Synthesis of thorium (uranyl) sulfoxide complexes and crystal

structure of novel thorium complex containing both

10 and 12 coordinated thorium

Liming Zhu, Xia Zhu, Yuping Zhang, Baolong Li*, Zhengbai Cao, Yong Zhang

College of Chemistry and Chemical Engineering, Suzhou University, Street Shizi No. 1, Suzhou 215006, China

Received 22 May 2003; revised 29 June 2003; accepted 30 June 2003

Abstract

Two complexes [Th(NO3)3(dchso)4][Th(NO3)5(dchso)2] (1) and [UO2(NO3)2(dchso)2] (2) (dchso ¼ dicyclohexyl sulfoxide)

have been synthesized and characterized. The crystal structure of [Th(NO3)3(dchso)4][Th(NO3)5(dchso)2] (1) has been

determined. The X-ray analysis reveals that 1 contains [Th(NO3)3(dchso)4]þ cations and [Th(NO3)5(dchso)2]2 anions. In the

cations, the Th atom has a coordination number 10 with irregular polyhedron involving six oxygen atoms from three bidentate

nitrate groups and four oxygen atoms from the four dchso ligands. In the anions, the Th atoms have a coordination number 12

with icosahedron involving 10 oxygen atoms from five bidentate nitrate groups and two oxygen atoms from the two dchso

ligands.

q 2003 Elsevier B.V. All rights reserved.

Keywords: Crystal structure; Thorium complex; Uranium complex; Nitrate; Dicyclohexyl sulfoxide

1. Introduction

The dimethyl sulfoxide actinoid complexes have

been reported earlier [1,2]. Extraction of U(VI) and

Th(IV) with sulfoxides [3–8] have been widely

studied and a number of coordination compounds of

sulfoxides with Th(IV) and UO2(VI) [9–14] also have

been reported. Although several crystal structures of

thorium complexes have been reported [15–21], only

one sulfoxide thorium complex [ThCl4(dpso)4] [22]

was structurally reported due to their poor crystal

quality. Our interest is studying the extraction

behavior of new extractants with U(VI) and Th(VI)

and the structures of the extracted compounds [5,6,

23–27]. The extraction Th(IV) and UO2(VI) in U–Th

fuel or separate uranium from thorium is usually

carried under nitric acid media. The structural

properties of the extracted compounds (complexes)

are very useful in the extraction study. In studying the

extraction behavior of dicyclohexyl sulfoxide (dchso)

with U(VI) and Th(VI), we obtained a novel thorium

complex [Th(NO3)3(dchso)4][Th(NO3)5(dchso)2] (1)

and determined the crystal structure. However, the

crystal structure determination of dicyclohexyl sulf-

oxide uranium complex [UO2(NO3)2(dchso)2] (2)

was unsuccessful due to its poor crystal quality.

0022-2860/03/$ - see front matter q 2003 Elsevier B.V. All rights reserved.

doi:10.1016/S0022-2860(03)00430-7

Journal of Molecular Structure 657 (2003) 375–380

www.elsevier.com/locate/molstruc

* Corresponding author. Tel.: þ86-51262523062; fax: þ86-

51265224783.

E-mail address: blli1965@pub.sz.jsinfo.net (B. Li).

The thorium complex [Th(NO3)3(dchso)4][Th(NO3)5

(dchso)2] (1) contains [Th(NO3)3(dchso)4]þ cations

with coordination number 10 and [Th(NO3)5

(dchso)2]2 anions with coordination number 12.

2. Experimental

2.1. Physical measurements

Elemental analyses for C, H and N were performed

on a Perkin-Elmer 240C analyser. IR spectra were

obtained for KBr pellets on a Nicolet 170SX FT-IR

spectrophotometer in the 4000–400 cm21 region.

2.2. Synthesis

2.2.1. Synthesis of

[Th(NO3)3(dchso)4][Th(NO3)5(dchso)2] (1)

Ligand dicyclohexyl sulfoxide (0.13 g, 0.6 mmol)

in 10 ml ethyl ether was added to a 10 ml solution of

Th(NO3)4·4H2O (0.11 g, 0.2 mmol) in the same

solvent. After stirring for 1 h at room temperature,

the solution was filtrated. The solid was solved in the

toluene solvent. After about a week, the yellow

crystals [Th(NO3)3(dchso)4][Th(NO3)5(dchso)2] (1)

suitable for X-ray diffraction analyses were isolated

by slow evaporating the solution at room temperature.

Elemental analysis confirmed the organic content

(Found: C, 38.33; H, 5.78; N, 4.72. Calcd for

C72H132N8O30S6Th2 (%): C, 38.50; H, 5.92; N, 4.99.

2.2.2. Synthesis of [UO2(NO3)2(dchso)2] (2)

The complex 2 was synthesized similar to the

synthesis procedure of 1 except UO2(NO3)2·6H2O

was used instead of Th(NO3)4·4H2O. Elemental

analysis confirmed the organic content (Found: C,

34.76; H, 5.38; N, 3.28. Calcd for C24H44N2O10S2U

(%): C, 35.04; H, 5.35; N, 3.41.

2.3. Structure determination

Single crystal 1 with dimensions 0.39 mm £ 0.17

mm £ 0.11 mm was selected for data collection at

193.15 K, using a RIGAKU Mercury CrystalClear

with graphite monochromated Mo Ka radiation

(l ¼ 0:71073 A). Data were collected by v scan

technique. The structure was solved by direct

methods using SHELX-97 program package [28] and

refined with full-matrix least-squares method with

anisotropic thermal parameters for the non-hydrogen

atoms. The positions of hydrogen atoms were

calculated using idealized geometry. The parameters

of the crystal, data collection and refinement are

given in Table 1. Bond lengths and angles are shown

in Table 2.

3. Results and discussion

3.1. Structural analysis

The X-ray analysis reveals that the complex 1

consists of discrete [Th(NO3)3(dchso)4]þ cations and

[Th(NO3)5(dchso)2]2 anions (Fig. 1). In the cations,

the Th atom has a coordination number of 10

involving six oxygen atoms from three bidentate

nitrate groups and four oxygen atoms from the

four dchso ligands. The Th – O(nitrate) bonds

Table 1

Crystal data and structure refinement for the compound 1

Empirical formula C72H132N8O30S6Th2

Temperature (K) 193.15

Formula weight (g mol21) 2246.30

Wavelength (A) 0.71073

Crystal system Monoclinic

Space group P2=n

a (A) 17.2387(12)

b (A) 11.6642(8)

c (A) 23.5753(19)

b (deg) 92.631(4)

Volume (A3) 4735.4(6)

Z 2

D (Mg/M3) 1.575

Absorption coefficient (mm21) 3.346

Fð000Þ 2272

Crystal size (mm3) 0.39 £ 0.17 £ 0.11

u range for data collection (deg) 3.10–27.48

Index ranges 222 # h # 22;

215 # k # 15;

230 # 1 # 30

Refinement method Full-matrix least-squares

on F2

Independent reflections 10,225 ½RðintÞ ¼ 0:0628�

Goodness-of-fit on F2 1.192

Final R1 and wR2 ½I . 2sðIÞ� 0.0687, 0.1200

R1 and wR2 indices (all data) 0.0776, 0.1236

Largest diff. peak and hole (e A23) 2.756 and 21.099

L. Zhu et al. / Journal of Molecular Structure 657 (2003) 375–380376

(2.556(5)–2.618(6) A) are distinctly longer than the

Th–O(ligands) bonds (2.387(5)–2.411(5) A), which

is similar to other Th complexes containing combi-

nations of bidentate nitrates and organic oxygen donor

ligands in the coordination sphere [15–20]. Although

four oxygen atoms O(1), O(2), O(6) and O(2A) are

coplanar well with the mean deviation from the least

square plane by 0.0295 A (Fig. 2), the other six atoms

O(4), O(7), O(1A), O(4A), O(6A) and O(7A) are

deviated from above mean plane by 3.0278, 2.5752,

1.8900, 2.5751, 21.5825 and 0.3988 A, respectively.

O(6A) atom is below the mean plane while the other

five atoms are above the mean plane and O(4) atom is

deviated the greatest from the mean plane. The O(4)–

Th(1)–O(6A) bond angle deviates significantly from

linearity, being 143.65(18)8. The O(7), O(1A), O(4A)

and O(7A) atoms are far from coplanar. As the

coordination polyhedron about the thorium atom is

neither described as a distorted bicapped square

antiprism nor as a distorted dodecahedron, it should

be described as an irregular polyhedron. The nitrate

groups are, as expected, planar and the terminal

Table 2

Selected bond lengths (A) and angles (deg) for the complex 1

Th(1)–O(1) 2.618(6) Th(1)–O(1A) 2.618(6)

Th(1)–O(2) 2.556(5) Th(1)–O(2A) 2.556(5)

Th(1)–O(4) 2.587(6) Th(1)–O(4A) 2.587(6)

Th(1)–O(6) 2.411(5) Th(1)–O(6A) 2.411(5)

Th(1)–O(7) 2.387(5) Th(1)–O(7A) 2.387(5)

Th(2)–O(8) 2.616(5) Th(2)–O(8A) 2.616(5)

Th(2)–O(9) 2.612(5) Th(2)–O(9A) 2.612(5)

Th(2)–O(11) 2.614(5) Th(2)–O(11A) 2.614(5)

Th(2)–O(12) 2.606(5) Th(2)–O(12A) 2.606(5)

Th(2)–O(14) 2.601(5) Th(2)–O(14A) 2.601(5)

Th(2)–O(16) 2.413(5) Th(2)–O(16A) 2.413(5)

N(1)–O(1) 1.267(9) N(1)–O(2) 1.281(8)

N(1)–O(3) 1.211(8) N(2)–O(4) 1.284(8)

N(2)–O(4A) 1.284(8) N(2)–O(5) 1.183(13)

N(3)–O(8) 1.269(8) N(3)–O(9) 1.279(8)

N(3)–O(10) 1.221(7) N(4)–O(11) 1.280(7)

N(4)–O(12) 1.275(7) N(4)–O(13) 1.218(7)

N(5)–O(14) 1.265(7) N(5)–O(14A) 1.265(7)

N(5)–O(15) 1.242(12)

O(1)–Th(1)–O(1A) 174.1(3) O(1)–Th(1)–O(2) 49.10(18)

O(1)–Th(1)–O(4) 110.2(2) O(1)–Th(1)–O(6) 114.43(17)

O(1)–Th(1)–O(7) 105.17(19) O(1)–Th(1)–O(2A) 133.8(2)

O(1)–Th(1)–O(4A) 64.0(2) O(1)–Th(1)–O(6A) 70.61(19)

O(1)–Th(1)–O(7A) 72.81(18) O(2)–Th(1)–O(4) 133.6(2)

O(2)–Th(1)–O(6) 69.95(18) O(2)–Th(1)–O(7) 74.44(18)

O(4)–Th(1)–O(6) 130.36(18) O(4)–Th(1)–O(7) 73.64(18)

O(6)–Th(1)–O(7) 74.77(17) O(2)–Th(1)–O(2A) 137.0(3)

O(4)–Th(1)–O(4A) 49.4(3) O(4)–Th(1)–O(6A) 143.65(18)

O(6)–Th(1)–O(6A) 73.8(2) O(7)–Th(1)–O(7A) 141.2(2)

O(8)–Th(2)–O(9) 49.00(15) O(8)–Th(2)–O(11) 65.08(15)

O(8)–Th(2)–O(12) 101.81(15) O(8)–Th(2)–O(14) 64.91(16)

O(8)–Th(2)–O(16) 111.84(16) O(8)–Th(2)–O(9A) 124.25(15)

O(8)–Th(2)–O(12A) 123.50(15) O(8)–Th(2)–O(14A) 66.98(16)

O(8)–Th(2)–O(16A) 68.78(16) O(11)–Th(2)–O(9A) 124.42(15)

O(11)–Th(2)–O(12A) 66.74(15) O(11)–Th(2)–O(14A) 124.07(16)

O(11)–Th(2)–O(16A) 68.31(15) O(9A)–Th(2)–O(12A) 66.02(15)

O(9A)–Th(2)–O(14A) 65.91(16) O(9A)–Th(2)–O(16A) 67.71(16)

O(12A)–Th(2)–O(14A) 123.82(16) O(12A)–Th(2)–O(16A) 67.34(16)

O(14A)–Th(2)–O(16A) 68.83(16) O(16)–Th(2)–O(16A) 178.7(2)

L. Zhu et al. / Journal of Molecular Structure 657 (2003) 375–380 377

(N–O) bonds are significantly shorter compared with

the (N–O)–Th bonds (averages 1.205 and 1.277 A,

respectively).

In the anions, the Th atoms have a coordination

number 12 involving 10 oxygen atoms from five

bidentate nitrate groups and two oxygen atoms from

the two dchso ligands. The Th–O(nitrate) bonds

(2.601(5)–2.614(5) A) are distinctly longer than the

Th–O(ligands) bonds (2.413(5) A), which is similar

to [Th(NO3)3(dchso)4]þ cations and other Th com-

plexes containing combinations of bidentate nitrates

and organic oxygen donor ligands in the coordination

sphere [15–20]. The coordination polyhedron about

Th(2) atom is best described as a distorted icosahedral

geometry, one plane of which comprises O(8), O(11),

O(12A), O(9A) and O(14A) capped by O(16A); the

other comprising O(9), O(12), O(11A), O(8A) and

O(14) capped by O(16). Five oxygen atoms O(8),

O(11), O(12A), O(9A) and O(14A) are coplanar well

Fig. 1. The local coordination of thorium atoms in 1 with 30%

thermal ellipsoids (a) [Th(NO3)3(dchso)4]þ cation, (b) [Th(NO3)5

(dchso)2]2 anion.

Fig. 2. The coordination polyhedron about the thorium atom in 1 (a)

[Th(NO3)3(dchso)4]þ cation (b) [Th(NO3)5(dchso)2]2 anion.

L. Zhu et al. / Journal of Molecular Structure 657 (2003) 375–380378

with the mean deviation from the least square plane by

0.0056 A. Five oxygen atoms O(9), O(12), O(11A),

O(8A) and O(14) are also coplanar well with the mean

deviation from the least square plane by 0.0056 A.

The two planes are fully parallel. The Th and O atoms

lie 0.9694 and 1.4438 A, respectively, from these

planes. The O(16)–Th(2)–O(16A) bond angle is

almost linear, being 178.7(2)8. Both the capping

oxygen atoms, O(16) and O(16A), are provided by

dchso ligands. The nitrate groups are, as expected,

planar and the terminal (N–O) bonds are significantly

shorter compared with the (N – O) – Th bonds

(averages 1.227 and 1.272 A, respectively), which

is similar to the bidentate nitrate group in [Th(NO3)3

(dchso)4]þ cations and other Th complexes containing

bidentate nitrates.

It should be noticed that the content of thorium

nitrate complexes reported earlier are usually neutral

Th(NO3)4·nL (L ¼ ligand). Although two thorium

complexes [Th(NO3)2{Ph2P(O)N(Pri)P(O)Ph2}3]

[Th(NO3)6] [15] and [Th(NO3)3(PMe3O)4]2

[Th(NO3)6] [16] containing two different coordination

thorium ions are reported, the thorium complexes

containing two different coordination thorium ions are

few. The thorium coordination cations contain ligands

Ph2P(O)N(Pri)P(O)Ph2 or PMe3O with coordination

number 10 and the thorium coordination anions

contain only six small bidentate nitrate groups with

coordination number 12. The complex 1 not only

contains two different coordination thorium ions, but

also the thorium coordination cations and anions both

containing same large ligand dchso and bidentate

nitrate with different numbers. This is the first thorium

complex determined structurally in which both the

thorium coordination cations and anions contain same

organic ligands and nitrate groups. Also, the high

coordination number of 12 in thorium coordination

cations [Th(NO3)5(dchso)2]2 should be noticed. Only

three thorium complexes with coordination number

12 were structural characteristic. Two thorium

complexes are [Th(NO3)2{Ph2P(O)N(Pri)P(O)

Ph2}3][Th(NO3)6] [15] and [Th(NO3)3(PMe3O)4]2

[Th(NO3)6] [16] which contain six bidentate nitrate

coordination [Th(NO3)6]2 anions. The other is

[Th(NO3)4(L)] which has four bidentate nitrate and

a tetradentate ligand [20]. The complex 1 contains the

first reported [Th(NO3)5(L)n]2 anion. Due to their

poor crystal quality, the first reported sulfoxide

thorium complex with structural characteristic is

[ThCl4(dpso)4] [22] which contains eight coordi-

nation thorium atoms with dodecahedral geometry

from four Cl atoms and four oxygen atoms of four

diphenyl sulfoxide. The complex 1 may be the second

successful structural characteristic sulfoxide thorium

complex.

3.2. Infrared spectrum

IR spectra show the bands of 1 as follows:

2932vs, 2855s, 1508vs, 1451s, 1385m, 1319s,

1292s, 1034s, 1003s, 972s, 949vs, 810w, 746w,

718vw, 517w cm21. The frequencies of the nitrate

vibrations (n1 : 1508vs, n4 : 1319s and 1292s, n2 :

1034s and 1003s, n6 : 810w, n3 : 746w, n5 : 718vw)

are consistent with the presence of bidentate nitrate

group [16–20]. The observed splitting of the n4 and

n2 nitrate indicates the presence of two thorium

coordination environments, which is confirmed by

X-ray diffraction analysis. SyO stretching frequency

in free dchso ligand appears as a strong absorption

at 1030 cm21 and is shifted to 972 and 949 cm21 in

the complex 1 [11], which also indicates the

presence of two thorium coordination environments

and is confirmed by X-ray diffraction analysis. IR

spectra show the bands of 2 as follows: 2933s,

2857s, 1507vs, 1447s, 1385w, 1290s, 1025w,

1000m, 968s, 934vs, 743m cm21. The frequencies

of the nitrate vibrations (n1 : 1507, n4 : 1290s, n2 :

1025w, n3 : 743m.) are consistent with the presence

of bidentate nitrate group [16–20]. SyO stretching

frequency in free dchso ligand appears as a strong

absorption at 1030 cm21 and is shifted to 968 cm21,

which indicates coordination of dchso to the metal

ion through its oxygen atom. The strong absorption

at 934 cm21 indicates the presence of uranyl in 2.

The suggested coordination number of uranium in 2

is eight.

Acknowledgements

This work was supported by Funds of Key

Laboratory of Organic Syntheses, the Education

Committee of Jiangsu Province (No. KJS01018) and

Funds of Young Teacher of Suzhou University,

China.

L. Zhu et al. / Journal of Molecular Structure 657 (2003) 375–380 379

References

[1] K.W. Bagnall, D. Brown, P.J. Jones, J.G.H. Du Preez, J. Chem.

Soc. (A) (1966) 737.

[2] K.W. Bagnall, D. Brown, D.C. Holah, F. Lux, J. Chem. Soc.

(A) (1968) 465.

[3] D.M. Petkovic, J. Serb. Chem. Soc. 54 (1989) 503.

[4] J.S. Preston, P. Du, C. Anna, J. Chem. Technol. Biotechnol. 69

(1997) 86.

[5] B.-R. Bao, Y.-Z. Bao, C.-H. Shen, G.-D. Wang, J. Qian, Z.-B.

Cao, J. Radioanal. Nucl. Chem. 14 (1992) 143.

[6] C.-H. Shen, B.-R. Bao, Y.-Z. Bao, G.-D. Wang, J. Qian, Z.-B.

Cao, J. Radioanal. Nucl. Chem. 178 (1994) 91.

[7] S.N. Yu, L. Ma, B.-R. Bao, J. Radioanal. Nucl. Chem. 241

(1999) 347.

[8] S.-N. Yu, Y. He, L. Ma, He Huaxue Yu Fangshe Huaxue

(Chinese) 21 (1999) 92.

[9] J.A. Davies, Adv. Inorg. Chem. Radiochem. 24 (1981) 116.

[10] R.K. Agarwal, Synth. React. Inorg. Met.-Org. Chem. 21

(1991) 1193.

[11] R.K. Agarwal, J. Prakash, Polehedron 10 (1991) 2567.

[12] R.K. Agarwal, K. Arora, Synth. React. Inorg. Met.-Org.

Chem. 23 (1993) 1671.

[13] B.B. Misra, S.R. Mohanty, N.V.V.S. Murti, S. Raychaudhuri,

Inorg. Chim. Acta 28 (1978) 275.

[14] K.W. Bagnall, O. Velasquez Lopez, L. Xing-Fu, J. Chem.

Soc., Dalton Trans. (1983) 1153.

[15] K. Aparna, S.S. Krishnamurthy, M. Nethaji, J. Chem. Soc.,

Dalton Trans. (1995) 2991.

[16] N.W. Alcock, S. Esperas, K.W. Bagnall, W. Hsian-Yun,

J. Chem. Soc., Dalton Trans. (1978) 638.

[17] A.G.M. Al-Daher, K.W. Bagnall, J. Chem. Soc., Dalton Trans.

(1986) 615.

[18] D.M.L. Goodgame, D.J. Williams, R.E.P. Winpenny, Poly-

hedron 7 (1988) 1807.

[19] D.M.L. Goodgame, S. Newnham, C.A. O’Mahoney, D.J.

Williams, Polyhedron 9 (1990) 491.

[20] W.-S. Liu, M.-Y. Tan, K.-B. Yu, G.-Z. Tan, J. Chem. Soc.,

Dalton Trans. (1993) 3427.

[21] D.L. Clark, J.G. Watkin, Inorg. Chem. 32 (1993) 1766.

[22] C.E.F. Richard, D.C. Woollard, Acta Crystallogr. Sect. B 36

(1980) 292.

[23] Z.B. Cao, C.H. Shen, B.R. Bao, G.D. Wang, J. Qian, Chin.

J. Nucl. Radiochem. 15 (1993) 76.

[24] Z.B. Cao, Y.Z. Bao, C.H. Shen, B.R. Bao, G.D. Wang, J. Qian,

Chin. Nucl. Tech. 16 (1993) 380.

[25] Z.B. Cao, H.Z. Wang, L.M. Zhu, J.S. Gu, Z.R. Lu, K.B. Yu,

Chem. J. Chin. Univ. 14 (1993) 1051.

[26] Z.B. Cao, H.Z. Wang, J.S. Gu, L.M. Zhu, K.B. Yu, Acta

Crystallogr. C49 (1993) 1942.

[27] Z.B. Cao, T.L. Qi, L.M. Zhu, D.C. Zhang, R. Zhou, K.B. Yu,

Acta Crystallogr. C55 (1999) 1270.

[28] G.M. Sheldrick, SHELXS-97 and SHELXL-97, University of

Gottingen, Germany, 1997.

L. Zhu et al. / Journal of Molecular Structure 657 (2003) 375–380380