ФЕНИЛАЦЕТАТОДИМОЛИБДЕНА

И ЕГО ПРОИЗВОДНЫХ

Э.Л. Ахмедов, С.Ш. Акберова, К.Ф. Гусейнгулиева, Ш.Ю. Исмайлова

Азербайджанский Медицинский Университет ул. Самеда Вургуна, 163A, Baky, AZ1022 e-mail: musayeva_saida@mail.ru

Аннотация: В работе описаны синтез, термические и спектральные характеристики тетра-ц2-фенилацетатного комплекса димолибдена - Mo2(O2CCH2C6H5)4 и его производных типа [Mo2(O2CCH2C6H5)4]L2' [где L' = а-, Р-пиколин (a-, P-Pic), 4-винилпиридин (4-VinPy), хинолин (Q)]. Сравнение ИК-спектров синтезированных комплексов [Мо2(O2CCH2C6H5)4]L2' со спектрами жидких L' лигандов позволяет обнаружить их большое сходство. Почти каждая полоса в ИК-спектре свободных L' лигандов воспроизводится в спектре комплекса с незначительным длинноволновым смещением или расщеплением, что является следствием координации L' через гетероатомом азота. Однако, при сравнении величин смещения частот валентных колебаний У(кольца), неплоских и плоских деформационных колебаний связей С-Н и С-С гетероциклических колец, а также значений деформационных колебаний частот 5(ССС), 5(CNC) в спектре комплексов [Мо2(O2CCH2C6H5)4]L'2, а также полученного нами ранее комплекса [Мо2(O2CH)4]Lм2 [1] [где, L' и L'' = a-, P-Pic, 4-VinPy, Q], можно отметить, что координационные связи Mo-L' в аксиальных положениях в указанных аддуктах слабые. Кроме того, установлено, что при нагревании аддуктов состава [Мо2(O2CCH2C6H5)4]L'2 происходит полное удаление L'-лигандов при 70-100оС. После нагревания каждого образца при соответствующей температуре в течение 2 часов их ИК-спектр полностью совпадал со спектром исходного тетра-ц2-фенилацетатодимолибденового комплекса. Ключевые слова: фенилацетат, димолибден, а- и Р-пиколин, валентные и деформационные колебания, термолиз