Heterometallic Ln/Hg compounds with fluorinated thiolate ligands

Article abstract of DOI:10.1021/ic049215q

The early lanthanide benzenefluorothiolates (Ln(SC₆F ₅)₃; Ln = La, Ce, Pr, Nd, Sm, Gd) react with Hg(SC ₆F₅)₂ in DME to form ionic heterometallic compounds with Ln cations and Hg anions. X-ray diffraction analyses of all compounds reveal an isostructural series with the general formula [(DME) ₃Ln(SC₆F₅)₂]₂[Hg ₂(SC₆F₅)₆]. In the structures, a fluorothiolate ligand has been extracted from the Ln coordination sphere that is saturated with three neutral DME donor ligands and a dative interaction between one ortho fluorine and the Ln. Distances between Ln and F do not vary simply with Ln ionic radius. There are two Ln cations with charge balanced by a Hg ₂(SC₆F₅)₆ dianion composed of two distinctly nonideal Hg(II) tetrahedra, all connected through a series of π-π interactions that link cations with anions in a one-dimensional array and anions to anions in a more complex 2D network.

Full text of DOI:10.1021/ic049215q

Inorg. Chem. 2004, 43, 6307−6312
Heterometallic Ln/Hg Compounds with Fluorinated Thiolate Ligands
Santanu Banerjee, Thomas J. Emge, and John G. Brennan*
Department of Chemistry and Chemical Biology, Rutgers, the State UniVersity of New Jersey,
610 Taylor Road, Piscataway, New Jersey 08854-8087
Received June 16, 2004
The early lanthanide benzenefluorothiolates (Ln(SC6F5)3; Ln
) La, Ce, Pr, Nd, Sm, Gd) react with Hg(SC6F5)2 in
DME to form ionic heterometallic compounds with Ln cations and Hg anions. X-ray diffraction analyses of all
compounds reveal an isostructural series with the general formula [(DME)3Ln(SC6F5)2]2[Hg2(SC6F5)6]. In the structures,
a fluorothiolate ligand has been extracted from the Ln coordination sphere that is saturated with three neutral DME
donor ligands and a dative interaction between one ortho fluorine and the Ln. Distances between Ln and F do not
vary simply with Ln ionic radius. There are two Ln cations with charge balanced by a Hg2(SC6F5)6 dianion composed
of two distinctly nonideal Hg(II) tetrahedra, all connected through a series of π−π interactions that link cations with
anions in a one-dimensional array and anions to anions in a more complex 2D network.
Introduction
ture describing the use of pseudohalide ligands (CN,2 SCN,3
SPh,4 SePh5) to connect Ln with M, and a recent description
of a LnHg compound with an iodide linkage.6 Within this
molecular class, both charge neutral and ionic species have
been prepared. The more conventional ionic ligands tend to
maintain Ln-L connectivity, whereas ligands that prefer-
entially form more covalent bonds are often expelled from
Ln coordination spheres, giving rise to ionic species with
solvated Ln.
Lanthanide compounds with certain pseudohalogen ligands
will react with elemental chalcogen, reducing the chalcogen
and oxidizing the pseudohalide, to form chalcogenido
clusters.7 This redox reactivity roughly parallels that of the
ligand displacement chemistry. More covalent ligands (i.e.,
SPh, SePh, TePh) are readily abstracted from Ln, and they
react with elemental E, reducing E to give E2- with
concomitant oxidation of L- to give L-L. In contrast, the
more ionic ligands remain coordinated to Ln and do not react
with elemental E (i.e., halogens). Finally, there are ligands
with intermediate reactivity patterns, i.e., CN, SCN, and the
halides, which can be extracted from Ln coordination spheres
but do not appear to reduce elemental E. An extension of
this chemistry to heterometallic systems led to the preparation
of selenido cluster salts, with separate cationic Ln4Se and
anionic M4Se cluster cores.7a
Heterometallic compounds containing lanthanides (Ln) and
transition metals (M) continue to be investigated as poten-
tially useful electronic materials with readily tailored elec-
tronic or magnetic properties.1-6 There is an extensive litera-
* To whom correspondence should be addressed. E-mail: bren@
rutchem.rutgers.edu.
(1) (a) Imbert, D.; Cantuel, M.; Buenzli, J.; Bernardinelli, G.; Piguet, C.
J. Am. Chem. Soc. 2003, 125, 15698-15699. (b) Rodriguez-Cortinas,
R.; Avecilla, F.; Platas-Iglesias, C.; Imbert, D.; Buenzli, J.; de Blas,
A.; Rodriguez-Blas, T. Inorg. Chem. 2002, 41, 5336-5349. (c)
Buenzli, J. G.; Piguet, C. Chem. ReV. 2002, 102, 1897-1928. (d)
Glover, P. B.; Ashton, P. R.; Childs, L. J.; Rodger, A.; Kercher, M.;
Williams, R. M.; De Cola, L.; Pikramenou, Z. J. Am. Chem. Soc. 2003,
125, 9918-9919. (e) Lin, X.; Doble, D. M. J.; Blake, A. J.; Harrison,
A.; Wilson, C.; Schroeder, M. J. Am. Chem. Soc. 2003, 125, 9476-
9483. (f) He, Z.; He, C.; Gao, E.; Wang, Z.; Yang, X.; Liao, C.; Yan,
C. Inorg. Chem. 2003, 42, 2206-2208. (g) Cui, Y.; Qian, Y.-T.;
Huang, J.-S. Polyhedron 2001, 20, 1795-1802.
(2) (a) James, C.; Willand, P. S. J. Am. Chem. Soc. 1916, 38, 1497. (b)
Bailey, W. E.; Williams, R. J.; Milligan, W. O. Acta Crystallogr. 1973,
B29, 1365. (c) Knoeppel, D. W.; Liu, J.; Meyers, E. A.; Shore, S. G.
Inorg. Chem. 1998, 37, 4828-4837. (d) Liu, J.; Knoeppel, D. W.;
Liu, S.; Meyers, E. A.; Shore, S. G. Inorg. Chem. 2001, 40, 2842-
2850. (e) Du, B.; Meyers, E. A.; Shore, S. G. Inorg. Chem. 2001, 40,
4353-4360. (f) James, C.; Willand, P. S. J. Am. Chem. Soc. 1916,
38, 1497. (g) Harada, K.; Yuzunihara, J.; Ishii, Y.; Sato, N.;
Kambayashi, H.; Fukada, Y. Chem. Lett. 1995, 887.
(3) Amirkhanov, V. M.; Kapshuk, A. A.; Kramarenko, F. G.; Skopenko,
V. V. Russ. J. Inorg. Chem. 1994, 39, 1155.
(4) Brewer, M.; Emge, T.; Brennan, J. Inorg. Chem. 1995, 34, 5919-24.
(5) (a) Freedman, D.; Emge, T. J.; Brennan, J. G. J. Am. Chem. Soc. 1997,
119, 11112-3. (b) Lee, J.; Emge, T.; Brennan, J. Inorg. Chem. 1997,
36, 5064-8. (c) Berardini, M.; Emge, T.; Brennan, J. Inorg. Chem.
1995, 34, 5327. (d) Berardini, M.; Emge, T.; Brennan, J. J. Am. Chem.
Soc. 1994, 116, 6941.
Fluorinated benzenethiolate (SC6F5) is a particularly in-
teresting ligand for lanthanide compounds, because the fluor-
(6) Huebner, L.; Emge, T. J.; Brennan, J. G. Inorg. Chem. 2004, 43, 5659-
(7) (a) Kornienko, A.; Huebner, L.; Freedman, D.; Emge, T.; Brennan, J.
5664.
Inorg. Chem. 2003, 42, 8476-80.
10.1021/ic049215q CCC: $27.50
Published on Web 09/03/2004
© 2004 American Chemical Society
Inorganic Chemistry, Vol. 43, No. 20, 2004 6307

Banerjee et al.
at the bottom of the flask. The colorless solution was filtered away
and reduced in volume under vacuum to ca. 10 mL and layered
with hexane (10 mL) to give colorless plate-shaped crystals
on cooling at 15 °C (0.30 g, 88%) that melt between 75 and
80 °C, turn light yellow at 100 °C, darken between 170 and 175
°C, and remain dark brown from 200 to 350 °C. IR: 2950 (w),
2920 (w), 2856 (w), 2407 (s), 2343 (s), 1631 (s), 1456 (m), 1374
(m), 1345 (m), 1299 (m), 1252 (m), 1077 (s), 1001 (s), 960 (s),
709 (s) cm-1. UV-vis.: no absorption maximum from 300 to 750
nm when dissolved in either THF or pyridine. Anal. Calcd for
C92H80F50Hg2O16S10La2: C, 32.6; H, 2.36. Found: C, 32.2; H, 2.50.
19F NMR (CD3CN, 24 °C): -162.57 (1F, w1/2 ) 90 Hz); -161.68
(2F, w1/2 ) 136 Hz); -130.95 (2F, w1/2 ) 90 Hz). There was no
change in line shape as a function of temperature. Method B
follows: La (0.14 g, 1.0 mmol) and Hg(SC6F5)2 (0.90 g, 1.5 mmol)
were combined in DME (ca. 20 mL), and the mixture was stirred
overnight until all the metal was consumed with the appearance of
elemental mercury at the bottom of the flask. The colorless solution
was filtered away from the mercury (0.25 g, 82%), and Hg(SC6F5)2
(0.60 g, 1.0 mmol) was added to the solution and stirred overnight
to give a colorless solution with a gray powdery precipitate at the
bottom of the flask. The colorless solution was filtered, reduced in
volume under vacuum (10 mL), and layered with 10 mL of hexane
to give colorless plate-shaped crystals upon cooling at 15 °C (0.30
g, 88%).
inated organic ring imparts useful solubility properties. For
example, (solvent)6Ln4E(EE)4(SC6F5)2 dissolve readily in
toluene,8 whereas (solvent)6Ln4E(EE)4(EPh)2 (E ) S, Se, Te)
are soluble only in Lewis base solvents. The fluorocarbon
moiety also imparts curious structural features, including
extensive π-π stacking interactions,9 and in lanthanide
chemistry there exists a distinct tendency to exhibit dative
Ln-F interactions.10 In redox reactions of Ln(SC6F5)3 with
elemental E, the fluorothiolate ligand did not react, thus
presenting an opportunity to prepare the aforementioned
toluene soluble clusters.
While displacement chemistry (or the lack thereof) with
SC6F5 has been examined, heterometallic Ln compounds
incorporating SC6F5 have not yet been described. Because
hydrocarbon soluble heterometallic compounds could be
useful for doping Ln/M into a variety of organic based
optoelectronic devices, we set out to establish whether
Ln(SC6F5)3 would react with Hg(SC6F5)2 to form discrete
products. This work outlines the first successful preparation
of heterometallic fluorothiolate compounds containing both
Ln and Hg, the first structural characterization of heterome-
tallic compounds containing SC6F5 ligands, and the first
attempt to evaluate how Ln ionic radius influences the length
of dative Ln-F bonds.
Synthesis of [(DME)3Ce(SC6F5)2]2[Hg2(µ-SC6F5)2(SC6F5)4]‚
2DME (2). As for 1 above, Ce (0.14 g, 1.0 mmol) and Hg(SC6F5)2
(1.50 g, 2.5 mmol) in DME (ca. 20 mL) gave colorless small rod
shaped crystals (0.28 g, 82%). The crystals melt (colorless liquid)
between 80 and 82 °C; the liquid then turns pale yellow at 120 °C,
and then dark brown around 220 °C. IR: 2925 (w), 2725 (s), 2593
(s), 2396 (s), 2351 (s), 1622 (m), 1575 (s), 1463 (w), 1385 (w),
1296 (m), 1261 (w), 1085 (w), 970 (w), 857 (w), 712 (s), 622 (s)
cm-1. UV-vis: no absorption maximum from 300 to 750 nm in
either THF or pyridine. Anal. Calcd for C92H80F50Hg2O16S10Ce2:
C, 32.5; H, 2.36. Found: C, 32.0; H, 2.22. 19F NMR (CD3CN, 24
°C): -162.69 (1F, w1/2 ) 91 Hz); -161.56 (2F, w1/2 ) 136 Hz);
-131.2 (2F, w1/2 ) 90 Hz). There was no change in line shape as
a function of temperature. Method B follows: As for 1 above, Ce
(0.14 g, 1.0 mmol) and sequential additions of Hg(SC6F5)2 (0.90
g, 1.5 mmol and 0.60 g, 1 mmol) in DME (ca. 20 mL) produced
colorless small rod-shaped crystals (0.28 g, 82%).
Experimental Section
General Methods. All syntheses were carried out under high
purity nitrogen (Airgas), using conventional drybox or Schlenk
techniques. Solvents (Aldrich) were either refluxed continuously
over molten alkali metals or K/benzophenone and collected
immediately prior to use, or purified with a dual column Solv-Tek
solvent purification system. Lanthanides were purchased from
Strem. Hg(SC6F5)2 was prepared according to the modified10a
literature procedure.11 Melting points were taken in sealed capillaries
and are uncorrected. IR spectra were taken on a Thermo Nicolet
Avatar 360 FTIR spectrometer, and recorded from 4000 to 600
cm-1 as a Nujol mull on NaCl plates. Mass spectra were recorded
on a Finnigan LCQ-DUO mass spectrometer using acetonitrile as
a solvent. Electronic spectra were recorded on a Varian DMS 100S
spectrometer with the samples in a 0.10 mm quartz cell attached
to a Teflon stopcock. Elemental analyses were performed by
Quantitative Technologies, Inc. (Whitehouse NJ). The compounds
are slightly air sensitive and will eventually lose lattice DME when
exposed to air.
Synthesis of [(DME)3Pr(SC6F5)2]2[Hg2(µ-SC6F5)2(SC6F5)4]‚
2DME (3). As for 1 above, Pr (0.14 g, 1.0 mmol) and Hg(SC6F5)2
(1.50 g, 2.5 mmol) in DME (ca. 20 mL) gave pale green plate-
shaped crystals (0.33 g, 97%) that melt between 72 and 75 °C.
The liquid turns deeper green at 140 °C and changes from light
brown to dark brown between 245 and 350 °C. IR: 2926 (w), 2729
(w), 2397 (s), 2255 (s), 1711 (s), 1659 (s), 1622 (s), 1579 (w),
1456 (w), 1386 (w), 1257 (w), 1089 (w), 824 (w), 721 (m), 623
(s) cm-1. UV-vis: no absorption maximum from 300 to 750 nm
in either THF or pyridine. Anal. Calcd for C92H80F50Hg2O16S10Pr2:
C, 32.5; H, 2.35. Found: C, 31.7; H, 2.19. 19F NMR (CD3CN, 24
°C): -162.79 (1F, w1/2 ) 136 Hz); -161.22 (2F, w1/2 ) 136 Hz);
-131.45 (2F, w1/2 ) 272 Hz). There was no change in line shape
as a function of temperature. Method B follows: As for 1, Pr (0.14
g, 1.0 mmol) and sequential additions of Hg(SC6F5)2 (0.90 g, 1.5
mmol and 0.60 g, 1 mmol) in DME (ca. 20 mL) gave pale green
crystals (0.33 g, 97%).
Synthesis of [(DME)3La(SC6F5)2]2[Hg2(µ-SC6F5)2(SC6F5)4]‚
2DME (1). Method A follows: La (0.14 g, 1.0 mmol) and
Hg(SC6F5)2 (1.50 g, 2.5 mmol) were combined in DME (ca. 20
mL), and the mixture was stirred until all the metal was consumed
(1 day) to give a colorless solution with black powdery precipitate
(8) Fitzgerald, M.; Emge, T. J.; Brennan, J. G. Inorg. Chem. 2002, 41,
3528-43.
(9) (a) Anderson, K. M.; Baylies, C. J.; Monowar-Jahan, A. H. M.;
Norman, N. C.; Orpen, A. G.; Starbuck, J. Dalton Trans. 2003, 3270-
3277. (b) Crespo, O.; Canales, F.; Gimeno, M. C.; Jones, P. G.;
Laguna, A. Organometallics 1999, 18, 3142-3148. (c) Uson, M. A.;
Llanos, J. M. J. Organomet. Chem. 2002, 663, 98-107. (d) Carmalt,
C. J.; Dinnage, C. W.; Parkin, I. P.; White, A. J. P.; Williams, D. J.
Dalton 2000, 3500-3504. (e) Chadwick, S.; Englich, U.; Noll, B.;
Ruhlandt-Senge, K. Inorg. Chem. 1998, 37, 4718-4725.
(10) (a) Melman, J.; Rhode, C.; Emge, T. J.; Brennan, J. G. Inorg. Chem.
2002, 41, 28-33. (b) Melman, J.; Emge, T. J.; Brennan, J. G. Inorg.
Chem. 2001, 40, 1078-81.
Synthesis of [(DME)3Nd(SC6F5)2]2[Hg2(µ-SC6F5)2(SC6F5)4]‚
2DME (4). As for 1, Nd (0.14 g, 1.0 mmol) and Hg(SC6F5)2 (1.50
g, 2.5 mmol) in DME (ca. 20 mL) gave, upon cooling to 5 °C,
colorless crystals (0.27 g, 79%) that melt between 70 and 74 °C.
(11) Peach, M. E. J. Inorg. Nucl. Chem. 1973, 35, 1046.
6308 Inorganic Chemistry, Vol. 43, No. 20, 2004

Ln/Hg Compounds with Fluorinated Thiolate Ligands
Table 1. Summary of Crystallographic Details for 1-6
1
2
3
4
5
6
Ln in empirical formula
La
Ce
Pr
Nd
Sm
Gd
C92H80F50Hg2O16S10Ln2
fw
3391.16
P1h
3393.58
P1h
3395.16
P1h
3401.82
P1h
3414.04
P1h
3427.84
P1h
space group
a (Å)
b (Å)
12.6352(7)
13.1976(7)
19.6962(10)
87.021(1)
83.928(1)
63.923(1)
2933.5(3)
1
12.6701(7)
13.2133(7)
19.6719(11)
87.041(1)
84.001(1)
63.974(1)
2943.1(3)
1
12.6591(6)
13.1702(7)
19.5725(10)
87.046(1)
84.107(1)
64.036(1)
2918.2(3)
1
12.6488(7)
13.2025(7)
19.5108(10)
87.149(1)
84.017(1)
64.092(1)
2914.8(3)
1
12.6489(10)
13.1545(11)
19.4412(16)
87.170(2)
83.838(2)
64.053(1)
2891.9(4)
1
12.6757(6)
13.1765(6)
19.4107(9)
87.270(1)
83.758(1)
64.065(1)
2898.2(2)
1
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
D(calcd) (g/cm-3
T (°C)
)
1.920
-173
0.71073
3.638
0.046
0.096
1.915
-173
0.71073
3.674
0.055
0.113
1.932
-173
0.71073
3.760
0.039
0.091
1.938
-173
0.71073
3.819
0.069
0.114
1.960
-173
0.71073
3.967
0.057
0.131
1.964
-173
0.71073
4.090
0.044
0.102
λ (Å)
abs coeff (mm-1
)
R(F)a [I > 2 σ(I)]
Rw(F2)a [I > 2 σ(I)]
a Definitions: R(F) ) ∑||Fo| - |Fc||/∑|Fo|; Rw(F2) ) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2. Additional crystallographic details are given in the Supporting
2
2
2
Information.
The liquid turns light yellow at around 160 °C and dark brown
between 230 and 350 °C. IR: 2918 (w), 2722 (w), 2395 (m), 2360
(m), 2249 (s), 2208 (s), 2022 (s), 1975 (s), 1934 (s), 1712 (s), 1655
(s), 1619 (m), 1564 (s), 1456 (w), 1327 (w), 1251 (w), 1187 (w),
861 (w), 726 (w), 616 (s) cm-1. UV-vis: no absorption maximum
from 300 to 750 nm in either THF or pyridine. Anal. Calcd for
C92H80F50Hg2O16S10Nd2: C, 32.5; H, 2.35. Found: C, 31.6; H, 2.19.
19F NMR (CD3CN, 24 °C): -162.52 (1F, w1/2 ) 210 Hz); -160.5
(2F, w1/2 ) 210 Hz); -131.32 (2F, w1/2 ) 210 Hz). There was no
change in line shape as a function of temperature. Method B
follows: As for 1 above, Nd (0.14 g, 1.0 mmol) and sequential
addition of Hg(SC6F5)2 (0.90 g, 1.5 mmol and 0.60 g, 1.0 mmol)
in DME (ca. 20 mL) gave colorless crystals upon cooling at 15 °C
(0.27 g, 79%). Thermal decomposition: 4 was placed in a quartz
tube sealed under vacuum. The end charged with the compound
was placed in a tube furnace while the other end was immersed in
liquid nitrogen. The temperature was ramped to 700 °C at a rate of
20°/min, and then held for 3 h. Analysis of the residual solid-state
material with a Bruker D8 Advance XRP diffractometer identified
NdF3 as the only crystalline solid-state product present.12
Synthesis of [(DME)3Sm(SC6F5)2]2[Hg2(µ-SC6F5)2(SC6F5)4]‚
2DME (5). Method Afollows: As for 1, Sm (0.15 g, 1.0 mmol)
and Hg(SC6F5)2 (1.50 g, 2.5 mmol) in DME (ca. 20 mL) gave light
yellow plate-shaped crystals on cooling at 15 °C (0.29 g, 84%).
The compound melts between 72 and 75 °C, turns yellow at 140
°C, and changes from light brown to dark brown between 245 and
350 °C. IR: 2926 (w), 2729 (w), 2397 (s), 2255 (s), 1711 (s), 1659
(s), 1622 (s), 1579 (w), 1456 (w), 1386 (w), 1257 (w), 1089 (w),
824 (w), 721 (m), 623 (s) cm-1. UV-vis: no absorption maximum
from 300 to 750 nm in either THF or pyridine. Anal. Calcd for
C92H80F50Hg2O16S10Sm2: C, 32.3; H, 2.34. Found: C, 32.1; H, 2.00.
19F NMR (CD3CN, 24 °C): -162.84 (1F, w1/2 ) 141 Hz); -161.42
(2F, w1/2 ) 140 Hz); -131.61 (2F, w1/2 ) 98 Hz). There was no
change in line shape as a function of temperature. Method B
follows: As for 1, Sm (0.15 g, 1.0 mmol) and sequential additions
of Hg(SC6F5)2 (0.90 g, 1.5 mmol and 0.60 g, 1 mmol) in DME
(ca. 20 mL) gave light yellow plate-shaped crystals (0.29 g, 84%).
Synthesis of [(DME)3Gd(SC6F5)2]2[Hg2(µ-SC6F5)2(SC6F5)4]‚
2DME (6). As for 1, Gd (0.157 g, 1.0 mmol) and Hg(SC6F5)2 (1.50
g, 2.5 mmol) in DME (ca. 20 mL) gave colorless small rodlike
crystals (0.28 g, 82%) which melt (colorless liquid) between 65
and 70 °C. The liquid turns pale yellow at 160 °C and continues to
a dark brown color between 230 and 350 °C. IR: 2922 (w), 2725
(m), 2391 (s), 2251 (s), 1706 (s), 1657 (s), 1625 (s), 1577 (s), 1462
(w), 1363 (w), 1258 (w), 1088 (w), 1018 (w), 865 (m), 804 (m),
722 (m) cm-1. UV-vis: no absorption maximum from 300
to 750 nm in either THF or pyridine. Anal. Calcd for
C92H80F50Hg2O16S10Gd2: C, 32.2; H, 2.33. Found: C, 31.5; H, 2.46.
19F NMR (CD3CN, 24 °C): -162.77 (1F, w1/2 ) 101 Hz); -161.22
(2F, w1/2 ) 105 Hz); -131.45 (2F, w1/2 )196 Hz). There was no
change in line shape as a function of temperature. Method B
follows: As for 1 above, Gd (0.16 g, 1.0 mmol) and sequential
addition of Hg(SC6F5)2 (0.90 g, 1.5 mmol and 0.60 g, 1.0 mmoL)
in DME (ca. 20 mL) gave colorless crystals upon cooling at 15 °C
(0.28 g, 82%).
X-ray Structure Determination of 1-6. Data for 1-6 were
collected on a Bruker Smart APEX CCD diffractometer with
graphite monochromatized Mo KR radiation (λ ) 0.71073 Å) at
100 K. The data were corrected for Lorenz effects and polarization,
and absorption, the latter by a multiscan (SADABS)13 method. The
structures were solved by Patterson or direct methods (SHELXS86).14
All non-hydrogen atoms were refined (SHELXL97)15 on the basis
of Fobs2. All hydrogen atom coordinates were calculated with
idealized geometries (SHELXL97). Scattering factors (fo, f ′, f ′′)
are as described in SHELXL97. Crystallographic data and final R
indices for 1-6 are given in Table 1. A generic ORTEP diagram16
for 1-6 is shown in Figure 1. Significant bond geometries for 1-6
are given in Table 2. Complete crystallographic details for 1-6
are given in the Supporting Information.
Results
Lanthanide benzenefluorothiolates (Ln(SC6F5)3; Ln ) La,
Ce, Pr, Nd, Sm, Gd) react with mercury benzenefluoro-
thiolate to form ionic heterometallic compounds with the
general formula [(DME)3Ln(SC6F5)2]2[Hg2(SC6F5)6] (Ln )
La (1), Ce (2), Pr (3), Nd (4), Sm (5), Gd (6)). These
(12) Staritzky, E.; Asprey, L. B. Anal. Chem. 1957, 29, 856-7.
(13) SADABS, Bruker Nonius area detector scaling and absorption
correction, V2.05; Bruker-AXS Inc.: Madison, WI, 2003.
(14) Sheldrick, G. M. SHELXS86, Program for the Solution of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1986.
(15) Sheldrick, G. M. SHELXL97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(16) (a) Johnson, C. K. ORTEP II; Report ORNL-5138; Oak Ridge National
Laboratory: Oak Ridge, TN, 1976. (b) Zsolnai, L. XPMA and
ZORTEP, Programs for InteractiVe ORTEP Drawings; University of
Heidelberg: Heidelberg, Germany, 1997.
Inorganic Chemistry, Vol. 43, No. 20, 2004 6309

Banerjee et al.
with the lanthanide contraction accounting for the decrease
upon traversing the series from La to Gd (Table 2). In
contrast, Ln-F bonds vary in a discontinuous fashion: there
is at first a statistically equal set of distances noted from La
to Ce to Nd, before a small but steady increase in Ln-F(1)
bond length from Nd to Sm, and finally a more dramatic
increase at Gd. Pure compounds with lanthanides heavier
than Gd were not obtained.
Both cations and anions have intermolecular π-π interac-
tions for adjacent pairs of SC6F5 ligands that generate an
anion that is flattened on two sides. For the cations, this
placement of ligands results in a rather polar molecular spe-
cies, in contrast to the anion, which contains near inversion
symmetry. The flattened molecular shape lends itself to low-
dimensional stacking of ions in the crystal structure. For the
[(DME)3Ln(SC6F5)2]2[Hg2(SC6F5)6] salts, as in other molec-
ular salts, this also gives rise to segregated 2D sheets of
cations that alternate with sheets of anions in the solid state.
Further, the anions form infinite chains of directly overlap-
ping pairs of SC6F5 ligands between adjacent ions. These
chains criss-cross along the crystallographic a and b direc-
tions for the inversion-related pairs of SC6F5 ligands in the
anion to yield a tightly woven 2D sheet of closely interacting
anions. Although the a and b axes differ significantly in
length, there is no crystallographic distinction between pairs
of terminal SC6F5 ligands of the anion, since inversion
symmetry is imposed on the anion by the space group. As a
result, the geometry of the intermolecular π-π interactions
along the a versus b directions is approximately the same.
This situation accommodates the 50:50 disorder for two sites
for each of these terminal SC6F5 ligands in the anion, in
contrast to the ordered cation. The packing motif for the
cations leads to an ordered, but lower dimensional, stacking
array, as the cations pair up to form discrete dimers with
one intramolecular and two intermolecular π-π interactions.
The one DME solvate molecule per Ln is found in the cation
sheet, filling a void between cation pairs at the interface to
the anion sheet.
Figure 1. Molecular structure of the cation (a) and dianion (b) in
[(DME)3Ln(SC6F5)2]2[Hg2(SC6F5)4(µ2-SC6F5)2]. Thermal ellipsoids are
drawn at the 50% probability level for the Pr compound.
compounds can be prepared either by combining solutions
of Ln and Hg reagents or by in situ generation of the Ln
reagent in the presence of excess Hg(SC6F5)2 (reaction 1).
They are insoluble in apolar solvents (i.e., hexane, toluene)
but redissolve in Lewis bases such as pyridine, acetonitrile,
or THF. Once isolated, they are relatively stable in air and
can be handled briefly with no immediate loss of crystallinity.
Attempts to prepare the analogous Eu(III) derivative led only
to the isolation of divalent [Eu(SC6F5)2]n,10a and the later
(heavier) lanthanides do not appear to form isolable com-
pounds.
Discussion
While the SC6F5 moiety has, until now, provided an entry
into hydrocarbon soluble molecular and cluster chemistry
of the lanthanides, compounds 1-6 are soluble only in Lewis
base solvents. Molecular Ln(II) and Ln(III) compounds10
routinely dissolved in aromatic solvents such as toluene, and
even the chalcogen rich (THF)6LnE(EE)4(SC6F5)2 clusters,8
which had only two SC6F5 ligands to solubilize four Ln
centers, were toluene soluble. Presumably, the unusual in-
solubilities of 1-6 originate from the ionic nature of the
products. Previously, 1D structures had been noted, i.e.,
Eu(SC6F5)2,10a where pairs of bridging thiolates connected
adjacent Eu ions and π-π interactions connecting neighbor-
ing sets of SC6F5 ligands. Even though Eu(SC6F5)2 formed
a polymeric lattice, the compound itself dissolved in apolar
solvents. Compounds 1-6, with 2D sheets of anions isolating
the layers of Ln containing cations, represent the first set of
Ln compounds with SC6F5 ligands that are totally insoluble
in hydrocarbon solvents. The large molecular dipole of the
Ln(SC6F5)3 + Hg(SC6F5)2 DME8
[(DME)3Ln(SC6F5)2]2[Hg2(SC6F5)6] 7DME
2Ln + 5Hg(SC6F5)2 (1)
Low-temperature single-crystal X-ray diffraction analyses
of 1-6 were obtained, revealing an isostructural series of
solvated Ln cations with mercury dianions. Figure 1 gives
an ORTEP diagram for the Pr derivative as a generic struc-
ture of 1-6, and Table 2 gives a listing of significant bond
lengths and angles in the complexes. In all compounds, the
Ln ions are each chelated by three bidentate DME ligands
distributed on one side of the metal. There are two terminal
thiolates on the other side, one of which also coordinates to
the Ln through a dative bond to the ortho fluoride F(1). The
Ln-S and Ln-O bond lengths vary with Ln ionic radius,
6310 Inorganic Chemistry, Vol. 43, No. 20, 2004

Ln/Hg Compounds with Fluorinated Thiolate Ligands
Table 2. Significant Distances (Å) and Angles (deg) for 1-6
La
Ce
Pr
Nd
Sm
Gd
Ln(1)-O(2)
Ln(1)-O(6)
Ln(1)-O(4)
Ln(1)-O(1)
Ln(1)-O(3)
Ln(1)-O(5)
Ln(1)-F(1)
Ln(1)-S(2)
Ln(1)-S(1)
2.563(3)
2.578(2)
2.617(3)
2.586(2)
2.601(2)
2.640(3)
2.797(2)
2.8935(10)
2.9277(9)
2.547(3)
2.548(3)
2.590(4)
2.570(3)
2.598(3)
2.626(3)
2.811(3)
2.8692(12)
2.9034(11)
2.528(2)
2.536(2)
2.552(3)
2.546(2)
2.569(2)
2.604(3)
2.799(2)
2.8431(8)
2.8807(8)
2.512(4)
2.524(4)
2.545(5)
2.526(4)
2.554(5)
2.592(5)
2.801(4)
2.8316(18)
2.8656(17)
2.475(4)
2.486(4)
2.496(5)
2.496(4)
2.535(4)
2.562(4)
2.813(3)
2.8011(15)
2.8307(14)
2.459(3)
2.465(3)
2.483(3)
2.480(3)
2.515(3)
2.554(3)
2.837(3)
2.7909(10)
2.8171(10)
Ln-S(1)-C(1)
Ln-S(2)-C(7)
108.1(1)
110.1(1)
108.3(2)
111.4(2)
108.7(1)
112.1(1)
108.5(3)
112.5(2)
109.1(2)
113.2(2)
109.9(2)
114.0(1)
Ln containing cations must also play a role in the insolubility
of 1-6.
discrete heterometallic thiolate, namely [(py)3EuHg(SPh)4]2,
be isolated by dissolving the product in a stronger Lewis
base.4 Unfortunately, with the SC6F5 ligand a crystalline
heterometallic product was obtained only from DME. Still,
the fact that both heterometallic SPh and SC6F5 compounds
are so dramatically less soluble than their monometallic
components suggests that SPh ligands are also being
abstracted from Ln.
One distinct difference in the chemistry of heterometallic
SPh and SC6F5 compounds is noted in a thermolysis
experiment. While Ln(C6F5)3 compounds have already been
shown to decompose thermally to give LnF3,10 it was unclear
whether the ionic configurations of 1-6 would have any im-
pact on the identity of the thermolysis products, and so an
analysis of the thermal decomposition of 4 was undertaken.
In contrast to the thermolysis of heterometallic Ln/Hg SPh
compounds,4 which gave mixtures of LnS and HgS, decom-
position of 4 gave only solid-state NdF3, with the mercury
fluorothiolate subliming into the cold zone of the thermolysis
experiment prior to decomposition (reaction 2).
Still, solid-state structure is not necessarily identical to
solution structure. 19F NMR analyses in THF and acetonitrile
give some information regarding structure in solution. In
acetonitrile, the compounds show only a single set of ortho,
meta, and para F resonances, suggesting either that the
solution state contains only a single type of SC6F5 environ-
ment, or that there is fast site exchange that averages the
inequivalent mercury bonding environments (terminal and
bridging) with those of the terminal and chelating lanthanide
thiolates. In THF, the La compound again shows only a
single resonance for the meta and para fluorides, but the ortho
resonance is split 3:1, which suggests that there are distinct
Ln versus Hg containing molecular ions in THF solution,
and that site exchange between Ln and Hg thiolates is slow
on the NMR time scale. The molecular form of the anions
is not defined by the NMR experiment, but the tendency of
Hg2(SR)62- to convert to Hg(SR)3- in neutral donor solvents
is well-known.17 Mass spectra for the La and Pr compounds
in acetonitrile were obtained, and the negative ion spectra
contained a series of identifiable peaks, including SC6F5 (M-
[(DME)3Nd(SC6F5)2]2[Hg2(SC6F5)6] 9
∆8
-
) 199.6), Hg(SC6F5)3- (M- ) 798.7), (CH3CN)Hg(SC6F5)3
NdF3 + Hg(SC6F5)2 + (SC6F4)n (2)
-
(M- ) 837.2), and Hg2(SC6F5)5 (M- ) 1393.9), with
The mercury dianion is distinctly distorted from ideal
tetrahedral Hg(II) geometries. Although the inner Hg2S2 cores
are crystallographically required to be planar (which still
allows for tetrahedral symmetry), the bridging ligands show
no evidence of disorder, the average S-Hg-S′ angles and
average Hg-S-Hg′ angles are within a degree of 90° and
sum to approximately 180° for 1-6. This distortion from
tetrahedral geometry (i.e., 109.5° angles) and planarity is
relative intensities of 1:20:7:14. Clearly, the structure in
solution is more complicated than that in the solid state.
Previous studies have shown that elemental S will displace
SPh but not SC6F5 from lanthanide coordination spheres Ln-
(ER)3, which implies that Ln-S(C6F5) bonds are chemically
more robust than are Ln-S(Ph) bonds in redox reactions.7
This, coupled with earlier work that found no absolute
evidence for Hg(II) promoted abstraction of SPh from Ln
coordination spheres, led to the mistaken assumption that
LnHg(SC6F5)x compounds would also adopt molecular, rather
than ionic, structures.
Clearly, a number of factors are influencing these differ-
ences in reactivity. Presumably, the different strengths of
the formed disulfide linkages are important in the redox
work, but solvent effects are also both possible and intangible
in the heterometallic chemistry, given that parallel experi-
ments with SPh and SC6F5 did not yield interpretable results.
Heterometallic syntheses with SPh ligands in THF always
produced insoluble, essentially intractable products at room
temperature and pressure, and only with Eu(II) could a
2-
observed also in the related Hg2(SPh)6 (89.5° and 90.5°,
respectively, for S-Hg-S and Hg-S-Hg),18 even though
the latter compound does not display significant inter- or
intramolecular π-π interactions between SPh ligands. A
related anion, Hg2(SMe)62-, contains a mercury-sulfur core
that also has Hg geometries that are far from tetrahedral
(S-Hg-S, 94.2°).19 Disorder within the dianion in 1-6
complicates an analysis of the Hg-S bond lengths beyond
the above, but all refined to values within the normal range
of Hg-S interactions.
(18) Bowmaker, G. A.; Dance, I. G.; Harris, R. K.; Henderson, W.; Laban,
I.; Scudder, M. L.; Oh, S.-W. J. Chem. Soc., Dalton Trans. 1996,
2381.
(19) Bowmaker, G. A.; Dance, I. G.; Dobson, B. C.; Rogers, D. A. Aust.
J. Chem. 1984, 37, 1607.
(17) Henkel, G.; Krebs, B. Chem. ReV. 2004, 104, 801-24
Inorganic Chemistry, Vol. 43, No. 20, 2004 6311

Banerjee et al.
Within a given cation, interplanar distances increase
slightly on going from the more interior contacts, at 3.2 Å,
and for the more exterior contacts, at 3.8 Å. This increase
in contact distances is consistent with the inflexibility asso-
ciated with the bidentate [e.g., S(1)-Ln-F(1)] ligand and
the flexibility of the adjacent monodentate [e.g., S(2)-Ln]
ligand. Within the anions, the dihedral angle between ad-
jacent terminal C6F5 rings is also not zero. However, the
contact distances decrease on going from the more interior
3.6 Å contacts to the more exterior 3.2 Å contacts. This
decrease in contact distances is consistent with the type of
nontetrahedral disorder observed for the Hg coordination.
These distances, 3.6 Å on the interior and 3.2 Å on the
exterior, are observed for the entire series here, 1-6. As for
intermolecular ring-ring contacts, there are none for the
isolated cations, but the disorder in the terminal ligands of
the anion allows for two sets of contact distances between
parallel rings that are crystallographically equivalent, namely,
A‚‚‚B and B‚‚‚A. For all anions in complexes 1-6, the
intermolecular separation between nearest neighbor rings is
parallel at a 3.5 Å separation. This is expected for closely
stacking rings that are related by a symmetry center, as found
in the 2D array of anions here.
Finally, this isostructural series presents a unique op-
portunity to evaluate the manner by which steric demands
impact dative Ln-F bond lengths. From the distances in
Table 2, it becomes clear that these Ln-F interactions are
influenced by more than just the ionic radii of Ln and F.
The six Ln-O and two Ln-S bonds all behave as expected,
gradually contracting as the size of Ln decreases with the
lanthanide contraction.20 This gradual decrease serves to
increase interligand repulsive interactions, and the bond most
sensitive to these repulsions is Ln-F, the weakest bond
within the primary Ln coordination sphere. In the early
compounds 1-3, there are no significant differences in Ln-F
bond lengths, which range from La-F (2.797(2) Å) to
Nd-F (2.801(4) Å) and are compared to distances
noted, for example, in [(THF)3Ce(SC6F5)3]2 (2.749(2) Å) and
(py)4Sm(SC6F5)3 (2.703(5) Å).10b As the series progresses,
there is a small but constant increase in the distance
separating Ln and F. With Ln ionic radii decreasing from 1
to 6 (La ) 1.30 Å; Gd ) 1.19 Å),20 the increase in Ln-F
separation from Nd (2.801(4) Å) to Gd (2.837(3) Å) must
be originating from interligand repulsive interactions that
increase as the entire Ln coordination sphere contracts.
Support for this steric interpretation is found in the series
of Ln-S-C angles, which increase as the series progresses
from La to Gd (see Table 2). The nonchelating S(2) ligand
is affected more, with Ln-S(2)-C(7) increasing from 110.1-
(1)° (La) to 114.0(1)° (Gd). In the chelating thiolate, this
opening of Ln-S(1)-C(1) is significant only for Gd, much
as was found in the series of Ln-F distances. The inability
to isolate compounds with Ln smaller than Gd could be
resulting from a change in molecular conformation as the
Ln-F interaction becomes unsustainable.
Conclusion
Lanthanide and mercury benzenefluorothiolates react to
form stable, relatively insoluble heterometallic compounds
with transfer of thiolate from Ln to Hg. This anion transfer
persists in solution. Contributing to the stability of the
observed solid-state structure is an extensive network of π-π
interactions that connect anions with both cations and
neighboring anions. The dative Ln-F bond lengths in the
structures do not vary with Ln ionic radius.
Acknowledgment. This work was supported by the
National Science Foundation under Grant CHE-0303075.
Supporting Information Available: X-ray crystallographic files
in CIF format for the crystal structures of 1-6. This material is
available free of charge via the Internet at http://pubs.acs.org.
(20) Shannon, R. D. Acta Crystallogr., Sect. A 1976, 32, 751.
IC049215Q
6312 Inorganic Chemistry, Vol. 43, No. 20, 2004