The thermodynamic properties of rare-earth metal binuclear acetates and pivalates

323

ISSN 0036-0244, Russian Journal of Physical Chemistry, 2006, Vol. 80, No. 3, pp. 323–329. © Pleiades Publishing, Inc., 2006.Original Russian Text © Zh.V. Dobrokhotova, I.G. Fomina, M.A. Kiskin, M.A. Bykov, G.V. Belov, V.M. Novotortsev, 2006, published in Zhurnal Fizicheskoi Khimii, 2006, Vol. 80,No. 3, pp. 400–407.

INTRODUCTION

Rare-earth metal complexes are known as promisingmolecular precursors for the preparation of diversematerials, for instance, superconductors, magnets, cat-alysts, and luminophors [1–4]. In this respect, mono-and polynuclear metal carboxylates hold a special posi-tion among the

f

-element complexes. These compoundsattract attention because of comparative ease of remov-ing carboxylate ligands by solid-state thermolysis. It isalso believed that these compounds are characterizedby comparatively high volatility [5, 6]. They thereforeoffer much promise for use as molecular precursors inthe preparation of metal oxides.

Thermodynamic analysis data on decompositionprocesses can be used to effectively predict the pathsfor synthesizing inorganic materials from complexes.In many instances, this allows us to obviate the neces-sity of performing fairly laborious and expensive exper-iments. Correct thermodynamic calculations requireknowledge of the thermodynamic characteristics of for-mation of compounds under consideration.

The purpose of this work was to determine the ther-modynamic properties of binuclear La, Sm, Eu, and Tmacetates and La, Sm, and Eu pivalates using experimen-tal and calculation methods of thermodynamics.

EXPERIMENTAL

In [7], we studied approaches to the synthesis ofsome lanthanide (La, Sm, Eu, and Tm) binuclear ace-tates and pivalates, their structures, magnetic proper-ties, and thermal decomposition routes in the solidphase in an inert atmosphere.

The objects of study in this work were structurallycharacterized binuclear acetates

å

2

(

η

1

,

η

2

–ééëëç

3

)

2

(

η

2

–ééëëç

3

)

4

(ç

2

é)

4

·

x

ç

2

é

(M = La

(

1

),

Sm

(

2

),

Eu

(

3

),

and Tm

(

4

)

), in which twometal atoms have coordination number 9 and are linkedwith each other by two tridentate chelate-bridge acetatogroups, and pivalates

å

2

(

µ

2

–

OOCCMe

3

)

4

(

OOCCMe

3

)

2

(ç

OOCCMe

3

)

4

·

ç

OOCCMe

3

(M = La

(

5

),

Sm

(

6

),

and Eu

(

7

)

), in which two metalatoms have coordination number 8 and are linked witheach other by four bridge trimethylacetato groups. Thestructure of binuclear rare-earth metal (a) acetates and(b) pivalates is shown below:

The Thermodynamic Properties of Rare-Earth Metal Binuclear Acetates and Pivalates

Zh. V. Dobrokhotova

1

, I. G. Fomina

1

, M. A. Kiskin

1

, M. A. Bykov

2

, G. V. Belov

2

, and V. M. Novotortsev

1

1

Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,Leninskii pr. 31, Moscow, 117907 Russia

2

Faculty of Chemistry, Moscow State University, Leninskie gory, Moscow, 119899 RussiaE-mail: [email protected]

Received March 4, 2005

Abstract

—The temperature dependence of the heat capacities of binuclear acetates

å

2

(

η

1

,

η

2

–ééëëç

3

)

2

(

η

2

–ééëëç

3

)

4

(ç

2

é)

4

·

x

ç

2

é

(M = La

(

1

),

Sm

(

2

),

Eu

(

3

),

and Tm

(

4

)

) (113–330 K); pivalates

å

2

(

µ

2

−

OOCCMe

3

)

4

(

OOCCMe

3

)

2

(ç

OOCCMe

3

)

4

·

ç

OOCCMe

3

(M = La

(

5

),

Sm

(

6

),

and Eu

(

7

)

) (113–320 K);and intermediate products of their thermal decomposition

å

2

(ééëëç

3

)

6

(113–330 K) and M

2

(

OO

ëë

Me

3

)

6

(113–500 K) and enthalpy changes at particular decomposition stages were determined by differential scanningcalorimetry. The composition of the solid phase formed in decomposition was determined experimentally. Thecomplete set of thermodynamic data was obtained, including

C

p

(

T

),

S

°(298),

∆

f

H

°(298)

, and

∆

f

G

°(298)

, forbinuclear lanthanide acetates and pivalates specified above. The composition of the gas phase formed in decom-position was determined, which allowed us to suggest a resultant scheme of the thermal destruction of pivalates.The reliability of this scheme was demonstrated.

DOI:

10.1134/S0036024406030034

CHEMICAL THERMODYNAMICS AND THERMOCHEMISTRY

324

RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY

Vol. 80

No. 3

2006

DOBROKHOTOVA

et al

.

The temperature dependences of the heat capacitiesof the initial compounds and intermediate products of

OM

O

H2OO

O

OH2 O

O

OM

O

OH2

OO

H2OO

O

(‡)

O

MO

O

CMe3

CMe3

OHO OH

CMe3OOH

Me3C

O

CMe3

OO

O

CMe3

O

MO

HO

CMe3

CMe3

HOOHO

Me3C OO

CMe3

O

CMe3

O O

O

CMe3

(b)

their decomposition (å2(ééëëç3)6 (anhydrous ace-tates) and M2(OOëëMe3)6 (tris-pivalates)) weredetermined by differential scanning calorimetry on aDSC-30 module of a TA-4000 thermoanalyzer (Met-tler) over the temperature ranges 113–330 (acetates andanhydrous acetates), 113–320 (pivalates), and 113–500 K (tris-pivalates) (Tables 1–4).

Heat capacities were measured on the thermoana-lyzer in two stages. First, the base DTA curve wasrecorded during heating of two empty containers ofsimilar masses. The deviation of the base line from zerowas caused by the difference of the heat capacities ofthe containers and the elements of the sensor itself. Thesecond stage included measurements with the samplesto be studied. Heat capacity calculations (taking intoaccount base experiment data) were performed using aPC-11 processor and the program provided by the man-ufacturer of the thermoanalyzer.

The substances to be studied were placed intoexpendable aluminum containers of volume 40 µl andsealed off using a special device. Close thermal contactbetween the sample and thermocouple was attained byevenly distributing the substance over the bottom of thecontainer. In a single experiment, fairly small samples

Table 1. Temperature dependences of the heat capacity (Cp(±2%), J/(mol K)) of metal acetates M2(η1, η2-OOCCH3)2 ·(η2-OOCCH3)4(H2O)4 · H2O (M = La (1), Sm (2), Eu (3),and Tm (4))

T, K1 2 3 4

x = 0.5 x = 4

113 345.3 438.0 451.1 446.2120 372.5 463.6 474.9 470.3130 401.6 492.4 505.0 498.4140 428.0 523.3 537.8 535.9150 453.1 561.0 580.3 573.0160 485.2 594.0 609.2 602.8170 512.4 625.1 642.4 637.9180 544.3 654.2 672.5 663.8190 573.7 687.7 700.7 695.1200 604.0 723.5 737.8 732.0210 636.5 751.0 770.6 763.4220 662.4 779.4 799.0 789.0230 688.0 802.8 823.4 815.2240 708.0 827.1 848.1 839.0250 733.5 851.9 872.0 866.4260 758.5 873.9 889.9 884.5270 780.2 892.2 906.3 901.5280 797.6 904.8 918.4 915.4290 816.7 915.3 927.5 925.3298 831.4 927.0 939.0 933.7310 851.5 939.5 951.4 947.6320 862.5 949.5 962.3 956.6330 877.1 956.2 971.2 964.0

Table 2. Temperature dependences of the heat capacity (Cp(±2%), J/(mol K)) of anhydrous metal acetates M2(OOCCH3)6(M = La (1), Sm (2), Eu (3), and Tm (4))

T, K 1 2 3 4

113 275.5 305.9 347.3 326.5120 310.2 333.8 373.3 355.5130 338.3 365.2 404.5 386.4140 369.9 394.4 436.7 415.2150 400.9 423.0 474.2 447.8160 426.8 452.0 500.9 477.8170 456.0 486.0 537.0 508.9180 488.4 521.1 562.0 543.1190 520.3 555.7 595.1 577.1200 544.5 585.2 624.4 604.3210 571.7 611.5 649.0 628.3220 605.5 634.6 670.3 651.5230 629.4 659.2 695.4 676.8240 652.0 682.4 716.3 701.9250 678.1 705.0 740.8 723.0260 705.3 730.1 761.7 746.6270 726.2 752.1 778.9 767.0280 750.8 773.0 803.0 789.2290 766.1 786.2 818.2 800.4298 784.4 801.2 831.1 817.0310 800.2 817.3 847.5 832.7320 815.2 834.6 864.5 849.1330 830.0 847.5 876.4 862.0

RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY Vol. 80 No. 3 2006

THE THERMODYNAMIC PROPERTIES OF RARE-EARTH METAL BINUCLEAR ACETATES 325

(10–50 mg) were used. Weighing was performed withan accuracy of 2 × 10–5 g.

Measurements were taken during heating at a rate of2–5 K/min. In every experiment, the temperature inter-val was no more than 100°C, and the overlap betweenthe temperature intervals of two successive experi-ments was approximately 40 K. Three to five series ofmeasurements (with different sample weights) wereperformed for each substance. The possible systematicerror was estimated by studying the heat capacity ofreference compounds. According to the data obtainedin five series of measurements, the deviation of the heatcapacity of corundum from that recommended by theNational Bureau of Standards (USA) was ±1.5 and ±2%over the temperature ranges 300–850 and 120–270 K,respectively.

The determination of the phase composition of thesolid products of the decomposition of acetates and piv-alates in air was performed by the X-ray and calorime-try methods. The X-ray powder patterns of the decom-position products were obtained on an FR-552 camera-monochromator (CuKα1 radiation) using germanium asan internal reference (the reflection positions were

measured on an IZA-2 comparator with an accuracy of±0.01 mm). The heat capacity of the solid decomposi-tion products obtained was measured over the tempera-ture range 300–500 K (Table 5).

The possibility of using thermal decompositionmethods for determining the enthalpies of formation ofcoordination compounds from the enthalpies of decom-position was established in [9, 10]. We measuredenthalpy changes at separate decomposition stages(Table 6). The thermal decomposition of the com-pounds in air was studied by differential scanning calo-rimetry and thermogravimetry on DSC-20 and TG-50modules of a TA-3000 (Mettler) thermoanalyzer. For

Table 3. Temperature dependences of the heat capacity (Cp(±2.5%), J/(mol K)) of metal pivalates [M2(µ2-OOCCMe3)4 ·(OOCCMe3)2(HOOCCMe3)6]HOOCCMe3 (M = La (1), Sm(2), and Eu (3))

T, K 1 2 3

113 1016 1047 1080

120 1058 1099 1143

130 1126 1162 1215

140 1185 1222 1273

150 1248 1292 1343

160 1307 1350 1404

170 1376 1421 1481

180 1442 1491 1552

190 1503 1554 1611

200 1561 1620 1678

210 1640 1701 1764

220 1705 1764 1817

230 1759 1822 1885

240 1820 1891 1947

250 1898 1950 2019

260 1957 2023 2072

270 2017 2085 2145

280 2073 2136 2196

290 2125 2177 2251

298 2156 2218 2287

310 2209 2271 2336

320 2232 2304 2389

Table 4. Temperature dependences of the heat capacity (Cp(±2.5%), J/(mol K)) of metal tris-pivalates M2(µ2-OOCCMe3)6(M = La (1), Sm (2), and Eu (3))

T, K 1 2 3

113 495 523 553

120 528 554 597

130 570 605 654

140 625 660 712

150 675 707 763

160 715 755 810

170 762 801 863

180 805 847 919

190 858 901 971

200 903 959 1018

210 951 998 1067

220 985 1044 1101

230 1053 1094 1158

240 1097 1138 1197

250 1138 1179 1232

260 1172 1215 1274

270 1203 1248 1305

280 1236 1272 1337

290 1258 1301 1363

298 1279 1320 1383

310 1304 1352 1406

330 1346 1391 1442

350 1387 1428 1484

370 1429 1467 1523

390 1464 1505 1565

400 1489 1536 1581

420 1530 1574 1614

440 1568 1610 1652

460 1615 1652 1693

480 1657 1687 1734

500 1696 1737 1776

326


DOBROKHOTOVA et al.

every compound, four differential scanning calorimetryand three thermogravimetry experiments were per-formed. Differential scanning calorimetry was alsoused to study thermal decomposition stage by stage,which presupposed the division of the whole tempera-ture range of studies into separate intervals. The lengthsand numbers of these intervals were determined afterstudies of general patterns for mass and energy changes

during decomposition. Enthalpy changes at separatestages were determined under scanning (298–773 K)and isothermal conditions. The accuracy of determin-ing anomalous points and thermal effect values was ±1K and ±0.5%, respectively.

RESULTS AND DISCUSSION

Calculations of the Thermodynamic Functions of Formation

The experimental Cp(T) dependences for com-pounds 1–7 and intermediate thermal decompositionproducts were extrapolated to 0 K using an approxima-tion method similar to that employed in [11]. They werethen used to calculate absolute entropies at 298 K(Table 7).

We found that the decomposition of binuclear com-plexes 1–4 was a step process (Figs. 1a, 1b). The firstdecomposition stage was the elimination of solvationwater. The second stage was the loss of coordinationwater. The anhydrous acetates formed were thermallystable over a fairly wide temperature range. Their ther-mal decomposition began above the limiting stabilitytemperature.

Table 5. Heat capacity (Cp (±2%), J/(mol K)) of the solid products of the decomposition of 1–7

T, K La2O3 Sm2O3 Eu2O3 Tm2O3 1 2 3 4 5 6 7

[8] This work

300 109.0 114.8 121.9 129.0 110.1 113.5 120.6 129.5 108.5 114.0 120.7

320 111.1 117.5 123.8 131.3 110.7 115.8 122.9 130.6 109.7 116.7 122.7

340 112.9 119.8 125.4 133.5 112.5 118.0 124.5 132.9 110.9 118.9 124.0

360 114.4 121.8 126.8 135.4 113.7 120.6 125.7 134.3 112.5 120.6 125.3

380 115.8 123.5 128.1 137.2 114.8 122.9 127.2 136.7 113.8 122.9 127.4

400 117.0 125.1 129.3 138.8 116.2 125.3 128.4 138.0 115.1 124.5 128.6

420 118.1 126.5 130.4 140.3 117.7 126.8 129.3 139.4 117.2 125.7 129.5

440 119.0 127.8 131.4 141.8 118.6 128.0 130.8 140.5 118.4 127.1 131.0

460 119.9 128.9 132.3 143.2 119.4 129.4 131.5 142.5 119.3 128.8 132.0

480 120.7 130.0 133.2 144.5 120.5 130.5 132.9 144.0 120.1 130.7 133.5

500 121.4 131.0 134.1 145.8 121.3 132.0 134.0 145.1 120.9 131.6 134.6

Table 6. Enthalpies (kJ/mol) of the decomposition of rare-earth metal acetates and pivalates in air

Metal–∆decompH (A) ∆H (B) ∆H (C) –∆decompH (D) –∆decompH (E)

743 K 298 K 443 K 433 K 750 K 750 K

La 65.0 ± 3.2 42.6 ± 7.0 164.0 ± 7.5 558.5 ± 6.0 454.8 ± 10.5 438

Sm 116.7 ± 3.5 90.0 ± 8.5 317.5 ± 8.4 529.2 ± 6.5 480.7 ± 12.0 501

Eu 118.5 ± 3.5 93.0 ± 8.2 307.2 ± 8.2 739.3 ± 6.8 485.5 ± 13.0 503

Tm 156.6 ± 4.1 119.5 ± 9.0 277.5 ± 8.8

Note: A, B, C, D, and E are the enthalpies of the decomposition of anhydrous acetates, dehydration of acetates, removal of coordinationwater from acetates, the first and second decomposition stages of metal pivalates, decomposition of tris-pivalates (experimental),and decomposition of tris-pivalates (calculated), respectively.

Table 7. Standard entropy (S°(298), J/(mol K)) of (I) acetatesM2(η1,η2-OOCCH3)2(η2-OOCCH3)4(H2O)4 · xH2O, (II) an-hydrous acetates M2(OOCCH3)6 (M = La (1), Sm (2), Eu (3),and Tm (4)), (III) pivalates [M2(µ2-OOCCMe3)4(OOCCMe3)2 ·(HOOCCMe3)6]2HOOCCMe3, and (IV) tris-pivalatesM2(µ2-OOCCMe3)6 (M = La (5), Sm (6), and Eu (7))

Metal I II III IV

La 841 ± 15 708 ± 13 2192 ± 32 1045 ± 38

Sm 1011 ± 14 730 ± 14 2285 ± 34 1097 ± 34

Eu 1024 ± 11 743 ± 14 2401 ± 37 1147 ± 35

Tm 969 ± 12 725 ± 12

Note: For metal acetates, x = 0.5 if M = La and x = 4 otherwise.



An analysis of the composition of solid decomposi-tion products formed from 1–7 showed them to be sin-gle-phase (M2O3) to within X-ray diffraction sensitiv-ity. The experimental results and the data on the thermaldecomposition of iron acetate [12] led us to suggest thefollowing resultant scheme for the decomposition ofbinuclear acetates in air:

(1)

The enthalpies of decomposition (Table 6) and for-mation of the decomposition products [8, 13] were usedto calculate the enthalpies of formation of rare-earthmetal acetates and anhydrous acetates at 743 and 298 Kby the Hess law (Table 8). In these calculations, we alsoused the temperature dependences of the heat capaci-ties of the decomposition products [8, 13] and initialcompounds. The entropies of formation ∆fS° were cal-culated from the absolute entropies of 1–7 and simplesubstances [8], which allowed us to calculate the Gibbsenergy of formation of these compounds (Table 8). Wetherefore obtained the complete set of thermodynamicdata (Cp(T), S°(298), ∆fH°(298), and ∆fG°(298)) forbinuclear acetates.

The decomposition of 5–7 also occurred in stages(Figs. 1c, 1d). The first stage was the splitting off ofouter-sphere pivalic acid. The second stage was theremoval of pivalic acid coordinated to metals, whichresulted in the formation of tris-pivalates thermally sta-ble over a fairly wide temperature range. Next, thedecomposition of tris-pivalates occurred. We wereunable to determine the scheme of the thermal decom-position of rare-earth metal pivalates because of theabsence of data on the composition of the gas phaseformed. For this reason, we could only estimate theenthalpies of their formation.

This was done as follows. First, we considered therelation between the enthalpies of formation of anhy-drous acetates (our data) and carbonates [8]. For thecerium subgroup metals (La, Sm, Eu), the differenceof the enthalpies of formation was almost constant(408 ± 1). We also compared the enthalpies of forma-tion of standard solutions of metal formates and ace-tates [8] to find that the difference of these values wasalso constant for the metals under consideration towithin measurement errors (356.0 ± 3.0). This led us tosuggest that the difference of the enthalpies of forma-tion of tris-pivalates and anhydrous acetates shouldalso be some constant value. This value was determinedon the assumption that calculations based on additivebond increments (the method suggested by Tatevskiifor hydrocarbons [14]) were applicable. The constantvalue was found to be 199 kJ/mol, which allowed us tocalculate the enthalpies of formation of metal tris-piv-alates (Table 9). The entropies of formation ∆fS° werecalculated from the absolute entropies of the com-pounds under consideration (Table 7) and simple sub-

M2 OOCCH3( )6 xH2O M2O3⋅

+ 3CH3COCH3↑ 3CO2↑ xH2O↑.+ +

200

Q, mV

–5.0

–12.5

0 400

2.5

10.0

–20.0

(a)

100

m, mg

6

5

0 200

7

8

3

(b)

4

300 400

100

Q, mV

–3

0 200

7(c)

300 400

–13

500

100

m, mg

3

0 200

5

(d)

300 400

1

500 t, °C

Fig. 1. Characteristics of thermal decomposition of La (a, b)acetate and (c, d) pivalate: (a, c) temperature dependence ofthe heat flux and (b, d) weight loss as a function of temper-ature.

328


DOBROKHOTOVA et al.

stances [8]. This allowed us to calculate the Gibbsenergy of formation of metal pivalates (Table 8).

The enthalpies of formation of binuclear metal piv-alates were calculated from the estimated enthalpies offormation of metal tris-pivalates, the enthalpy of for-

mation of pivalic acid [15], and the total heat effect atthe first two stages of decomposition (the removal of sol-vation pivalic acid at the first stage and coordinated piv-alic acid at the second) (Table 6). The entropy of forma-tion ∆fS° was calculated from the absolute entropies ofthe compounds under consideration (Table 7) and simplesubstances [8]. This allowed us to calculate the Gibbsenergy of formation of binuclear pivalates (Table 8).

The thermodynamic data obtained were used to con-sider the thermodynamic stability of metal tris-piv-alates M2(OOëëMe3)6 (M = La, Sm, and Eu) (Fig. 2).The results were in agreement with our experimentaldata on the thermal decomposition of these com-pounds [7].

A possible overall scheme of thermal decomposi-tion was determined using the IVTANTERMO pro-gram for calculating the equilibrium composition ofmulticomponent heterogeneous systems [8]. Possiblegas-phase products were suggested on the basis of thedata obtained in [5]. These were C4H8 (2-methylpro-pene-1), C9H18O (2,2,4,4-tetramethylpentanone-3),CH2O (formaldehyde), and C5H10O (2,2-dimethylpro-panal). The scheme can be written as

M2(µ2–OOëëMe3)6 å2é3 + CO2 + possible organic decomposition products. (2)

The thermodynamic data on both solid and sup-posed gaseous thermal decomposition products neces-sary for calculations were taken from [8, 13, 16, 17].The calculations were performed for 750 K and pres-sure of 1.01 × 105 Pa (Table 9). The calculation resultsshowed that the thermal decomposition of metal tris-pivalates could be described by the equation

(3)M2 µ2-OOCCMe3( )6 M2O3

+ 3CO2↑ 3C9H18O↑.+

To check the reliability of the estimated enthalpiesof formation and correctness of equilibrium gas phasecomposition calculations for the decomposition oftris-pivalates, we calculated ∆decompH(750 ä) (Table 6)using the data on the enthalpies of formation of the ini-tial compounds (Table 8) and decomposition products[8, 13, 16]. The results were in satisfactory agreementwith those described above.

To summarize, we used the experimental tempera-ture dependences of heat capacities and the enthalpies

Table 8. Thermodynamic functions of formation of binuclear acetates and pivalates (kJ/mol)

M –∆fH°(298) –∆fG°(298) –∆fH°(298) –∆fG°(298) –∆fH°(298) –∆fG°(298) –∆fH°(298) –∆fG°(298)

I II III IVLa 5136 ± 31

(6313)*4302 ± 56 3683 ± 21 3123 ± 25 7153 4918 3892 2700

Sm 6259 ± 33 5225 ± 65 3671 ± 24 3111 ± 36 7170 4935 3870 2708Eu 6030 ± 33 4996 ± 67 3514 ± 24 2951 ± 37 6803 4598 3713 2551Tm 6388 ± 34 5340 ± 71 3704 ± 26 3138 ± 38

Note: The parenthesized value was estimated for M2(η1,η2-OOCCH3)2(η2-OOCCH3)4(H2O)4 · 4H2O. See Table 7 for notation.

350T, K

G, kJ/mol

–750

250

–1750

–2750

450 550 650 850750

123

Fig. 2. Temperature dependences of the Gibbs energy offormation of metal pivalates M2(OOëëMe3)6 (M = (1) La,(2) Sm, and (3) Eu).

Table 9. Calculations of the equilibrium composition (mol) of metal tris-pivalate decomposition products at 750 K

M [M2C30O12H54] [M2O3] [GP] [CO2] [C9H18O] [C4H8] × 10–3 [H2CO] × 10–3 [C5H10O] × 10–3

La 0.00000 1.00000 6.0079151 3.00000 2.99547 7.91820 3.39133 1.13561Sm 0.00000 1.00000 6.0079152 3.00000 2.99547 7.91826 3.39133 1.13561Eu 0.00000 1.00000 6.0079151 3.00000 2.99547 7.91820 3.39133 1.13561

Note: GP stands for gas phase.



of decomposition to obtain the complete set of thermo-dynamic data (Cp(T), S°(298), ∆fH°(298), and∆fG°(298)) on binuclear La, Sm, Eu, and Tm acetatesand La, Sm, and Eu pivalates. A resultant scheme of thethermal decomposition of metal pivalates was sug-gested and its reliability proved. These results will beused to develop a strategy for synthesizing mixed oxideinorganic materials from carboxylate molecular precur-sors.

ACKNOWLEDGMENTS

This work was financially supported by the RussianFoundation for Basic Research (project nos. 05-03-32794, 04-03-32880, 05-03-08203) and a special pro-gram for basic research of the Presidium of RussianAcademy of Sciences and OKhNM (Russian Academyof Sciences).

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