Tris(dithiolene) complexes of neodymium and cerium: Mononuclear species, chains, and honeycomb networks

Article abstract of DOI:10.1021/ic049055i

Reactions of Ln(BH₄)₃(THF)₃ (Ln = Nd, Ce) and M₂dddt (M = Na, K; dddt = 5,6-dihydro-1,4-dithiine-2,3- dithiolate) in THF or pyridine gave, after addition of 18c6 (18-crown-6), several crystalline compounds which all contain the tris(dithiolene) Ln(dddt)₃ unit. Crystals of [Na(18c6)(py)₂] ₂[Na(18c6)(py)][Nd(dddt)₃(py)]·3py (1·3py) are built up from discrete mononuclear cationic and anionic species whereas crystals of {[Na(18c6)(py)₂]_0.5[Na(18c6)(py) _1.5][Na_1.5Nd(dddt)₃]}_∞ (2) are composed of discrete [Na(18c6)(py)_x]⁺ cations and polymeric anionic two-dimensional layers in which the Nd(dddt)₃ units are linked to three neighbors by sodium atoms to form a honeycomb network. Analysis of the temperature dependence of the molar magnetic susceptibility of 2 shows that χ_MT decreases from 1.63 cm³ K mol ^-1 at 300 K down to 0.6 cm³ K mol^-1 at 5 K, due to the crystal-field splitting of the ⁴I_9/2 free-ion state. Complexes {[Na₃(18c6)_1.5Nd(dddt) ₃(THF)]·3THF}_∞ (3·3THF) and {[K ₃(18c6)_1.5Nd(dddt)₃(py)]·3py} _∞ (4·3py) exhibit neutral polymeric layers with the Nd(dddt)₃ units linked by M₂(18c6) fragments. In the cerium compound {[Na₂(18c6)Na(py)₂Ce(dddt) ₃(py)]·3py}_∞ (5·3py), each Ce(dddt)₃ unit is linked to two neighbors only by Na ₂(18c6) moieties, giving infinite zigzag chains.

Full text of DOI:10.1021/ic049055i

Inorg. Chem. 2005, 44, 584−593
Tris(dithiolene) Complexes of Neodymium and Cerium: Mononuclear
Species, Chains, and Honeycomb Networks
Mathieu Roger,† Th e´ r e` se Arliguie,*,† Pierre Thu e´ ry,† Marc Fourmigu e´ ,‡ and Michel Ephritikhine*,†
SerVice de Chimie Mol e´ culaire, DSM, DRECAM, CNRS URA 331, CEA/Saclay,
9
1191 Gif-sur-YVette, France, and Laboratoire de Chimie, Ing e´ ni e´ rie Mol e´ culaire et Mat e´ riaux
(CIMMA), UMR 6200 CNRSsUniVersit e´ d’Angers, 2 Bd. LaVoisier, 49045 Angers, France
Received July 16, 2004
Reactions of Ln(BH
in THF or pyridine gave, after addition of 18c6 (18-crown-6), several crystalline compounds which all contain the
tris(dithiolene) Ln(dddt) unit. Crystals of [Na(18c6)(py) [Na(18c6)(py)][Nd(dddt) (py)] 3py (1 3py) are built up from
discrete mononuclear cationic and anionic species whereas crystals of [Na(18c6)(py) 0.5[Na(18c6)(py)1.5][Na1.5
Nd(dddt) (2) are composed of discrete [Na(18c6)(py)
]+ cations and polymeric anionic two-dimensional layers
in which the Nd(dddt) units are linked to three neighbors by sodium atoms to form a honeycomb network. Analysis
of the temperature dependence of the molar magnetic susceptibility of 2 shows that
T decreases from 1.63 cm3
4 3 3 2
) (THF) (Ln ) Nd, Ce) and M dddt (M ) Na, K; dddt ) 5,6-dihydro-1,4-dithiine-2,3-dithiolate)
3
]
2 2
3
‚
‚
{
2
]
-
3
]
}
∞
x
3
ø
M
K mol- at 300 K down to 0.6 cm3 K mol- at 5 K, due to the crystal-field splitting of the 4
Complexes [Na (18c6)1.5Nd(dddt) (THF)] 3THF (3 3THF) and [K (18c6)1.5Nd(dddt) (py)] 3py
neutral polymeric layers with the Nd(dddt) units linked by M
[Na (18c6)Na(py) Ce(dddt) (py)] 3py (5 3py), each Ce(dddt) unit is linked to two neighbors only by Na
moieties, giving infinite zigzag chains.
1
1
I
}
free-ion state.
9
/
2
{
3
3
‚
}
∞
‚
{
3
3
‚
∞
(4‚
3py) exhibit
3
2
(18c6) fragments. In the cerium compound
(18c6)
{
2
2
3
‚
}
∞
‚
3
2
Introduction
(dithiolene) complexes K
2
[LnCl
3
(dmit)(phen)
2
]‚6H O (Ln )
2
La, Nd, Sm, Gd, Er, Y) which behave as insulators and were
Much attention is paid to the diversity of dithiolene
complexes of the main group and d transition metals which
exhibit interesting structures and physicochemical properties
and find applications as molecular precursors of conducting,
magnetic, and optical materials.1,2 In contrast, such complexes
of the f-elements are quite uncommon, although they seem
attractive in view of their coordination flexibility, redox
behavior, and paramagnetism which could be the source of
novel structures and electronic interactions. A very few
entries into lanthanide and actinide dithiolene compounds
transformed into typical semiconductors upon doping with
3
iodine. Baux et al. obtained a compound analyzed as Gd
2
-
(
3
tto) from the reaction of GdCl and the tetraethylammonium
4
salt of tetrathiooxalate (tto). However, none of those
complexes has been characterized by X-ray diffraction
analysis. More recently, we reported that [U(COT)(BH
COT ) η-C ) reacted with Na dddt to afford the anionic
complex [U(COT)(dddt) ] , and with the dithiocarbonates
dddtCO and dmioCO (dddtCO ) 5,6-dihydro-1,3-dithiolo-
4,5-b][1,4]dithiine-2-one, dmioCO ) 1,3,4,6-tetrathiapen-
talene-2,5-dione) to give the neutral compounds [U(cot)-
dithiolene)] and a series of Lewis base adducts of general
formula [U(COT)(dithiolene)(L) ] [dithiolene ) 5,6-dihydro-
,4-dithiine-2,3-dithiolate (dddt), 1,3-dithiole-2-one-4,5-dithi-
4 2
) ]
(
H
8 8
2
2
- 5
2
[
have been opened. Tang et al. found that addition of K
dmit ) 2-thioxo-1,3-dithiole-4,5-dithiolate) to LnCl in the
presence of 1,10-phenanthroline (phen) gave the mono-
2
dmit
(
3
(
2
n
*
To whom correspondence should be addressed. E-mail:
1
arliguie@drecam.cea.fr (T.A.); ephri@drecam.cea.fr (M.E.).
6
†
‡
olate (dmio), or 1,3-dithiole-4,5-dithiolate (mdt)]; the X-ray
crystal structures of these mono- and bis(dithiolene) orga-
CEA/Saclay.
CNRSsUniversit e´ d’Angers.
(
1) (a) Cassoux, P.; Valade, L.; Kobayashi, H.; Kobayashi, A.; Clark, R.
A.; Underhill, A. E. Coord. Chem. ReV. 1991, 110, 115. (b) Olk, R.
M.; Olk, B.; Dietzsch, W.; Kirmse, R.; Hoyer, E. Coord. Chem. ReV.
(3) Tang, Y.; Gan, X.; Tan, M.; Zheng, X. Polyhedron 1998, 17, 429.
(4) Baux, C.; Daiguebonne, C.; Guillou, O.; Boubekeur, K.; Carlier, R.;
Sorace, L.; Caneschi, A. J. Alloys Compd. 2002, 344, 114.
(5) Arliguie, T.; Fourmigu e´ , M.; Ephritikhine, M. Organometallics 2000,
19, 109.
1992, 117, 99.
(
2) Dithiolene Chemistry: Synthesis, Properties and Applications; Stiefel,
E. I., Ed.; Progress in Inorganic Chemistry, special volume, 52;
Wiley: New York, 2004.
584 Inorganic Chemistry, Vol. 44, No. 3, 2005
10.1021/ic049055i CCC: $30.25
© 2005 American Chemical Society
Published on Web 01/13/2005

Nd and Ce Tris(dithiolene) Complexes
nouranium complexes revealed the interaction between the
CdC double bond of the dithiolene ligand and the metal
center. These investigations were facilitated by our experi-
ence of the monocyclooctatetraenyl uranium compounds
which are in most cases easily identified by NMR spectros-
copy and adopt the usual four-legged piano-stool configu-
that for the Nd analogue, but with a large excess of NaBH
equiv) and by heating the reaction mixture under reflux for 35 days.
4
(10
1
H NMR (THF-d
8
, 23 °C): δ 31.6 (br, BH
(THF)1.5Nd(dddt) ]. A flask was charged with Nd(BH
(231 mg, 0.57 mmol), and THF (50 mL) was condensed
dddt (516 mg, 2.28 mmol) led to the immediate
color change of the solution, from purple to green. After stirring
for 3 days at 20 °C, a white precipitate of NaBH was deposited.
4
).
[Na
3
3
4 3
) -
(
THF)
3
in. Addition of Na
2
7
ration. After these first studies, we decided to prepare
4
homoleptic dithiolene compounds of the f-elements, expect-
ing that their high coordination numbers and fluxional
character, together with the bridging capacity of the sulfur
atoms, would lead to the creation of unpredicted and more
complicated structures which could be solved only with the
help of crystallography. The syntheses were limited to two
early members of the lanthanide series, cerium and neody-
mium, because the ionic radii of their trivalent ions are very
The solution was filtered and evaporated to dryness, leaving a green-
yellow powder. The latter was then extracted in THF (40 mL), and
1
4
some more NaBH was eliminated by filtration. From the H NMR
spectra, the green powder of [Na (THF) Nd(dddt) ] obtained after
3
1.5
3
evaporation of the solvent was contaminated with 0.5 mol equiv
of NaBH . Yield: 500 mg (99%). The difficulty in eliminating
NaBH from the powder does not permit us to rule out the formation
of an “ate” complex in the solid state. H NMR (pyridine-d
°C): δ 3.53 (s, 12H, dddt), 3.66 (m, 6H, THF), 1.62 (m, 6H, THF),
4
4
1
5
, 23
8
similar to that of uranium(III), permitting careful comparison
1
9
1.41 (q, J ) 80 Hz, 2H, NaBH
3
4
). H NMR (THF-d
.36 (s, 12H, dddt), -0.53 (q, J ) 80 Hz, 2H, NaBH
Na(18c6)(py) [Na(18c6)(py)][Nd(dddt) (py)]‚3py (1‚3py) and
[Na(18c6)(py) 0.5[Na(18c6)(py)1.5][Na1.5Nd(dddt) ]} (2). Pen-
(THF)1.5Nd(dddt)
250 mg) and 18c6 (3-10 equiv) in pyridine (5 mL). After 5 days,
8
, 23 °C): δ
of analogous 4f and 5f compounds; the possibility to obtain
4
).
a cerium(IV) derivative which could be compared with its
uranium(IV) counterpart was also attractive. Reactions of
[
2
]
2
3
{
2
]
3
∞
Ln(BH
4 3
) (THF)
3
(Ln ) Ce, Nd) and UCl
4 2
with M dddt (M
tane was carefully layered on a solution of [Na
3
3
]
)
Na, K) in the presence of 18c6 (18-crown-6) gave a variety
(
of crystalline products, from mononuclear species to two-
dimensional polymers, depending on the quantity of 18c6,
the nature of the Ln and M metals, and the solvent. Here we
report the syntheses and X-ray crystal structures of the tris-
orange crystals of 1‚3py and green crystals of 2 were deposited
together. With 3 equiv of crown ether, compound 2 was largely
predominant. Yield of hand separated crystals: 150 mg (39%). The
crystals were dried under vacuum to give a green powder of general
formula Na
3
Nd(dddt)
3 60.5
(18c6)1.5(py)2.5. Anal. Calcd for C42.5H -
(dithiolene) complexes of cerium(III) and neodymium(III),
N O S12Na Nd: C, 37.85; H, 4.52; N, 2.60. Found: C, 37.53; H,
2.5 9 3
and in the following paper, we will present the tris and
10
4.68; N, 2.58. The relative proportion of 1 was increased with the
amount of added crown ether, up to ca. 95% with 6 equiv of 18c6.
Yield of hand separated crystals: 250 mg (46%). The orange
crystals were dried under vacuum to give an orange powder of
tetrakis(dithiolene) compounds of uranium(IV).
Experimental Section
All reactions were carried out under argon (<5 ppm oxygen or
water) using standard Schlenk-vessel and vacuum-line techniques
or in a glovebox. Solvents were dried by standard methods and
distilled immediately before use. The 1H NMR spectra were
recorded on a Bruker DPX 200 instrument and referenced internally
using the residual protio solvent resonances relative to tetrame-
thylsilane (δ 0). Elemental analyses were performed by Analytische
Laboratorien at Lindlar (Germany). The crystalline compounds are
sensitive to the thermal dissociation of lattice solvent, and so, the
experimentally determined elemental analyses are often found to
be lower than the computed analyses.
general formula Na
3
Nd(dddt)
3 3
(18c6) (py)4.5. Anal. Calcd for
70.5 106.5 4.5 18 3
C H N O S12Na Nd: C, 44.49; H, 5.64; N, 3.31; S, 20.22.
1
Found: C, 43.16; H, 5.57; N, 3.65; S, 19.00. H NMR of 1‚3py
pyridine-d , -35 °C): δ 3.39 (s, 12H, dddt), 3.20 (s, 72H, 18c6).
H NMR of 2 (pyridine-d , 23 °C): δ 4.09 (s, 12H, dddt), 3.44 (s,
6H, 18c6).
[Na (18c6)1.5Nd(dddt)
was carefully layered on a solution of [Na
(
1
5
5
3
{
3
3
(THF)]‚3THF}
(THF)1.5Nd(dddt)
mg) and 10 mol equiv of 18c6 (18 mg) in THF (0.5 mL). After
-10 days, few green crystals of 3‚3THF were deposited together
∞
(3‚3THF). Pentane
3
3
] (ca
6
5
with a sticky off-white powder; crystals of suitable quality could
not be obtained in sufficient quantity for chemical analyses.
Syntheses. The precursors Nd(BH
dddt12 were prepared by published methods; Ce(BH
synthesized in 72% yield from CeCl using a procedure similar to
4 3
) (THF)
3
,11 Na
2
dddt, and K
2
-
4
)
3
(THF) was
3
3
{[K (18c6)1.5Nd(dddt)
3
(py)]‚3py}
∞
(4‚3py). A flask was charged
dddt (820 mg, 3.17
3
with Nd(BH
4 3
)
(THF) (414 mg, 1.02 mmol), K
3
2
mmol), and 18c6 (865 mg, 3.27 mmol), and pyridine (60 mL) was
condensed in. After stirring for 3 days at 20 °C, the green precipitate
was filtered off, washed with pyridine, and dried under vacuum.
This powder was insoluble in pyridine unless more than 3 mol equiv
of 18c6 was added, and the H NMR spectrum showed the presence
4
of KBH (ca. 1.3 equiv). The borohydride was eliminated by
successive extractions with pyridine in the presence of 18c6. Thus,
the green powder (1200 mg) was stirred for 2 days in a solution of
the crown ether (200 mg) in pyridine (30 mL), filtered off, and
dried under vacuum; this operation was repeated twice for complete
(
6) (a) Arliguie, T.; Thu e´ ry, P.; Fourmigu e´ , M.; Ephritikhine, M. Orga-
nometallics 2003, 22, 3000. (b) Arliguie, T.; Thu e´ ry, P.; Fourmigu e´ ,
M.; Ephritikhine, M. Eur. J. Inorg. Chem. 2004, 4502.
(
7) (a) Leverd, P. C.; Arliguie, T.; Lance, M.; Nierlich, M.; Vigner, J.;
Ephritikhine, M. J. Chem. Soc., Dalton Trans. 1994, 501. (b) Boisson,
C.; Berthet, J. C.; Lance, M.; Vigner, J.; Nierlich, M.; Ephritikhine,
M. J. Chem. Soc., Dalton Trans. 1996, 947. (c) Arliguie, T.; Baudry,
D.; Berthet, J. C.; Ephritikhine, M.; Mar e´ chal, J. F. New J. Chem.
1
1991, 15, 569.
(
8) Shannon, R. D. Acta Crystallogr., Sect. A 1976, 32, 751.
(9) (a) Berthet, J. C.; Nierlich, M.; Ephritikhine, M. Polyhedron 2003,
2
2, 3475. (b) Berthet, J. C.; Miquel, Y.; Iveson, P. B.; Nierlich, M.;
Thu e´ ry, P.; Madic, C.; Ephritikhine, M. J. Chem. Soc., Dalton Trans.
002, 3265.
4
removal of KBH . The resulting green powder (808 mg, 53%) was
2
(
(
(
10) See the following article in this issue: Roger, M.; Arliguie, T.; Thu e´ ry,
P.; Fourmigu e´ , M.; Ephritikhine, M. Inorg Chem. 2005, 44, 594-600.
11) Cendrowski-Guillaume, S. M.; Le Gland, G.; Nierlich, M.; Ephri-
tikhine, M. Organometallics 2000, 19, 5654.
12) Guyon, F.; Lenoir, C.; Fourmigu e´ , M.; Larsen, J.; Amaudrut, J. Bull.
Soc. Chim. Fr. 1994, 131, 217.
dissolved in pyridine (60 mL) in the presence of 18c6 (400 mg).
Slow diffusion of pentane into this solution led to the formation of
green crystals of 4‚3py. Yield: 240 mg (36%). The crystals were
dried under vacuum to give a green powder of general formula
3 3 55.5 1.5 9 12 3
K Nd(dddt) (18c6)1.5(py)1.5. Anal. Calcd for C37.5H N O S K -
Inorganic Chemistry, Vol. 44, No. 3, 2005 585

Roger et al.
Nd: C, 34.18; H, 4.24; N, 1.60; S, 29.20. Found: C, 33.36; H,
.66; N, 1.77; S, 28.90. The crystals are insoluble in pyridine,
precluding NMR spectra to be recorded.
[Na (18c6)Na(py) Ce(dddt) (py)]‚3py}
charged with Ce(BH (THF) (436 mg, 1.09 mmol), and THF (50
mL) was condensed in. The colorless solution immediately turned
yellow upon addition of Na dddt (856 mg, 3.78 mmol). After
stirring for 12 h at 20 °C, the solution was filtered, and addition of
8c6 (858 mg, 3.25 mmol) led to the precipitation of a yellow
powder which was filtered off, washed with THF (100 mL), and
dried under vacuum. The powder was contaminated with 0.5 equiv
4 4
of NaBH . The difficulty in eliminating NaBH from the powder
does not permit us to rule out the formation of an “ate” complex
in the solid state. Yield: 1265 mg (85%). Slow diffusion of pentane
into a pyridine solution of this powder afforded yellow crystals of
whereas all other atoms in these moieties had to be refined with
restraints on bond lengths and displacement parameters. The highest
residual electron density peak in this compound is located near a
carbon atom of the badly resolved crown ether moiety. Some short
H‚‚‚H contacts involving the protons of badly behaving solvent or
crown ether moieties in compounds 3‚3THF and 5‚3py are likely
due to the imperfect description of the disordered nature of these
molecules.
Compound 4‚3py was found to undergo a temperature-dependent
phase transition: the triclinic phase present at 100 K is replaced
by a trigonal phase at room temperature (293 K). In the latter, the
Nd atom is located on the 3-fold axis, and the three dddt ligands
and three potassium ions are symmetry-related. As a consequence,
the pyridine bound to Nd is disordered over three positions at 60°
from each other. No other important variation of the structure is
observed. This phase transition is thus an order/disorder one,
between a low-temperature low-symmetry phase and a high-
temperature high-symmetry disordered one. Determination of the
unit cell at different temperatures indicates that the transition occurs
at approximately 260-270 K. Due to extended disorder, the room
temperature structure could not be properly refined. Crystal data
4
{
2
2
3
∞
(5‚3py). A flask was
4
)
3
3
2
1
5
‚3py. Yield 250 mg (20%). The crystals were dried under vacuum
to give a yellow powder of general formula Na Ce(dddt) (18c6)-
py) . Anal. Calcd for C34 Ce: C, 34.82; H, 3.95;
N, 2.39; S, 32.82. Found: C, 34.59; H, 4.11; N, 2.58; S, 33.07. H
NMR (pyridine-d , 23 °C): δ 3.21 (s, 12H, dddt), 3.32 (s, 24H,
8c6).
Crystallographic Data Collection and Structure Determina-
3
3
(
2
46 2 6 3
H N O S12Na
1
5
1
68 3 4 9
of the high-symmetry phase: C50H K N NdO S12, M ) 1515.34,
trigonal, space group P 3h , a ) b ) 19.4602(17) Å, c ) 10.3386(4)
tion. The data were collected at 100(2) K on a Nonius Kappa-
CCD area detector diffractometer13 using graphite-monochromated
Mo KR radiation (λ ) 0.71073 Å). The crystals were introduced
in glass capillaries with a protecting “Paratone-N” oil (Hampton
Research) coating. The unit cell parameters were determined from
3
Å, R ) â ) 90°, γ ) 120°, V ) 3390.7(4) Å , Z ) 2, D ) 1.484
g cm , µ ) 1.370 mm , F(000) ) 1554.
c
-
3
-1
All non-hydrogen atoms were refined with anisotropic displace-
ment parameters (except the disordered ones in 2) with some
restraints on bond lengths and/or displacement parameters for some
disordered or badly behaving atoms, as indicated above. Hydrogen
atoms were introduced at calculated positions, except in disordered
parts for compounds 2-5‚3py, and were treated as riding atoms
with a displacement parameter equal to 1.2 times that of the parent
atom. Crystal data and structure refinement details are given in
10 frames, then refined on all data. A 180° æ-range was scanned
with 2° steps during data collection. The data were processed with
DENZO-SMN.14 The structures were solved by direct methods (1‚
3py and 2) or by Patterson map interpretation (3‚3THF-5‚3py)
with SHELXS-97 and subsequent Fourier-difference synthesis and
refined by full-matrix least-squares on F2 with SHELXL-97.
15
1
8
Table 1. The molecular plots were drawn with SHELXTL and
ORTEP-3/POV-Ray.19
Absorption effects were corrected empirically with the program
DELABS from PLATON.16 The correct enantiomorph in 1‚3py was
determined from the value of the Flack parameter [-0.018(12)].17
Magnetic Measurements. Temperature dependence of the molar
magnetic susceptibility of 2 was determined on a 40 mg polycrys-
talline sample at 3000 G using a Quantum Design SQUID
magnetometer MPMS-5 in the 5-300 K range. The data were
corrected for the sample holder and for the diamagnetic contribution
Despite different alkali metal ions and solvent molecules, com-
pounds 3‚3THF and 4‚3py crystallize in the same space group, with
very similar unit cell parameters.
Some disorder on counterions or solvent molecules is present,
in greater or lesser extent, in all these structures. In compound 2,
one of the pyridine molecules bound to Na(4) [containing atom
N(2)] is disordered over two positions related by the symmetry
center, which are very close to each other, one of them bound to
Na(4) and the other to Na(4′) [the latter related to Na(4) by the
symmetry center]; since both positions cannot be occupied simul-
taneously, this pyridine molecule has been affected with a 0.5
occupancy parameter. Three pyridine molecules in 4‚3py and two
in 5‚3py are disordered over two positions which were refined with
occupancy parameters constrained to sum to unity. In compounds
-
6
3
-1
evaluated at 600 × 10 cm mol
.
Results and Discussion
Syntheses. We first tried to prepare lanthanide dithiolene
complexes by treating the chlorides NdCl and CeCl with
3
3
the sodium salt of the dddt anion in THF, but no reaction
was observed, even at 65 °C, certainly because of the
insolubility of the reactants. We then used the borohydrides
M(BH
valuable precursors of various organometallic derivatives.
Reaction of Nd(BH (THF) with a slight excess of Na
4
)
3
(THF)
3
(M ) Nd, Ce) which were shown to be
1
2
1
1‚3py, 4‚3py, and 5‚3py, some pyridine solvent molecules were
)
4 3
3
-
further refined as idealized hexagons. In 3‚3THF, the disorder
affecting one crown ether and the three solvent THF molecules
could only be partly solved; one carbon atom of the crown ether
and two from a THF molecule were found to be disordered over
two positions which have been attributed a 0.5 occupancy factor
dddt in THF gave, after filtration of the solution and
evaporation to dryness, the tris(dithiolene) compound
[Na
3 3
(THF)1.5Nd(dddt) ] which was isolated as a green
powder in almost quantitative yield but was contaminated
1
with ca. 0.5 mol equiv of NaBH
4
. The H NMR spectra in
(13) Kappa-CCD Software; Nonius B.V.: Delft, The Netherlands, 1998.
(14) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307.
(15) Sheldrick, G. M. SHELXS-97 and SHELXL-97; University of G o¨ ttin-
gen: G o¨ ttingen, Germany, 1997.
THF-d or pyridine-d show a singlet at δ 3.36 or 3.53,
respectively, attributed to magnetically equivalent dddt
8
5
(
16) Spek, A. L. PLATON; University of Utrecht: Utrecht, The Netherlands,
(18) Sheldrick, G. M. SHELXTL, version 5.1; Bruker AXS Inc.: Madison,
WI, 1999.
2000.
(17) Flack, H. D. Acta Crystallogr., Sect. A 1983, 39, 876.
(19) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
586 Inorganic Chemistry, Vol. 44, No. 3, 2005

Nd and Ce Tris(dithiolene) Complexes
Table 1. Crystal Data and Structure Refinement Details for Complexes 1-5
1‚3py
2
3‚3THF
4‚3py
5‚3py
empirical formula
C93H129N9-
Na3NdO18S12
2258.98
monoclinic
P21
13.8785(13)
24.3573(13)
16.9363(17)
90
110.288(4)
90
5370.0(8)
2
1.397
0.795
2358
C42.5H60.5N2.5-
Na3NdO9S12
1348.36
triclinic
P1h
14.2753(9)
14.8237(7)
17.0518(10)
114.415(3)
91.860(3)
116.398(3)
2837.8(3)
2
C46H80Na3-
NdO13S12
1439.03
triclinic
P1h
10.1439(8)
18.4818(11)
19.2305(15)
118.159(4)
92.238(4)
94.281(4)
3158.4(4)
2
C50H68K3N4-
NdO9S12
1515.34
triclinic
P1h
10.3168(5)
18.6713(14)
19.3117(15)
118.759(3)
90.469(4)
92.869(4)
3254.8(4)
2
C54H66CeN6-
Na3O6S12
1488.94
triclinic
P1h
12.1362(11)
16.705(2)
17.7897(16)
74.203(6)
74.938(7)
73.106(6)
3256.0(6)
2
M/g mol-
cryst syst
space group
a/Å
1
b/Å
c/Å
R/deg
â/deg
γ/deg
3
V/Å
Z
-
3
Dcalc/g cm
1.578
1.431
1380
1.513
1.294
1490
1.546
1.427
1554
1.519
1.155
1526
-
1
µ(Mo KR)/mm
F(000)
reflns collected
indep reflns
obsd reflns [I > 2σ(I)]
Rint
36715
19752
12156
0.107
19776
9993
7138
0.066
21654
10947
7873
0.078
22537
11415
8587
0.059
22290
11412
7527
0.076
params refined
1221
634
703
758
779
R1
0.069
0.059
0.074
0.044
0.061
wR2
0.170
0.146
0.194
0.107
0.153
S
∆
∆
0.975
-1.01
0.76
1.035
-0.72
1.22
1.063
-1.28
1.53
1.033
-0.61
0.60
1.015
-0.95
1.10
Fmin/e Å-
3
-
3
Fmax/e Å
Scheme 1. Synthesis of the Tris(dithiolene) Lanthanide Complexes
and Representation of the Environment of the Ln(dddt)3 Units
4
ligands, in addition to the signals of THF and NaBH . No
crystals were deposited from pyridine or THF solutions of
the green powder which presumably contain mixtures of
soluble “ate” complexes in which the alkali metal ions are
scrambling over the dithiolene sulfur atoms; for inducing
crystallization of more rigid compounds, variable amounts
of 18c6, from 3 to 10 mol equiv with respect to neodymium,
were added to these solutions. Three products were thus
3
obtained, containing the Nd(dddt) moiety in distinct forms
which are represented in Scheme 1. Slow diffusion of pentane
into the pyridine solutions led to the formation of orange
and green crystals together; the relative proportion of the
orange crystals was found to increase with the amount of
added crown ether (ca 95% with 6 equiv of 18c6). X-ray
diffraction analysis revealed that the orange crystals of the
pyridine solvate [Na(18c6)(py)
py)]‚3py (1‚3py) are composed of discrete mononuclear
cationic and anionic species, whereas the green crystals of
2 2 3
] [Na(18c6)(py)][Nd(dddt) -
(
{
[Na(18c6)(py)
2
]
0.5[Na(18c6)(py)1.5][Na1.5Nd(dddt)
3
]}
∞
(2)
+
are built up from discrete [Na(18c6)(py)
infinite anionic 2D layers in which the Nd(dddt)
x
]
cations and
units are
3
linked to three neighbors by Na atoms in an hexagonal
network.
Only green crystals were deposited in small quantity from
solutions of [Na (THF)1.5Nd(dddt) ] in THF, after addition
3 3
of 10 mol equiv of 18c6. Their structure is quite distinct
from that of 2 since it exhibits neutral polymeric layers of
composition {[Na (18c6)1.5Nd(dddt) (THF)]} (3); the major
3 3 ∞
difference between the crystal structures of 2 and 3‚3THF
is that the latter does not contain separated cationic sodium
dddt. The same mixture in pyridine gave a green powder
which was soluble in this solvent only after addition of more
than 3 mol equiv of crown ether. Green crystals of
{[K (18c6) Nd(dddt) (py)]‚3py} (4‚3py) were formed upon
slow diffusion of pentane into this pyridine solution,
whatever the quantity of added 18c6, between 3 and 10 mol
equiv. The structure of 4‚3py is remarkably quite identical
species, the Nd(dddt)
fragments in place of single Na atoms.
The potassium salt of the dddt anion did not react with
Nd(BH (THF) in THF, even in the presence of 18c6; this
lack of reactivity can be attributed to the insolubility of K
3 2
moieties being linked by Na (18c6)
3
1.5
3
∞
4
)
3
3
2
-
Inorganic Chemistry, Vol. 44, No. 3, 2005 587

Roger et al.
to that of 3‚3THF, the THF molecules having been replaced
with pyridine molecules and the Na atoms with K atoms.
4 3 3 2
Treatment of Ce(BH ) (THF) with Na dddt in THF
afforded, after addition of 3-10 mol equiv of 18c6, a yellow-
green powder which was recrystallized in a mixture of
pyridine and pentane to give yellow crystals of composition
{
[Na
sist of infinite zigzag chains in which the Ce(dddt)
are linked to two neighbors by Na (18c6) fragments.
The variety of structures for complexes 1-5 isolated from
reactions of Ln(BH (THF) (Ln ) Ce, Nd) and M dddt
M ) Na, K) in pyridine or THF in the presence of 18c6,
which all contain the Ln(dddt) moiety, results from the
2
(18c6)Na(py)
2
Ce(dddt)
3
(py)]‚3py}
∞
(5‚3py); these con-
3
units
2
4
)
3
3
2
(
Figure 1. View of the [Nd(dddt)3(py)]3 anion in 1‚3py. The hydrogen
atoms have been omitted for clarity. Displacement ellipsoids are drawn at
the 50% probability level.
-
3
diverse and competitive modes of complexation of the alkali
metal ions with the sulfur atoms of the dddt ligands, the
oxygen atoms of the crown ether, and the nitrogen atoms of
the pyridine solvent. It is only in pyridine that the sodium
ions were inserted into the crown ether to give separated
+
[Na(18c6)(py)
x
] ions in 1 and 2; the relative proportions of
+
these complexes, that is the number of [Na(18c6)(py)
x
] ions
which are formed, are easily explained by the quantity of
added crown ether. That the solvent plays an important role
in the synthesis of these compounds is illustrated by the
formation of 3‚3THF instead of 2 when pyridine was
replaced with THF; in that case, dissociation into cationic
and anionic species did not occur. One could imagine that 2
3 3 ∞
would be in equilibrium with {[Na (18c6)1.5Nd(dddt) (py)]} ,
the analogous complex of 3 in pyridine (or the sodium
analogue of 4), following reversible insertion of [Na(18c6)]+
into Na-S bonds of the anionic layer. However, this insertion
was not evidenced by increasing the concentration of the
solution from 0.01 to 0.15 M, since only the green crystals
of 2 were invariably formed and the analogous complex of
3
was not obtained in pyridine. The nature of the alkali and
lanthanide metals has also a great influence on the structure
of the products, as shown by the synthesis of 4 or 5 instead
of 2 when K
2
dddt or Ce(BH (THF)
4
)
3
3
was used in place of
Na dddt or Nd(BH
2
4
)
3
(THF) , respectively. The different
3
factors which may contribute to the unpredicted building of
compounds 1-5, in particular the coordinating ability of the
solvent and the ligands, the ionic radii of the metals, and
the solubility of the products, are difficult to rationalize;
nevertheless, the serendipitous syntheses of the complexes
were reproducible.
Figure 2. (a) View of the anionic fragment [Na1.5Nd(dddt)3]1 in 2. The
hydrogen atoms have been omitted for clarity. Displacement ellipsoids are
drawn at the 50% probability level. Symmetry codes: ′ ) -x, -y, 1 - z;
′′ ) 1 - x, -y, 1 - z; ′′′ ) 1 - x, 1 - y, 1 - z. (b) View of the honeycomb
arrangement in compound 2. Counterions have been omitted.
.5-
Crystal Structures. Views of the separated anion
3
-
[
Nd(dddt)
3
]1
(py)] in 1‚3py, the anionic fragment [Na1.5
-
.5-
Nd(dddt)
3
in 2, and the neutral units [Na
(18c6) Na(py)
py)] in 5‚3py are shown in Figures 1-4, respectively; the
3
(18c6)
3
Nd-
(dddt)
3
(THF)] in 3‚3THF and [Na
2
2
2
Ce(dddt) -
3
trary;20 one can see the Nd atom in a very distorted square-
capped trigonal prismatic configuration, the trigonal faces
of the prism being defined either by the S(1A), S(2A), S(1B)
and S(1C), S(2B), S(2C) atoms or S(1A), S(1C), S(2C) and
S(1B), S(2B), N(1) atoms with N(1) or S(2A) in capping
positions. Such a geometry was found in the â-diketonate
(
structure of 4‚3py resembles that of 3‚3THF, as outlined in
Scheme 1. Selected bond distances and angles are listed in
Table 2.
In all the complexes, except 2, an extra THF or pyridine
molecule is coordinated to the Ln(dddt)
observed in compounds of general formula [M(bidentate
ligand) (unidentate ligand)], the polyhedron chosen to de-
scribe best the metal environment in 1 is somewhat arbi-
3
fragment. As often
2
1
3 2
complexes [Yb(MeCOCHCOMe) (H O)] and [Lu(Bu-
3
(
20) Kepert, K. L. Inorganic Stereochemistry; Springer-Verlag: Berlin,
1982.
588 Inorganic Chemistry, Vol. 44, No. 3, 2005

Nd and Ce Tris(dithiolene) Complexes
Figure 4. (a) View of the neutral unit [Na2(18c6)Na(py)2Ce(dddt)3(py)]
in 5‚3py. The hydrogen atoms have been omitted for clarity. Displacement
ellipsoids are drawn at the 30% probability level. (b) View of the zigzag
chain arrangement in compound 5. Only one component of the disordered
pyridine molecule [containing N(3)] is represented. Solvent molecules have
been omitted.
Complex 2 is the sole true homoleptic tris(dithiolene)
lanthanide compound, and it is interesting to compare its
structure with those of the d transition metal analogues. The
latter have attracted much attention because they were found
to adopt in many cases a near trigonal prismatic coordination
Figure 3. (a) View of the neutral unit [Na3(18c6)1.5Nd(dddt)3(THF)] in
3
‚3THF. The hydrogen atoms have been omitted for clarity. Displacement
ellipsoids are drawn at the 30% probability level. (b) View of the honeycomb
arrangement in compound 3. Only one component of the disordered part
of one crown ether is represented. Solvent molecules have been omitted.
geometry while the majority of all six-coordinate complexes
25-27
exhibit an octahedral geometry.
These distortions away
from the octahedron toward the trigonal prism have been
explained by interligand bonding interactions within the S
2
2
3 5 4
COCHCOBu) (NC H Me)]. In contrast, the six sulfur atoms
3
and the nitrogen or oxygen atom in complexes 3 and 4 clearly
define a capped octahedron with O(1) or N(1) in the unique
capping position, the Nd-O(1) or Nd-N(1) line being a
pseudo-3-fold axis of symmetry (Figure 5); this stereochem-
istry is the only one which renders the three bidentate ligands
equivalent.2 The two triangles S(1A)-S(1B)-S(1C) and
S(2A)-S(2B)-S(2C) are nearly equilateral, in almost per-
fectly staggered conformation, and their dihedral angle is
equal to 0.22(2)° and 2.29(1)° in 3 and 4, respectively. The
triangles and by optimum overlap between the sulfur π
26
orbitals and the metal d orbitals. The structure of 2 does
not depart from this trend since the six S atoms are at the
vertices of a distorted trigonal prism around the metal center
(Figure 6). The two nearly equilateral triangles S(1A)-
0
S(1B)-S(1C) and S(2A)-S(2B)-S(2C) are almost parallel,
with a dihedral angle of 1.87(6)°, and are twisted from their
eclipsed conformation by an angle of ca. 20°. The neody-
mium atom is located between these planes at a distance of
1.7515(11) and 1.4867(11) Å, respectively. The coordination
geometry of 2 is similar to that found in the tris(dithiophos-
Nd atom which lies inside the S
S(1) than to the S(2) plane, at distances of 0.5747(18) and
.9220(17) Å in 3, and 0.6454(7) and 1.9244(7) Å in 4. The
6
octahedron is closer to the
3
3
1
phinate) complexes [Ln(S
but is different from that of the homoleptic thiolate com-
2 2 3
PCy )
] (Ln ) Pr, Sm, Dy, Lu)28
cerium atom in 5 exhibits the same capped octahedral
coordination geometry, but slightly more distorted, the
(
23) Cotton, F. A.; Legzdins, P. Inorg. Chem. 1968, 7, 1777.
dihedral angle between the S(1)
3 3
and S(2) triangles being
(24) Zalkin, A.; Templeton, D. H.; Karraker, D. G. Inorg. Chem. 1969, 8,
2
680.
equal to 6.92(6)°. This stereochemistry is also that adopted
(
25) (a) McCleverty, J. A. Prog. Inorg. Chem. 1968, 10, 49. (b) Eisenberg,
23
by the â-diketonate complexes [Y(PhCOCHCOMe)
3 2
(H O)]
R. Prog. Inorg. Chem. 1970, 12, 295.
and [Ho(PhCOCHCOPh) (H
3
2
O)].24
(26) (a) Stiefel, E. I.; Eisenberg, R.; Rosenberg, R. C.; Gray, H. B. J. Am.
Chem. Soc. 1966, 88, 2956. (b) Schrauzer, G. N.; Mayweg, V. P. J.
Am. Chem. Soc. 1966, 88, 3235. (c) Bennett, M. J.; Cowie, M.; Martin,
J. L.; Takats, J. J. Am. Chem. Soc. 1973, 95, 7504. (d) Martin, J. L.;
Takats, J. Inorg. Chem. 1975, 14, 1358.
(21) Cunningham, J. A.; Sands, D. E.; Wagner, W. F.; Richardson, M. F.
Inorg. Chem. 1969, 8, 22.
(
22) Wasson, S. J. S.; Sands, D. E.; Wagner, R. F. Inorg. Chem. 1973, 12,
(27) Beswick, C. L.; Schulman, J. M.; Stiefel, E. I. Prog. Inorg. Chem.
2004, 52, 55.
187.
Inorganic Chemistry, Vol. 44, No. 3, 2005 589

Roger et al.
Table 2. Selected Bond Distances (Å) and Angles (deg) for Complexes
-5
1
1
‚3py
2
3‚3THF
4‚3py
5‚3py
Ln-S(1A)
2.817(2) 2.8292(18) 2.874(2) 2.8780(12) 2.922(2)
2.861(2) 2.8819(19) 2.906(2) 2.8989(12) 2.8944(17)
2.872(3) 2.8469(19) 2.871(2) 2.8435(12) 2.9303(18)
2.869(2) 2.8748(18) 2.899(2) 2.9109(12) 2.9567(18)
2.870(3) 2.8347(19) 2.881(2) 2.9053(13) 2.9168(18)
2.853(3) 2.8710(19) 2.883(2) 2.9421(12) 2.9136(19)
Ln-S(2A)
Ln-S(1B)
Ln-S(2B)
Ln-S(1C)
Ln-S(2C)
Ln-N(1) or
2.658(7)
2.553(6) 2.695(4)
2.717(6)
Nd-O(1)
Ln-C(1A)
Ln-C(2A)
Ln-C(1B)
Ln-C(2B)
Ln-C(1C)
Ln-C(2C)
M(1)-S(1A)
M(1)-S(2A)
M(2)-S(1B)
M(2)-S(2B)
M(3)-S(1C)
M(3)-S(2C)
Na(1)-S(4C)
Na(2)-S(4A)
Na(3)-S(4B)
M(1)-S(2B)
M(2)-S(2C)
M(3)-S(2A)
2.928(7)
2.946(7)
2.897(7)
2.910(7)
2.881(7)
2.933(7)
3.051(9) 3.088(4)
3.082(8) 3.087(4)
3.243(9) 2.996(5)
3.208(9) 3.013(5)
3.090(8) 3.338(5)
3.101(8) 3.325(5)
3.037(7)
3.041(7)
3.260(7)
3.221(7)
3.102(7)
3.083(7)
Figure 6. Metal environment in 2. Displacement ellipsoids are drawn at
the 50% probability level. The distorted trigonal prism is shown as black
lines.
2.7968(19) 2.892(4) 3.1293(15) 2.934(3)
2.8629(18) 3.168(4) 3.2830(16) 2.762(3)
2.8469(18) 2.966(4) 3.2407(15) 3.025(3)
2.9480(19) 3.153(4) 3.3011(16) 2.995(3)
2.9126(19) 2.919(4) 3.2318(15) 2.927(3)
2.9439(19) 3.063(4) 3.2463(16) 3.071(3)
3.446(2)
to 2.86(2) Å in 2 and reflects, with respect to 3 and 4, the
lower coordination number of the complex. The mean
metal-sulfur bond length of 2.92(2) Å in 5 is 0.02-0.03 Å
longer than in 3 and 4, in agreement with the variation in
3.0675(19)
3.090(2)
8
the ionic radii of the trivalent Nd and Ce ions. These bond
lengths can be compared with those of 2.93(1) Å in [Nd-
2.915(4) 3.2386(16) 2.786(3)
2.958(4) 3.2023(16) 2.878(3)
2.958(4) 3.1504(16) 2.829(4)
3
0
(C
5
H
4
Me)
)} (µ-S Bu)
and 3.02(2) Å for the bridging thiolate ligands in [Ce(SC
2
(µ-SPh)(THF)]
2
,
2
2.91(3) Å in [Na(THF) {Nd-
t
11
t
i
31
(C
8
H
8
2
3
], 2.88(1) Å in [Ce(C
H
5 4
2 2
Bu) (µ-S Pr)] ,
S(1A)-Ln-S(2A) 72.23(7) 71.43(5)
S(1B)-Ln-S(2B) 71.64(10) 71.47(5)
S(1C)-Ln-S(2C) 71.30(7) 71.75(5)
70.34(6) 69.41(3)
70.51(6) 70.93(3)
69.98(6) 69.73(3)
68.95(5)
68.45(5)
69.28(5)
6 5 2
F ) -
3
2
6 5 3 2
(µ-SC F )(THF) ] . In line with the increase of the M-S
a
bond lengths from 1 to 5, the chelate bite angles S-Ln-S
slightly decrease with average values of 71.7(4)° in 1, 71.6-
θ
A
θ
B
θ
C
22.77(12) 85.06(4)
8.35(14) 87.81(5)
13.53(12) 87.33(6)
78.95(7) 77.85(3)
69.08(7) 80.74(4)
77.57(6) 65.84(4)
82.34(5)
72.73(6)
79.22(5)
(1)° in 2, 70.3(2)° in 3, 70.0(7)° in 4, and 68.9(3)° in 5.
a
θA, θB, and θC are the folding angles of the dddt ligands A, B, and C,
The S fragment of the dddt ligands is planar with an
4 2
C
respectively.
rms deviation of 0.01-0.07 Å and forms a dihedral angle θ
with the corresponding S-Ln-S plane. The average value
of θ in 2, 86.7(12)°, is ca. 10° larger than in 3-5, likely
reflecting the lower coordination number of the metal which
facilitates the folding of the ligand. However, the folding θ
angles in 1 are much smaller than in 3-5; this difference
can be explained by the greater electron density on the metal
which weakens the interaction between an empty metal
12,33
orbital and the HOMO of the dithiolene ligand.
The large
folding of the dddt ligands in compounds 2-5 brings the
C(1) and C(2) atoms in close contact with the metal center,
at an average distance of 2.92(2), 3.13(7), 3.14(14), and 3.12-
(9) Å, respectively. These values can be compared with the
mean metal-carbon bond lengths in the neodymium arene
Figure 5. Metal environment in 4‚3py. Displacement ellipsoids are drawn
at the 50% probability level. The distorted octahedron is shown as black
lines.
34
complexes [Nd(C
Ph -2,6) ] [3.04(8) Å], and with the contacts of 2.83(3)-
.23(4) Å between the neodymium and the ortho and meta
carbon atoms of two phenyl rings of the tetraphenylborate
6 6 4 3 6 3
H )(AlCl ) ] [2.93(2) Å] and [Nd(OC H -
3
5
2
3
3
t
pounds [Li(tmeda)]
3
[Ln(S Bu)
6
] (Ln ) Sm, Yb) which adopt
an octahedral configuration.2
9
5 5 2 4
Me ) ][BPh ]. In all the complexes 1-5,
36
anion in [Nd(C
the characteristics of the dithiolene ligands, i.e., the average
The average Nd-S distance in 1, 2.86(2) Å, is only slightly
shorter than that of 2.886(13) or 2.90(3) Å in 3 and 4,
respectively; this difference is smaller than that expected for
terminal and bridging SR groups, ca. 0.2 Å, and can be
accounted for by the more important electron density on the
metal center of 1. The average Nd-S distance is also equal
(
(
(
(
30) Shen, Q.; Li, H.; Yao, C.; Yao, Y.; Zhang, L.; Yu, K. Organometallics
2001, 20, 3070.
31) Stults, S. D.; Andersen, R. A.; Zalkin, A. Organometallics 1990, 9,
1623.
32) Melman, J. H.; Rohde, C.; Emge, T. J.; Brennan, J. G. Inorg. Chem.
2002, 41, 28.
33) Lauher, J. W.; Hoffman, R. J. Am. Chem. Soc. 1976, 98, 1729.
(
28) (a) Meseri, Y.; Pinkerton, A. A.; Chapuis, G. J. Chem. Soc., Dalton
Trans. 1977, 725. (b) Pinkerton, A. A.; Scharzenbach, D. J. Chem.
Soc., Dalton Trans. 1980, 1300.
(34) Fan, B.; Shen, Q.; Lin, Y. J. Organomet. Chem. 1989, 377, 51.
(35) Deacon, G. B.; Feng, T.; Skelton, B. W.; White, A. H. Aust. J. Chem.
1995, 48, 741.
(29) Tatsumi, K.; Amemiya, T.; Kawaguchi, H.; Tani, K. J. Chem. Soc.,
Chem. Commun. 1993, 773.
(36) Evans, W. J.; Seibel, C. A.; Ziller, J. W. J. Am. Chem. Soc. 1998,
120, 6745.
590 Inorganic Chemistry, Vol. 44, No. 3, 2005

Nd and Ce Tris(dithiolene) Complexes
2
C(sp )sS and CdC distances of 1.76(3)-1.774(6) Å and
Na(1)-N(3) bond lengths in 5, 2.552(7) and 2.404(6) Å, are
1
.355(7)-1.37(2) Å are consistent with those found in [Mo-
unexceptional; they are, for example, similar to those of 2.46-
(dddt)] [1.76(1) and 1.33(1) Å]37 and [Na(18c6)-
41
(C
5 5
H )
2
(1) and 2.50(1) Å in [Sm(SePh)(py)
2
3 2 2
(µ-SePh) Na(py) ] ,
5
+
42
(THF)][U(C
8 8 2
H )(dddt) ] [1.75(1) and 1.36(1) Å], indicating
and 2.56(2) Å in the [Na(py)
6
] cation. The average Na-
that the dithiolate ligand is effectively in its dianionic form.
With the exception of 1, the Ln(dddt) units are surrounded
by three sodium or potassium atoms which form a nearly
equilateral triangle, almost parallel to the S(1) and S(2)
triangles, with a pseudo-3-fold axis containing the metal
atom. In 2, the Na plane defines dihedral angles of 3.66-
4)° and 1.80(5)° with the S(1) and S(2) planes, respec-
triangle is twisted with respect to the S(1)
O, Na-S, and Na-N distances in 5 [2.53(10), 2.91(10), and
.48(7) Å] can be compared with the corresponding values
in the crown-ether-coordinated sodium pyridine-2-thiolate
complexes [Na(15c5)(NC S-2)] [2.5(1), 3.038(1), and
.429(3) Å] and [Na(18c6)(NC S-2)] [2.6(1), 2.764(1), and
.649(2) Å]. The coordination mode of the K (18c6) unit
(18c6) in 3, is similar
(dicyclohexyl-18c6) in [{K(OPh) (dicyclohexyl-
8c6)], while the structure of the latter is very different
from that of its sodium counterpart in which one sodium
atom is coordinated to the six hexaether oxygen atoms and
the other sodium atom is linked to only one of the crown
oxygen atoms. The average K-O and K-S distances of
2
3
5
H
4
3
3
2
2
5 4
H
4
3
2
3
in 4, which is identical to that of Na
to that of K
1
2
(
3
3
2
2 2
}
tively. The Na
3
3
4
4
and S(2)
Figure 6), and is located between these S
distance of 0.6577(4) Å from the Nd atom, on the side of
the S(1) atoms. The M and S(1) triangles in 3-5 are slightly
rotated from their eclipsed conformation, by a twist angle
of 10-20°, and the M triangle is farther away than the
staggered S(2) triangle from the metal center, at a distance
of 2.201(3), 2.3334(6), and 2.3979(16) Å, respectively
Figure 5). In all the complexes, each Na or K atom is bound
3
triangles by an angle of ca. 30 and 9°, respectively
(
3
planes at a
3
3
2
.83(8) and 3.22(5) Å in 4 are normally larger than the mean
Na-O and Na-S bond lengths in 3 and 5 and are similar to
those of 2.90(2) and 3.2558(1) Å in [K(18c6)(NC
S-2)];43
the mean K-O bond length can be compared with that of
.84(8) Å in the aforementioned potassium phenoxide
3
3
5 4
H
(
2
to the S(1) and S(2) atoms of one dddt ligand and to one
sulfur atom of another one, S(4) in 2 and S(2) in 3-5; the
S(2B) atoms are thus in triply bridging position in 3-5.
These differences between 2 and 3-5 are obviously related
to the distinct coordination of the alkali metal atoms. The
Na atoms in 2 are lying on inversion centers and bridge the
44
complex. Distances of ca. 3.3-3.4 Å are observed between
each potassium atom and the S(3) atom of the neighboring
dddt ligand, likely reflecting weaker interactions; thus, there
is some uncertainty in the K coordination number (six or
+
seven). The crystal structures of the [Na(18c6)(py)
x
] cations
(x ) 1 or 2), present in 1 and 2, have not been reported
Nd(dddt)
3
units whereas the Na or K atoms in 3-5 are
previously; the octahedral or hexagonal pyramidal coordina-
bound, in addition to the three sulfur atoms of the Ln(dddt)
3
tion geometry of the alkali metal is identical to that found
unit, to three or four oxygen atoms of a bridging 18c6
molecule or, in the case of Na(1) in 5, to two nitrogen atoms
of pyridine ligands; the middle of the Na‚‚‚Na segment in
each Na (18c6) moiety is an inversion center. The six-
2
coordinate Na atoms in 2, 3, and 5 are in distorted octahedral
environment and the seven-coordinate ones in 3 [Na(2)] and
+
45
+ 46
in [Na(18c6)(THF)
2
] , [K(18c6)(py)
2
] , or [Na(18c6)-
+
i
47
(OR
2
)] (R ) Et or Pr). The Na-O and Na-N bond
lengths, with average values of 2.72(12) and 2.47(5) Å, are
unexceptional.
As indicated above, the anionic fragments [Na1.5Nd-
1.5-
3
(dddt) ]
in compound 2 are associated in a bidimensional
5
[Na(3)] in distorted capped octahedral environments; the
coordination polymer with a honeycomb net structure
represented in Figure 2b. Each roughly planar hexagonal cell
consists of six Nd and six Na atoms held alternately in a
ring by 18 dddt ligands. The Nd atoms constitute the trigonal
nodes whereas the Na atoms act as spacers and define the
sides of the hexagons, which have a length of 8.7169(9) Å.
Each dddt ligand is bound to one Nd and two Na atoms and
pertains to all three adjacent hexagonal cells around the Nd
atom. These planar assemblages are parallel to the ab plane,
and the successive layers, separated by ca. 15 Å, would
Na(1) atom in 5 adopts a trigonal bipyramidal configuration
with N(2) and S(1A) in apical positions. The geometry of
the Na
Na (dicyclohexyl-18c6) which ensures the bridging of two
Co(salen) units in [{Co(salen)Na}
Na-O distances are ranging between 2.417(11) and 2.856-
6) Å with an average value of 2.5(2) Å which is identical
2
(18c6) moieties in 3 and 5 is very similar to that of
2
38
2
(dicyclohexyl-18c6)]; the
(
to that found in the cobalt compound. The Na-S bond
lengths in 2, 3, and 5 vary from 2.762(3) to 3.168(4) Å,
except Na(1)-S(4C) in 2 which is equal to 3.446(2) Å; the
average values of 2.99(18) Å in 2, 3.00(10) in 3, and 2.91-
define channels along the c axis, but for the presence of the
+
[Na(18c6)(py)
x
] cations in the interlayer spaces. The mean
(
10) Å in 5 are quite similar to the Na-S distance in [Na-
t
(41) Berardini, M.; Emge, T. J.; Brennan, J. G. Inorg. Chem. 1995, 34,
327.
42) Xie, X.; McCarley, R. E. Inorg. Chem. 1997, 36, 4665.
(43) Chadwick, S.; Ruhlandt-Senge, K. Chem. Eur. J. 1998, 4, 1768.
3 2 6
(THF) ] [U(SR) ], 2.965(8) and 3.060(3) Å for R ) Bu or
5
39
Ph respectively, or the average Na-S distance of 2.9(1) Å
for the NaS octahedra of Na AsS . The Na(1)-N(2) and
6 3 3
(
40
(44) Fraser, M. E.; Fortier, S.; Rodrigue, A.; Bovenkamp, J. W. Can. J.
Chem. 1986, 64, 816.
(
(
(
(
37) Fourmigu e´ , M.; Lenoir, C.; Coulon, C.; Guyon, F.; Amaudrut, J. Inorg.
(45) Le Mar e´ chal, J. F.; Villiers, C.; Charpin, P.; Nierlich, M.; Lance, M.;
Vigner, J.; Ephritikhine, M. J. Organomet. Chem. 1989, 379, 259.
(46) Tripepi, G.; Young, V. G.; Ellis, J. E. J. Organomet. Chem. 2000,
593, 354.
(47) (a) Uhl, W.; Hannemann, F.; Saak, W.; Wartchow, R. Eur. J. Inorg.
Chem. 1998, 921. (b) Uhl, W.; Hannemann, F. J. Organomet. Chem.
1999, 579, 18.
Chem. 1995, 34, 4979.
38) Gambarotta, S.; Arena, F.; Floriani, C.; Zanazzi, P. F. J. Am. Chem.
Soc. 1982, 104, 5082.
39) Leverd, P. C.; Lance, M.; Nierlich, M.; Vigner, J.; Ephritikhine, M.
J. Chem. Soc., Dalton Trans. 1993, 2251.
40) Palazzi, M. Acta Crystallogr., Sect. B 1976, 32, 3175.
Inorganic Chemistry, Vol. 44, No. 3, 2005 591

Roger et al.
planes defined by the six oxygen atoms of the two crystal-
lographically independent crown ethers make dihedral angles
of 71.64(8)° and 72.07(8)° with the honeycomb plane. When
+
viewed along the c axis, the [Na(18c6)(py)
2
] cation projects
alongside a hexagon side, with the Na atom superposed to
that defining the side, whereas the disordered [Na(18c6)-
+
(
py)1.5] moiety projects at the center of the hexagonal cell.
Honeycomb networks are also found in compounds 3 and
4
(Figure 3b), but the situation is quite different since these
polymers are now neutral. The hexagonal cells comprise six
Nd atoms as trigonal nodes and 12 M (Na in 3, K in 4) atoms,
each side corresponding to a M (18c6) fragment. The
2
resulting size of the cells is larger than in 2, with a side
length of 11.9183(16) Å. In contrast to the planar hexagons
found in 2, the hexagonal rings in 3 and 4 are strongly
puckered, with the Nd atoms alternately above and below
the mean plane defined by the Na or K atoms. As in
compound 2, each dddt ligand is bound to one Nd and two
M atoms. The 2D polymer formed is parallel to the bc plane,
and hexagonal channels are formed along the a axis, with
an effective inner diameter of ca. 8-9 Å (van der Waals
radii excluded). The interlayer separation is close to the a
parameter, 10.1439(8) and 10.3168(5) Å in 3 and 4,
respectively. In the absence of counterions, the channels are
occupied by the solvent molecules only (much disordered
in compound 4).
Figure 7. øMT versus T plot for 2.
5
4
depopulated, even at room temperature. The Zeeman factor
8
3
g
J
is then equal to /11, affording a ø
M
T value of 1.64 cm K
-
1
mol . The experimental ø
in Figure 7. At room temperature, ø
K mol as predicted above from the free-ion I9/2 ground
M
T versus T curve for 2 is shown
3
M
T amounts to 1.65 cm
-
1
4
state. Upon lowering the temperature, ø T decreases down
M
Although honeycomb net structures are less frequent in
metal-organic than in organic compounds,48 several ex-
amples have been reported, with either ligand49 or metal
moieties as trigonal nodes. In the case of rare earth metal
ions, honeycomb networks have been considered in the
search for new magnetic properties.51
3
-1
to 0.6 cm K mol , indicating strong deviations from the
Curie law. This behavior, already observed in molecular Nd
complexes with (O, N) ligands, has been rationalized by
50
52
Andruh et al. from a contribution of the crystal field which
4
splits the I9/2 free-ion ground state into five Kramers
doublets, equally populated at 300 K (hence the free-ion
approximation value) but progressively depopulated as T
decreases.
In compound 5, the arrangement around each lanthanide
atom is nearly the same as in 3 and 4, but one of the three
sodium atoms is bound to two pyridine molecules instead
of a crown ether. This results in an interruption of the
bidimensional pattern and the formation of a zigzag poly-
meric chain running along the (101) direction, with succes-
sive cerium atoms separated by 11.5891(13) and 11.9471(14)
Å and Ce‚‚‚Ce‚‚‚Ce angles of 105.610(10)° (Figure 4).
Successive chains in the bc plane are offset with respect to
the position they would occupy in a honeycomb arrangement,
and as a result, no wide channel is formed.
Conclusion
We have synthesized the first tris(dithiolene) complexes
of an f element, which are also the first lanthanide dithiolene
compounds to have been crystallographically characterized.
The structure of these compounds, which all contain the [Ln-
3
(dddt) ] unit, is dependent on the nature of the lanthanide
+
+
metal (Nd, Ce), the counterion (Na or K ), the solvent (THF
or pyridine), and the amount of 18c6 which is necessary to
induce crystallization. After the d transition metal complexes
Magnetic Properties. The peculiar honeycomb structure
of the single true homoleptic complex 2 led us to further
5
5
5
2,53
[NEt ] [Ru(mnt) ], [PPh ] [Cr(mnt) ] (mnt ) 1,2-dicyano-
characterize its magnetic properties in the solid state.
The
4 3
3
4 3
3
5
6
57
4
4 3 3
ethylene dithiolate), and [PPh ] [Co(dithiocrotonate) ], the
free-ion ground state of Nd(III) is I9/2. The first excited state,
11/2, is located at 2000 cm above, so that it is fully
4
-1
compounds reported here are new trianionic tris(dithiolene)
derivatives characterized by their crystal structure. The use
I
+
+
(
48) Moulton, B.; Zaworotko, M. J. Chem. ReV. 2001, 101, 1629 and
of alkali metal ions in place of [NEt
us to obtain, in addition to monomeric species, infinite chains
in which each Ln(dddt) unit is linked to two neighbors by
Na (18c6) fragments, or two-dimensional neutral or anionic
4 4
] and [PPh ] allowed
references therein.
(
(
49) Choi, H. J.; Suh, M. P. J. Am. Chem. Soc. 1998, 120, 10622.
50) (a) Kim, Y.; Verkade, J. G. Inorg. Chem. 2003, 42, 4262. (b)
Mukhopadhyay, S.; Chatterjee, P. B.; Mandal, D.; Mostafa, G.;
Caneschi, A.; van Slageren, J.; Weakley, T. J. R.; Chaudhury, M.
Inorg. Chem. 2004, 43, 3413.
3
2
(
(
(
51) Daiguebonne, C.; Guillou, O.; Kahn, M. L.; Kahn, O.; Oushoorn, R.
(54) Carlin, R. L. In Magnetochemistry; Springer-Verlag: Berlin, 1986;
Chapter 9.
(55) Maiti, R.; Shang, M.; Lappin, A. G. Chem. Commun. 1999, 2349.
(56) Lewis, G. R.; Dance, I. J. Chem. Soc., Dalton Trans. 2000, 3176.
(57) Heuer, W. B.; Pearson, W. H. Polyhedron 1996, 15, 2199.
L.; Boubekeur, K. Inorg. Chem. 2001, 40, 176.
52) Andruh, M.; Bakalbassis, E.; Kahn, O.; Trombe, J. C.; Porcher, P.
Inorg. Chem. 1993, 32, 1616.
53) Kahn, O. In Molecular Magnetism; VCH: Weinheim, 1993.
592 Inorganic Chemistry, Vol. 44, No. 3, 2005

Nd and Ce Tris(dithiolene) Complexes
layers in which each Ln(dddt)
Na (18c6) fragments or Na atoms to form a honeycomb
network.
3
unit is surrounded by three
Supporting Information Available: Tables of crystal data,
atomic positions and displacement parameters, anisotropic displace-
ment parameters, bond lengths, and bond angles in CIF format.
This material is available free of charge via the Internet at
http://pubs.acs.org.
2
Acknowledgment. We warmly thank Pr. M. Andruh,
from the University of Bucarest (Romania), for enlightening
discussions on the magnetic properties of those rare-earth
complexes.
IC049055I
Inorganic Chemistry, Vol. 44, No. 3, 2005 593