The first (trisulfoxide)metal complexes: Synthesis and crystal structures of the 1D lanthanide coordination polymers [Ln(L)(MeOH)(NO3) 3]n and {[La(L)(DMF)5](ClO4) 3}n [L = 1,3,5-tris(ethylsulfinyl)-2,4,6-trimethylbenzene, Ln = LaIII and NdIII]

Article abstract of DOI:10.1002/ejic.200300751

A new trisulfoxide ligand, 1,3,5-tris(ethylsulfinyl)-2,4,6-trimethylbenzene (L), was designed and synthesized, and treated with Ln(NO3) ₃ or Ln(ClO4)₃ to produce three coordination polymers: [Ln(L)(MeOH)(NO₃)₃]_n [where Ln = La^III (1); Nd^III (2)] and {[La(L)(DMF)₅] (ClO₄)₃}_n (3). Solid-state structures of all three complexes were determined by single-crystal X-ray diffraction. The three complexes have 1D helical-chain structures and complexes 1 and 2 are isostructural. To the best of our knowledge, these coordination polymers are the first examples of (trisulfoxide)metal complexes. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200300751

FULL PAPER
The First (Trisulfoxide)metal Complexes: Synthesis and Crystal Structures of
the 1D Lanthanide Coordination Polymers [Ln(L)(MeOH)(NO3)3]n and
{[La(L)(DMF)5](ClO4)3}n [L ؍ 1,3,5-Tris(ethylsulfinyl)-2,4,6-trimethylbenzene,
Ln ؍ LaIII and NdIII]
Jian-Rong Li,[a] Xian-He Bu,*[a,b] and Ruo-Hua Zhang[a]
Keywords: Coordination polymers / Helical structures / Lanthanides / Sulfoxide
A new trisulfoxide ligand, 1,3,5-tris(ethylsulfinyl)-2,4,6-tri-
methylbenzene (L), was designed and synthesized, and
crystal X-ray diffraction. The three complexes have 1D hel-
ical-chain structures and complexes 1 and 2 are isostructural.
treated with Ln(NO3)3 or Ln(ClO4)3 to produce three coor- To the best of our knowledge, these coordination polymers
dination polymers: [Ln(L)(MeOH)(NO3)3]n [where Ln = LaIII
(1); NdIII (2)] and {[La(L)(DMF)5](ClO4)3}n (3). Solid-state
structures of all three complexes were determined by single-
are the first examples of (trisulfoxide)metal complexes.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
Introduction
In recent years, much effort has been invested in attempts
to design and synthesize metal-organic coordination poly-
mers having specific network topologies and potential appli-
cable properties.[1,2] In this regard, the studies performed by
us and others[3] on the construction of coordination architec-
tures using flexible disulfoxide ligands and metal ions as
building blocks have acquired some interesting results. We
are, therefore, interested in further exploiting the multisulfox-
ide ligands. Such ligands may produce interesting coordi-
nation polymers because of their multiple coordination
modes. As a continuation of this study, we designed a new
trisulfoxide ligand, 1,3,5-tris(ethylsulfinyl)-2,4,6-trimethyl-
benzene (L) (see structure shown below), which is a simple
tridentate ligand. Since each S atom is an asymmetric center,
the tridentate L molecule should be a chiral bridging ligand.
Therefore, the ligand may be used to construct non-centric
framework polymers (or chiral crystals). To the best of our
knowledge, (trisulfoxide)metal complexes have not yet been
reported and the lanthanide complexes presented here are
the first structurally characterized examples of metal com-
plexes with such ligands. Herein, we report the synthesis and
crystal structures of three novel lanthanide complexes with
L, [Ln(L)(CH3OH)(NO3)3]n [where Ln ϭ La (1); Nd, (2)]
and {[La(L)(DMF)5](ClO4)3}n (3).
Results and Discussion
Synthesis and General Characterization
The ligand L was synthesized according to a similar
method used for the synthesis of disulfoxide[4] and the prod-
uct might have been a mixture containing several isomers
of the trisulfoxides. The attempts for separation were not
successful so the mixture was used directly to prepare the
metal complexes. The IR data of L show the characteristic
band of the sulfinyl group (SϭO) at 1022 cmϪ1 and the
CϪS stretching vibration at 756 cmϪ1 [5]
.
The complexes 1؊3 were prepared by the reaction of L
with Ln(NO3)3·nH2O or Ln(ClO4)3·nH2O in the presence
of triethyl orthoformate (see Scheme 1). The complexes are
soluble in DMF and DMSO, and slightly soluble in
CH3OH and CH3CN, but almost insoluble in H2O and ace-
tone. The IR spectrum of each complex has a νSϭO band at
around 1000 cmϪ1, which is shifted to a lower frequency
than that of the free ligand (1022 cmϪ1), indicating that the
[a]
Department of Chemistry, Nankai University, Tianjin 300071,
China
Fax: (internat.) ϩ86-22-23502458
E-mail: buxh@nankai.edu.cn
The State Key Laboratory of Rare Earth Materials Chemistry
[b]
and Applications, Peking University, Beijing 100871, China
Eur. J. Inorg. Chem. 2004, 1701Ϫ1704
DOI: 10.1002/ejic.200300751
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1701

J.-R. Li, X.-H. Bu, R.-H. Zhang
FULL PAPER
oxygen is coordinated to the LnIII ions.[5] The existence of
nitrate and perchlorate anions in the complexes was also
confirmed by the IR spectra.
Scheme 1. Schematic representation of the formation of 1؊3
Description of the Crystal Structures
Complexes 1 and 2, [Ln(L)(CH3OH)(NO3)3]n [where
Ln ϭ LaIII (1); NdIII (2)], have isostructural, neutral helical-
chain structures, with only minor differences in their ge-
ometry parameters, which reflect the normal lanthanide
contraction. The coordination environments of the LnIII
centers in 1 and 2 are shown in Figure 1 (top, with 1 as a
representative). Each LnIII center is coordinated to three
oxygen atoms of two distinct L ligands (one is mono-O and
the other is chelating), six oxygen atoms of three bidentate
nitrate groups and one oxygen atom of methanol to form a
4,4-bicapped square-antiprism geometry. Due to the small
bite angle of the nitrate group, its oxygen atoms are closer
than those of two independent L ligands, which makes their
complexes have higher coordination numbers. In 1 and 2
the smallest chelating angles of the nitrate groups are 45.25°
Figure 1. (Top) View of 1 showing the coordination environment
of the center ion, (middle) the helical-chain structures of 1 (or 2)
and (bottom) crystal packing diagram in 1 (or 2), only one position
of the disordered sets of S atoms is shown
for
1
[O(9)ϪLa(1)ϪO(7)]
and
45.07°
for
2
[O(32)ϪNd(1)ϪO(31)]. Otherwise, one relatively short and
Ϫ
˚
one longer LnϪO (NO3 ) bond [La(1)ϪO(9) ϭ 2.629(6) A
˚
and La(1)ϪO(7) ϭ 2.926(7) A for 1, Nd(1)ϪO(32) ϭ
˚
˚
2.541(6) A and Nd(1)ϪO(31) ϭ 2.947(6) A for 2] also show dihedral angle between two adjacent phenyl planes (namely,
the binding of the oxygen atoms of this nitrate group, with around one Ln center) is 66.6° for 1 and 64.5° for 2, respec-
the smaller chelating angle, to the LnIII ions. In particular, tively. The 1D helical chain is related by a 41 helical axis,
for the La(1)ϪO(7) and Nd(1)ϪO(31) bonds, the interac- which passes through the alternating LnIII ions. Further-
tions between the metal and the oxygen atom are week. The more, in the crystal packing of 1 and 2 the 1D chains are
˚
lengths of the bonds [2.436(6)Ϫ2.498(6) A for 1 and arranged parallel to each other in the a and b directions,
˚
2.365(5)Ϫ2.437(5) A for 2] between the oxygen atoms of the respectively, to form planes. However, the chains in the ad-
sulfoxide moieties and the LnIII ions are within the expected jacent planes are perpendicular to each other (see Figure 1
ranges and similar to those found in disulfoxide ana- bottom).
logues,[3f] but significantly shorter than those of the nitrate
The structure of 3 ({[La(L)(DMF)5](ClO4)3}n) consists of
groups [2.611(7)Ϫ2.926(7) A for 1 and 2.541(6)Ϫ2.958(6) A cationic, helical chains and perchlorate anions. Each chain
˚
˚
for 2] or methanol [2.553(6) A for 1 and 2.488(4) A for 2] contains the structural units [La(L)(DMF)5]3ϩ, which are
in the same complex.
˚
˚
linked by L bridges. In each [La(L)(DMF)5]3ϩ unit, the
In 1 and 2, each L links two adjacent LnIII ions to form LaIII center is coordinated to eight oxygen atoms, of which
a 1D helical chain and the shortest Ln···Ln intrachain dis- three from two distinct L ligands and five from DMF (see
tance is 11.113 A for 1 and 11.017 A for 2, as shown in Figure 2 top). The geometry of the La center approximates
Figure 1 (middle). In the chain the alternating Ln centers to a square antiprism. In 3 the LaϪO bond lengths are in
˚
˚
˚
are located in a straight line and the alternating phenyl the range of 2.4506(2)Ϫ2.5806(2) A and are in the normal
groups of the ligands are parallel to each other, while the LaϪO bond-length range of eight-coordinate LaIII com-
1702
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 1701Ϫ1704

The First (Trisulfoxide)metal Complexes
FULL PAPER
plexes. The three distances of LaϪO(L) are basically equal
In summary, three 1D lanthanide-coordination polymers
˚
and the average value is 2.4713(5) A, which is slightly longer with trisulfoxide ligands were synthesized and structurally
˚
than that in 1 [2.4573(6) A].
characterized. In the complexes, the trisulfoxide ligand
shows tridentate linkage as well as mono-O-bridging and
chelate-bridging coordination modes. Similarly to the disul-
foxide ligands, the trisulfoxide ligands also act as bridges to
link adjacent metal ions, which may allow the complexes to
have higher dimensions. To the best of our knowledge, this
is the first report on a trisulfoxide ligand used as a building
block to construct coordination polymers. This study may
not only open up a new researching domain for developing
multisulfoxide-coordination chemistry, but will also offer a
new type of organic building block for the construction of
metal-organic coordination polymers.
Experimental Section
All the reagents used for synthesis and analyses were of analytical
grade and used as received. Hydrated lanthanide nitrate and per-
chlorate were prepared from the corresponding oxides. Elemental
analyses were performed on a PerkinϪElmer 240C analyzer. IR
spectra (KBr pellets) were taken on an FT-IR 170SX (Nicolet)
spectrometer. 1H NMR spectra were measured on a Bruker AC-
P500 spectrometer (300 MHz) at 25 °C with tetramethylsilane as
the internal reference. The melting point measurement was taken
on an X-4 melting point meter.
Figure 2. (Top) View of 3 showing the coordination environment
of the center ion and (bottom) the helical-chain structure of 3, only
one position of the disordered sets of S atoms is shown
Syntheses of the Ligand: 1,3,5-Tris(bromomethyl)-2,4,6-trimeth-
ylbenzene was prepared according to a reported procedure.[7] 1,3,5-
Tris(ethylthio)-2,4,6-trimethylbenzene was synthesized by the simi-
lar literature method.[8]
In 3, the L ligands act as bridges that link adjacent metal
ions to form a helical chain (see Figure 2 bottom) with an
˚
La···La separation of 10.313 A. Within the chain, the alter-
1,3,5-Tris(ethylsulfinyl)-2,4,6-trimethylbenzene (L): L was synthe-
sized following a procedure similar to our previous work for syn-
thesizing disulfoxides.[4] Nitric acid (63 %, 2 mL) was added drop-
wise to a vigorously stirred solution of 1,3,5-tris(ethylthio)-2,4,6-
trimethylbenzene (10.3 g, 0.03 mol) in benzene (50 mL). After stir-
ring for 24 h, the resulting mixture was added to a 15 % sodium
hydrogen carbonate solution to adjust the pH value to ca. 7. The
solid product was filtered and washed with distilled water, ethanol
and diethyl ether successively. Yield 6.1 g, 52 %. M.p. 233Ϫ242 °C
(mixture of isomers). C18H30O3S3 (390.15): calcd. C 55.35, H 7.74;
found C 55.01, H 7.22. IR (cmϪ1): 2887 (w), 2546 (w), 1455 (w),
1278 (m), 1022 (s), 962 (m), 864 (m), 756 (m), 689 (m), 639 (w),
580 (w). 1H NMR (300 MHz): δ ϭ 1.40 (t, 9 H, SϪCH2ϪCH3),
2.82 (s, 9 H, PhϪCH3), 4.04 (q, 6 H, SϪCH2ϪCH3), 4.31 (s, 6 H,
SϪCH2ϪPh) ppm.
nating LaIII ions are in a straight line, as in 1 and 2, but all
the phenyl groups are parallel to each other and related by
a 21 helical axis, in contrast to 1 and 2. Another difference
is that in 3 all the chains are arranged parallel to each other
along the c axis and the perchlorate ions are located among
these chains.
In 1Ϫ3 the ligand is multidentate and displays two kinds
of coordination mode: chelate bridging and mono-O-bridg-
ing. Each L ligand uses two of the sulfinyl moieties to che-
late one LnIII center to form a 10-membered ring and uses
other one to bridge an adjacent LnIII center. In 1Ϫ3, al-
though the trisulfoxide ligand is chiral due to its three S
atoms displaying S,R,R (or S,R,S) configurations, in the
crystal the presence of a 1:1 disorder for the sulfur atom (S,
SЈ) of one of the sulfoxide moieties makes the configura-
tions offset each other, which means that the complexes as
a whole are not chiral. The SϭO bond lengths are normal
for sulfoxide moieties coordinated to metal ions and are
similar to those in di- or mono-sulfoxide analogues.[6] In
addition, and similarly to the lanthanide complexes with
disulfoxide,[3c,3d] in 1Ϫ3 there are large MϪOϪS angles
(140.1Ϫ168.8° for 1, 143.6Ϫ156.1° for 2 and 147.1Ϫ150.6°
for 3) probably due to the high coordination number of the
lanthanide ions, and the coordination configurations of the
ligands are transϪtrans (CϪSϪOϪM torsion angles are
90Ϫ270°) as those in the previously reported disulfoxide
lanthanide complexes.[3cϪ3g]
Preparation of Complexes: Caution! While we have experienced no
problems in handling LnIII perchlorates, these compounds should
be handled with great caution because of their potential for ex-
plosion.
[Ln(L)(CH3OH)(NO3)3]n [Ln ؍ La (1); Nd (2)]: Triethyl orthofor-
mate (3 mL) was added to a solution of L (117 mg, 0.3 mmol) in
CHCl3 (4 mL) and the mixture was stirred for ca. 20 min. Then
Ln(NO3)3·nH2O (0.2 mmol) in anhydrous methanol (4 mL) was ad-
ded to the above mixture and further stirred at 70Ϫ80 °C for about
4 h. The mixture was cooled to room temperature and filtered. The
filtrate was allowed to stand at room temperature for ca. one week
and single crystals suitable for X-ray analysis were obtained. For
1, yield 87 mg, 39 % based on L. C19H34LaN3O13S3 (747.58): calcd.
C 30.53, H 4.58, N 5.62; found C 30.11, H 4.27, N 5.40. IR (cmϪ1):
Eur. J. Inorg. Chem. 2004, 1701Ϫ1704
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1703

J.-R. Li, X.-H. Bu, R.-H. Zhang
M. Eddaoudi, D. B. Moler, H. Li,
FULL PAPER
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2917 (m), 2426 (w), 1636 (m), 1456 (m), 1384 (s), 1043 (m), 1001
(s), 970 (m), 839 (w), 678 (m). For 2, yield 77 mg, 34 % based on
L. C19H34NdN3O13S3 (752.91): calcd. C 30.31, H 4.55, N 5.58;
found C 30.14, H 4.21, N 5.24. IR (cmϪ1): 2941 (m), 2426 (w),
1638 (s), 1457 (m), 1384 (s), 1042 (m), 1000 (s), 970 (m), 637 (m).
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{[La(L)(DMF)5](ClO4)3}n (3): Triethyl orthoformate (2 mL) was
added to a solution of L (78 mg, 0.2 mmol) in CHCl3 (3 mL) and
the mixture was stirred for 20 min. La(ClO4)3·nH2O (0.2 mmol) in
anhydrous methanol (3 mL) was added to the mixture and a pre-
cipitate immediately appeared. The mixture was further stirred at
about 60 °C for 30 min. Then, DMF was slowly added until the
precipitate dissolved and the solution was filtered. The slow dif-
fusion of diethyl ether into the filtrate resulted in the formation of
single crystals in 23 % yield. C33H65Cl3LaN5O20S3 (1193.34): calcd.
C 33.21, H 5.49, N 5.87; found C 33.04, H 5.21, N 5.48. IR (cmϪ1):
2981 (m), 1647 (m), 1457 (w), 1384 (m), 1141 (s), 1121 (s), 1086
(m), 1001 (s), 636 (m).
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1704
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2004, 1701Ϫ1704