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ISSN 0036 0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 9, pp. 1267–1271. .... The average value of six independent experiments was Δs ... Note that it was evident in advance that the quality .... als/pubs/commodity/thallium/mcs 2011 thall.pdf. 5. ... Thermal Constants of Substances, A Handbook, Ed. by.
ISSN 00360236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 9, pp. 1267–1271. © Pleiades Publishing, Ltd., 2012. Original Russian Text © N.N. Kamkin, L.G. Kuz’mina, D.B. Kayumova, N.G. Yaryshev, I.A. Dementiev, A.S. Alikhanyan, 2012, published in Zhurnal Neorganicheskoi Khimii, 2012, Vol. 57, No. 9, pp. 1350–1354.

PHYSICAL METHODS OF INVESTIGATION

Synthesis and Thermodynamic and Structural Characteristics of Thallium(I) Pivalate N. N. Kamkina, L. G. Kuz’minab, D. B. Kayumovab, N. G. Yaryshevb, I. A. Dementieva, and A. S. Alikhanyanb a Moscow b

State Pedagogical University, ul. Malaya Pirogovskaya 1, Moscow, 119882 Russia Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 117907 Russia email: [email protected] Received December 19, 2011

Abstract—Thallium pivalate was first synthesized and studied by mass spectrometry. It was shown that the set of characteristics makes thallium pivalate suitable as a precursor for the CVD preparation of oxide films and oxide materials. DOI: 10.1134/S0036023612090094

Thallium is of interest for its queerness due to which Jean Baptiste Andre Dumas called it a “para doxical” metal [1]. In the chemical properties, thal lium resembles to some extent alkali metals (it is readily oxidized; thallium hydroxide is watersoluble and is a strong base) and to some extend silver (low water solubility of the chloride, bromide, and iodide); however, thallium looks like lead and resembles lead in other physical properties. Moreover, none of the met als forms continuous solid solutions with thallium. Despite these peculiar properties, thallium has not been deeply studied so far, which was due to its low practical value. Thallium and its compounds are used in electronics, in semiconductors, scintillation counters, photoelectric cells and lamps; as catalysts in organic synthesis for selective disproportionation of olefins [2], polymerization and epoxidation [3]. In recent decades, the industrial consumption of thal lium has markedly increased [4]. The consumption of thallium is forecasted to considerably grow if large scale production of wire and films made of thallium HTSC materials with desired flexibility and strength becomes possible. The use of metal βdiketonates for the CVD pro duction of oxide films [5], thermally and corrosion stable optical coatings [6, 7], and HTSC materials [8, 9] at relatively low temperatures stimulated their active research. Less active use of carboxylates is due to the lack of data on their thermal stability and ther modynamic and structural characteristics. Therefore, study of the sublimation behavior of various metal (in particular, thallium) pivalates and determination of the thermodynamic characteristics of vaporization are topical tasks.

The purpose of this work is the synthesis of thal lium(I) pivalate and study of its thermodynamic and structural characteristics. EXPERIMENTAL Thallium(I) pivalate was synthesized by the proce dure we developed, based on heterogeneous interac tion of silver pivalate [Ag(piv)] [10, 11] and the metal (M) whose complex is to be prepared nAg(piv) + M = M(piv)n + nAg. (1) A mixture of silver pivalate and thallium in 5 : 1 mass ratio was charged into a quartz tube (reactor) with a diameter of 12 mm, evacuated to a residual pressure of 1 × 10–2 mmHg, and heated to 130–250°С in a dynamic vacuum. Thallium pivalate formed in reaction (1) was condensed in the cold end of the reac tor. The product yield depended appreciably on the degree of dispersion and homogenization of reactants, being most often 15 to 30% of the amount of metallic thallium. According to chemical analysis, the product composition corresponded to thallium(I) pivalate. Anal. calcd. (%): C, 19.64; H, 2.95. Found (%): C, 18.42; H, 2.72. According to the data of laser mass spectrometry for elemental analysis (EMAL2 instrument), the con tent of the major product was not less than 99.5 wt %. The mass spectral investigations of the thermody namic characteristics of thallium pivalate were per formed on MC1301 and Thermo Fisher Scientific DSQII (TFS) mass spectrometers with a TFS DIP direct injection probe. In the former case, evaporation was performed from molybdenum Knudsen effusion cells with an evaporation to effusion area ratio of ~600, and in the latter case, evaporation occurred from a

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Tlрivgas + e = Tl +gas + + piv igas + 2 e.

Table 1. Mass spectrum of the gas phase above thallium piv alate and the Tl–Ag(piv) system, T = 380 K, Uioniz = 70 V Sample (method)

205Tl+

Tlpiv (TFS) Tlpiv (MS1301) Tl + Ag(piv) (TFS)

100 100 100

TlCO 2+

205

+

205Tlpiv+

C4H 9

0.03 – 0.03

6.7 – 7.0

3.1 3.9 3.0

12 mm long quartz capillary (microcrucible) with an internal diameter of 0.9 mm. Table 1 presents the mass spectra of the gas phase above thallium pivalate recorded using these instruments at 370 K. The same Table presents the mass spectrum of the gas phase above the metallic thallium–silver pivalate system during its evaporation from a quartz capillary directly during the mass spectral experiment. As can be seen from Table 1, the mass spectra in all three experiments are identical. Note that the mass spectral pattern does not allow unambiguous identifi cation of the gas phase composition upon sublimation of the compounds. The composition of the gas phase and the character of vaporization of thallium(I) piv alate were determined in experiments on complete isothermal evaporation of a thallium pivalate sample and ionization of gas phase components. Figure 1 shows ionization efficiency curves (IEC) for the Tl+ ion and the Hg+ ion as the standard. High appearance energy of the Tl+ ion (11.1 ± 0.3 eV) and the absence of ions corresponding to ionization of organic molecules in the mass spectrum of the gas phase (Table 1) attest to the fragment origin of Tl+ ions upon dissociative ionization of only Tlpiv molecules:

(2)

Experiments on full isothermal sublimation of a sample with known weight demonstrated that during the whole evaporation process, the intensities of all ion currents (partial pressure of Tlpiv molecules) in the mass spectrum remained constant, and the complete burningout of the sample in the effusion chamber did not leave any nonvolatile residue. These studies indi cate that sublimation of thallium pivalate is congruent and the saturated vapor above it consists only of mono meric Tlpiv molecules: Tlрivsolid = Tlрivgas.

(3)

Upon investigation of the temperature dependence of the Tl+ ion current intensity in the temperature range of 70–120°С (Fig. 2), the sublimation enthalpy of thallium pivalate was calculated by the Clausius– Clapeyron equation using the leastsquares method. The average value of six independent experiments was Δs H T°(Tlрiv) = 123.6 ± 4.8 kJ/mol. Using the appearance energy of the Tl+ fragment ion from the Tlpiv molecule (11.1 ± 0.3 eV) and the ionization energy of Tl atom (6.1 eV) [12] and using the expres sion D(AB) < Ea(А+) – Еi(А),

(4)

where D(AB) is the dissociation energy of molecule AB; Ea(А+) is the appearance energy of the fragment ion А+ from the molecule AB; Еi(А) is the ionization energy of atom A, the upper limit of the dissociation energy of the thallium pivalate molecule to a thallium atom and a рiv• radical was determined, D00 (Tl–рiv) < 482.5 ± 29 kJ/mol. logIT 6

I, rel. units 2.0 2 1.6 1

5

1.2 4 0.8 3 0.4 2 0 10

2.5 11

12

13 U, eV

Fig. 1. Curves for ionization efficiency of (1) Tl+ and (2) Hg+ at 100°С. The corrected energies are given.

2.6

2.7 2.8 1000/T, K–1

2.9

Fig. 2. Temperature dependence of the Tl+ ionic current efficiency.

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Table 2. Crystal and experimental parameters of the solution and refinement of the thallium pivalate structure Molecular formula

C15H27O6Tl3

Molecular mass Color, habit Crystal size, mm System Space group Unit cell parameters a, Å b, Å c, Å V, Å3 Z ρcalc, mg/m3 μ(MoKα), mm–1 F(000) T, K Radiation (λ, Å) Range of θ, deg Transmission coefficients Tmin/Tmax, absorption corrections Range of reflection indices

916.48 Colorless, block 0.52 × 0.25 × 0.08 Orthorhombic Pbca 14.6080(15) 13.4275(13) 21.813(2) 4278.5(7) 8 2.846 22.566 4278.5(7) 173(2) MoKα (0.71073), graphite monochromator 2.33 ≤ q ≤ 26.00 0.030/0.2654, SADABS –18 ≤ h ≤ 18, –16 ≤ k ≤ 16, –26 ≤ l ≤ 26 34499 4180, Rint = 0.0909 217 1.055 0.0531, 0.1455 0.0676, 0.1520 4.933/–2.680

The number of measured reflections The number of independent reflections The number of refined parameters GOOF on F2 Rfactors for I > 2σ(I) Rfactors for all data Residual electron density (max/min), e Å–3

The resulting dissociation energy points to consid erable ionicity of the metal–ligand bond, which is in line with the high degree of fragmentation of the thal lium complex upon electron impact ionization. The determined dissociation energies and sublimation enthalpies and also the known thallium sublimation enthalpies [13] and the standard formation enthalpy of the рiv• radical [14] were used to estimate the standard formation enthalpies of thallium pivalate in the gas (⎯567.6 kJ/mol) and solid (–691.2 kJ/mol) phases. Xray diffraction experiments. The crystals were crystal debris, most being crystal concretions that can not be indexed on a diffractometer. We were able to index one of the debris, although the Xray diffraction pattern indicated the presence of “excessive” reflec tions caused by its twin nature. The crystal was placed in a CCD SMARTAPEXII diffractometer under a flow of cooled nitrogen, and experimental reflections and the unit cell parameters were measured. RUSSIAN JOURNAL OF INORGANIC CHEMISTRY

The experimental data were first treated using the SAINT program [15]. The structure was solved by the direct method and refined by least squares in the anisotropic approximation for nonhydrogen atoms. The hydrogen atom positions were calculated geomet rically. The positional and thermal parameters of these atoms were refined in the riding model. All calcula tions were carried out by the SHELXTLPlus pro grams [16]. The Xray diffraction experiment and structure solu tion and refinement details are presented in Table 2. Note that it was evident in advance that the quality of the obtained crystals would be insufficient for a high precision experiment, and even the possibility to solve the structure was not obvious. However, we still investi gated these crystals considering that the main task of the study is to determine the compound structure. Vol. 57

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DESCRIPTION OF THE STRUCTURE C(3)

C(5)

The compound is the pivalate of monovalent thal lium [TlPiv]; however, its structural formula is better described as [3(TlPiv)]n. In the crystal, this compound is a onedimensional polymer whose repeating unit is shown in Fig. 3. A fragment of the polymer chain involving only the nearest constants of the metal atom is shown in Fig. 4. All three crystallographically independent pivalate anions perform a chelating bridging function. The piv alate anion, О(1)О(2)С(1)···С(5), is coordinated to Tl(I) by both oxygen atoms. In addition O(1) is also coordinated to Tl(2), while O(2) is coordinated to the thallium atom symmetrically equivalent to Tl(2). Although the Tl(2)···O(1) distance is long, in the spectrum of Tl···O distances in this structure it is still closer to the range comprising the other ionic con tacts (2.53–3.14 Å), whereas the other Tl···O dis tances are longer than 4 Å. The pivalate anion О(3)О(4)С(6)···С(10) performs the chelating func tion towards the Tl(1) atom. The O(4) atom of the anion is also coordinated to Tl(2) and Tl(3), while the O(3) atom is coordinated to the thallium atom sym metrically equivalent to Tl(2). The pivalate anion О(5)О(6)С(11)···С(15) performs a chelating function with respect to Tl(2), and its O(6) atom is also coordi nated to Tl(1), while O(5) is coordinated to Tl(3). All three crystallographically independent thallium atoms have different coordination environments,

O(2) O(5B)

C(2) C(1) C(4) C(8)

O(1) O(3)

Tl(1)

C(6) C(7) Tl(2)

C(9)

O(6)

C(10) O(4)

C(11)

C(13) C(12)

O(3C) O(2A)

C(15) O(5) C(14)

Tl(3)

O(1B)

Fig. 3. Structure of the crystallographically independent fragment of the onedimensional polymer [3(TlPiv)]n. The continuous lines show the closest contacts of Tl atoms and the dashed lines show the contacts of the second coor dination sphere; the letter in the atom number means that this atom is the symmetric equivalent of the atom desig nated without this letter.

C(10A)

O(3A) C(8A)

Tl(1A)

C(6A) C(5A)

C(3A)

O(2B) C(7A) C(9A) C(1A) C(2A)

C(15A)

O(4A) Tl(3A) C(13A) C(12A)

O(1A)

O(6A)

C(11A) C(14A)

O(5A)

C(4A) Tl(2A)

O(2) C(3)

C(5) C(2)

C(1) O(1) O(3)

Tl(1) C(13)

C(4)

O(6) C(12)

C(8) C(7)

C(6) C(10)

O(4) Tl(2)

C(11) C(15) C(14) O(5)

C(9) Tl(3)

O(3C)

O(2A)

Fig. 4. Fragment of the onedimensional polymer taking into account only short contacts of Tl. RUSSIAN JOURNAL OF INORGANIC CHEMISTRY

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Table 3. Coordination environment of Tl atoms (d) Contact

d, Å

Contact

d, Å

Contact

d, Å

Tl(1)···O(1)

2.55(1)

Tl(2)···O(1)

3.31(1)

Tl(3)···O(1B)

2.91(1)

Tl(1)···O(2)

3.14(1)

Tl(2)···O(2A)

2.809(9)

Tl(3)···O(2A)

2.53(1)

Tl(1)···O(3)

2.572(9)

Tl(2)···O(3C)

2.769(9)

Tl(3)···O(4)

2.726(8)

Tl(1)···O(4)

3.02(1)

Tl(2)···O(4)

2.784(8)

Tl(3)···O(5)

2.79(1)

Tl(1)···O(5B)

2.871(9)

Tl(2)···O(5)

2.68(1)

Tl(1)···O(6)

2.99(1)

Tl(2)···O(6)

2.82(1)

which cannot be described in terms of canonical schemes.The coordination contacts of thallium atoms are summarized in Table 3. The Tl(1) and Tl(2) atoms are sixcoordinate and Tl(3) is fourcoordinate. In the CCDC [17], there is no data about the struc tures of thallium pivalates as well as about similar oli gomeric polymers with the formula (TlA)n, where A is an organic acid residue. According to the CCDC, Tl+ also tends to have various coordination numbers and irregular coordination polyhedra. Note in conclusion that the thermodynamic and structural characteristics of thallium(I) pivalate, namely, high volatility, thermodynamic stability, and coordination saturation show that this compound can serve as an excellent precursor for CVD preparation of oxide films and oxide materials. REFERENCES 1. J. B. A. Dumas, J. Pelouze, and H. St. C. Deville, C.R. Acad. Sci. 55, 866 (1862). 2. T. P. Kobylinski and H. E. Swift, J. Catal. 26, 416 (1972). 3. Sivananda Misra and Gangadhar Sahu, J. Macromol. Sci., Pt A: Pure Appl. Chem. 19, 129 (1983). 4. U.S. Geological Survey, Mineral Commodity Summa ries, January 2011, http://minerals.usgs.gov/miner als/pubs/commodity/thallium/mcs2011thall.pdf

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5. L. G. Bloor, C. J. Carmalt, and D. Pugh, Coord. Chem. Rev. 255, 1293 (2011). 6. D. Pugh, L. G. Bloor, S. Sathasivam, et al., Eur. J. Inorg. Chem., No. 12, 1953 (2011). 7. M. Tiitta and L. Niinistou, Chem. Vapor Deposition 3, 167 (1997). 8. G. E. BuonoCore, M. Tejos, J. Lara, et al., Mater. Res. Bull. 34, 2333 (1999). 9. G. V. Bazuev and L. D. Kurbatova, Usp. Khim. 62, 1037 (1993). 10. K. V. Didenko and A. S. Alikhanyan, Proceedings of XVI International Conference on Chemical Thermody namics in Russia (RCCT), Suzdal, 2007, vol. II, p. 4. 11. I. P. Malkerova, A. S. Alikhanyan, N. P. Kuz’mina, and S. P. Paramonov, Zh. Neorg. Khim. 46, 1700 (2001). 12. V. N. Kondrat’ev, Dissociation Energies of Chemical Bonds, Ionization Potentials and Electron Affinity (Nauka, Moscow, 1974). 13. Thermal Constants of Substances, A Handbook, Ed. by V. P. Glushko (Nauka, Moscow, 1971), Iss. V. [in Rus sian]. 14. V. A. Lukyanova, T. S. Papina, K. V. Didenko, and A. S. Alikhanyan, J. Therm. Anal. Calorim. 92, 743 (2008). 15. SAINT, Ver. 6.02A, Bruker AXS, Inc., Madison, Wis consin, USA (2001). 16. SHELXTLPlus, Ver. 5.10, Bruker AXS, Inc., Madi son, Wisconsin, USA (2001). 17. F. H. Allen, Acta Crystallogr., Sect. B 58, 407 (2002).

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