Trivalent lanthanide compounds with fluorinated thiolate ligands: Ln-F dative interactions vary with Ln and solvent

Article abstract of DOI:10.1021/ic0104813

The fluorinated tris-thiolate compounds Ln(SC₆F₅)₃ can be isolated as THF, pyridine, or DME coordination complexes. In THF, the larger Ce forms dimeric [(THF)₃Ce(SC₆F₅)₃]₂ (1) with bridging thiolate ligands, while the smaller lanthanides (Ln = Ho (2), Er (3)) form monometallic (THF)₃Ln(SC₆F₅)₃ compounds. There is a tendency for fluoride to coordinate to Ln throughout the lanthanide series (Ce-Er). The cerium compound 1 contains a pair of bridging thiolates connecting two eight-coordinate Ce(III) ions. Of the two terminal thiolates, only one exhibits a distinct Ce-F bond. In contrast, the Ho derivative (THF)₃Ho(SC₆F₅)₃ is a molecular compound in the solid state, with two monodentate thiolates and one thiolate that again coordinates through both S and F atoms. Incorporation of a stronger Lewis base reduces but does not necessarily eliminate the tendency to form Ln-F bonds. Structural characterization of the eight-coordinate (pyridine)₄Sm(SC₆F₅)₃ (4) reveals a single, clearly defined Ln-F interaction, while in (pyridine)₄Yb-(SC₆F₅)₃ (5) there are no Yb-F bonds. In the structure of (DME)₂Er(SC₆F₅)₃ (6) the DME ligands completely displace F from the Er coordination sphere.

Full text of DOI:10.1021/ic0104813

Inorg. Chem. 2002, 41, 28−33
Trivalent Lanthanide Compounds with Fluorinated Thiolate Ligands:
Ln−F Dative Interactions Vary with Ln and Solvent
Jonathan H. Melman, Christa Rohde, Thomas J. Emge, and John G. Brennan*
Department of Chemistry, Rutgers, the State UniVersity of New Jersey, 610 Taylor Road,
Piscataway, New Jersey 08854-8087
Received May 8, 2001
The fluorinated tris-thiolate compounds Ln(SC F ) can be isolated as THF, pyridine, or DME coordination complexes.
6
5 3
In THF, the larger Ce forms dimeric [(THF)3Ce(SC F ) ] (1) with bridging thiolate ligands, while the smaller lanthanides
6
5 3 2
(Ln ) Ho (2), Er (3)) form monometallic (THF)3Ln(SC F ) compounds. There is a tendency for fluoride to coordinate
6
5 3
to Ln throughout the lanthanide series (Ce−Er). The cerium compound 1 contains a pair of bridging thiolates
connecting two eight-coordinate Ce(III) ions. Of the two terminal thiolates, only one exhibits a distinct Ce−F bond.
In contrast, the Ho derivative (THF)3Ho(SC F ) is a molecular compound in the solid state, with two monodentate
6
5 3
thiolates and one thiolate that again coordinates through both S and F atoms. Incorporation of a stronger Lewis
base reduces but does not necessarily eliminate the tendency to form Ln−F bonds. Structural characterization of
the eight-coordinate (pyridine)4Sm(SC F ) (4) reveals a single, clearly defined Ln−F interaction, while in (pyridine)4Yb-
6
5 3
(SC F ) (5) there are no Yb−F bonds. In the structure of (DME)2Er(SC F ) (6) the DME ligands completely displace
6
5 3
6 5 3
F from the Er coordination sphere.
Introduction
Coordination of organofluoride ligands to metal ions is
an unusual phenomenon.4 Because of the weak, highly ionic
nature of the M-F dative interaction, less electropositive
metals (i.e., Hg, Pt) do not tend to form such bonds. With
more electropositive metals there is a pronounced tendency
either to have such bonds displaced by more strongly basic
lone pairs or to engage in a C-F bond activation process
that yields a metal fluoride compound.4,5 The latter process
is particularly prevalent in divalent Ln chemistry, where
fluoride abstraction leads to oxidation of the Ln and the
formation of fluoride compounds with a variety of ancillary
ligands,5 but activation of C-F bonds has also been noted
in the thermal decomposition of the fluorinated thiolates.3
As F coordination is presumably the first step in this C-F
bond cleavage process, an understanding of dative Ln-F
interactions would be helpful in developing new synthetic
methods in organofluorine chemistry.
Of the numerous lanthanide compounds containing flu-
orinated ligands that have been investigated for potential
CVD applications,1-3 there have been two reports2,3 describ-
ing the synthesis of lanthanide compounds with organofluo-
rine ligands that contain dative Ln-F interactions. Com-
pounds with fluorinated amido ligands2 were first communi-
cated, and the dative Ln-F bonds noted in the solid state
were found to be particularly susceptible to displacement
by stronger Lewis base solvents. In contrast, with the more
recently described fluorinated thiolate compounds, structural
characterization of both divalent and trivalent Ln(SC6F5)x (x
) 2, 3) revealed that even in the presence of THF donors
there were clear Ln-F interactions.3 It was presumed that
the geometric constraints imposed by the nearly 90° Ln-
S-C angles in the thiolate compounds and the importance
of π stacking among the ligands were responsible for more
pervasive Ln-F bonding in the thiolates.
(4) (a) Plenio, H. Chem. ReV. 1997, 97, 5553. (b) Murphy, E. F.;
Murugavel, R.; Roesky, H. W. Chem. ReV. 1997, 97, 3425. (c)
Kulawiec, R. J.; Crabtree, R. H. Coord. Chem. ReV. 1990, 99, 89. (d)
Arroyo, M.; Bernes, S.; Brianso, J. L.; Mayoral, E.; Richards, R. L.;
Ruis, J.; Torrens, H. J. Organomet. Chem. 2000, 599, 170.
* Author to whom correspondence should be addressed. E-mail: bren@
rutchem.rutgers.edu.
(1) (a) Malandrino, G.; Incontro, O.; Castelli, F.; Fragala`, I. L.; Benelli,
C. Chem. Mater. 1996, 8, 1292. (b) Plakatouras, J. C.; Baxter, I.;
Hursthouse, M. B.; Abdul Malik, K. M.; McAleese, J.; Drake, S. R.
J. Chem. Soc., Chem. Commun. 1994, 2455.
(2) Click, D. R.; Scott, B. L.; Watkin, J. G. Chem. Commun. 1999, 633.
(3) Melman, J. H.; Emge, T. J.; Brennan, J. G. Inorg. Chem. 2001, 40,
1078.
(5) (a) Deacon, G. B.; Meyer, G.; Stellfeldt, D. Eur. J. Inorg. Chem. 2000,
1061. (b) Deacon, G. B.; Harris, S. C.; Meyer, G.; Stellfeld, D.;
Wilkinson, D. L.; Zelesny, G. J. Organomet. Chem. 1998, 552, 165.
(c) Watson, P. L.; Tulip, T. H.; Williams, I. Organometallics 1990,
9, 1999. (d) Burns, C. J.; Berg, D. J.; Andersen, R. A. J. Chem. Soc.,
Chem. Commun. 1987, 272. (e) Burns, C. J.; Andersen, R. A. J. Chem.
Soc., Chem. Commun. 1989, 136.
28 Inorganic Chemistry, Vol. 41, No. 1, 2002
10.1021/ic0104813 CCC: $22.00 © 2002 American Chemical Society
Published on Web 12/06/2001

TriWalent Ln Compounds with Fluorinated Thiolate Ligands
Synthesis of (THF)3Er(SC6F5)3 (3). As for 1 above, Er (0.191
g, 1.14 mmol) and Hg(SC6F5)2 (1.02 g, 1.71 mmol) in THF (ca. 30
mL) gave mercury (0.33 g, 97%) and pink crystals (0.396 g, 35%)
that become opaque at 100 °C, begin to darken at 170 °C, and turn
black by 328 °C. IR: 2945 (s), 2875 (s), 1505 (m), 1462 (s), 1378
(s), 1301 (w), 1264 (w), 1173 (w), 1124 (w), 1083 (m), 1070 (m),
1006 (m), 967 (m), 927 (w), 859 (m), 724 (w), 670 (w), 620 (w)
cm-1. Unit cell (Mo KR, 153 K): space group P21/n, a ) 12.03(1)
Å, b ) 22.13(1) Å, c ) 12.65(1) Å, â ) 97.54(7)°, Z ) 4, V )
3339(4) Å3. UV-vis (THF): 367 (2.5), 380 (37), 385 (14), 490
(1.6) 522 (19), 654 (1.3). Anal. Calcd for C30H24ErF15O3S3: C,
36.7; H, 2.47. Found: C, 36.7; H, 2.52. 19F NMR (24 °C, OC4D8):
-161.4 (1F, w1/2 ) 49 Hz), -152.8 (2F, w1/2 ) 62 Hz), -96.3
(2F, w1/2 ) 645 Hz). When heated at 220 °C under vacuum, the
compound eliminates white crystalline material that was identified
as a mixture of (C6F2S)2 and (C6F4S)n (n ) 2, 3) by DP-EI-MS.
XRPD identified ErF3 as the only crystalline Er product.
Synthesis of (py)4Sm(SC6F5)3‚1/2py (4). As for 1, Sm (0.215 g,
1.43 mmol) and Hg(SC6F5)2 (1.29 g, 2.16 mmol) in pyridine (10
mL) gave mercury (0.39 g, 93%) and, when cooled (5 °C), yellow
crystals (0.325 g, 35%) that start turning red at 60 °C, show some
signs of melting at 64 °C, and start turning black at 105 °C. IR:
2924 (s), 2855 (s), 1512 (m), 1498 (s), 1465 (s), 1378 (m), 1261
(m), 1090 (s), 1021 (m), 967 (m), 921 (w), 899 (w), 866 (m), 841
(w), 805 (m), 751 (w), 724 (w), 701 (m), 673 (w), 663 (w), 623
(w) cm-1. UV-vis (toluene) shows only the visible tail of a UV
absorption. Anal. Calcd for C40.5H22.5F15N4.5S3Sm1: C, 44.1; H,
2.05; N, 5.71. Found: C, 44.5; H, 2.38; N, 6.30. 19F NMR (OC4D8,
24 °C): -132.5 (2F, w1/2 ) 69 Hz), -161.9 (1F, w1/2 ) 74 Hz).
Synthesis of Yb(SC6F5)3(pyr)4‚pyr‚THF (5). Yb (0.214 g, 1.24
mmol) and Hg(SC6F5)2 (1.109 g, 1.855 mmol) were combined in
THF (ca. 25 mL). The solution was stirred until the metal was
consumed, and only mercury was visible on the bottom of the
reaction mixture (ca. 1 day). The red solution was filtered, pyridine
(5 mL, 60 mmol) was added, and the mixture was layered with 20
mL of hexane and cooled to 5 °C to give red-orange crystals (1.357
g, 88%) that turn red and melt between 79 and 84 °C. Above 135
°C the liquid deposits a yellow-orange solid that darkens at 169
°C. IR: 2926 (s), 2857 (s), 1604 (m), 1504 (m), 1464 (s), 1378
(s), 1264 (w), 1223 (m), 1157 (w), 1072 (m), 1040 (w), 1006 (m),
968 (m), 916 (w), 859 (m), 758 (m), 701 (m), 626 (w) cm-1. UV-
vis (pyr): 440 nm (273 M-1 cm-1), with a shoulder at 400 nm.
Anal. Calcd for C47H33YbF15OS3: C, 45.6; H, 2.69; N, 5.66.
Found: C, 44.6; H, 2.58; N, 5.57. 19F NMR (C6D6, 24 °C): -108.7
In this manuscript we outline the effect of neutral donor
and Ln size on the tendency of Ln(SC6F5)3 to form dative
Ln-F interactions. THF coordination compounds of
Ce(SC6F5)3, Ho(SC6F5)3, Er(SC6F5)3, pyridine compounds of
Sm(SC6F5)3 and Yb(SC6F5)3, and a DME coordination
complex of Er(SC6F5)3 are all examined in an effort to
understand how the steric and electronic properties of neutral
donors influence the Ln-F interaction.
Experimental Section
General Methods. All syntheses were carried out under ultrapure
nitrogen (JWS), using conventional drybox or Schlenk techniques.
Solvents (Fisher) were refluxed continuously over molten alkali
metals or K/benzophenone and collected immediately prior to use.
Anhydrous pyridine (Aldrich) was purchased and refluxed over
KOH. Hg(SC6F5)23,6 was prepared according to literature procedure.
Ln and Hg were purchased from Strem. HSC6F5 was purchased
from Aldrich. Melting points were taken in sealed capillaries and
are uncorrected. IR spectra were taken on a Mattus Cygnus 100
FTIR spectrometer and recorded from 4000 to 450 cm-1 as a Nujol
mull on KBr plates. Electronic spectra were recorded on a Varian
DMS 100S spectrometer with the samples in a 1.0 mm or a 1.0 cm
quartz cell attached to a Teflon stopcock. Molar absorptivities (ꢀ)
are included in parentheses. Elemental analyses were performed
by Quantitative Technologies, Inc. (Whitehouse, NJ). 19F NMR and
1H NMR spectra were obtained on a Varian Gemini 400 MHz NMR
spectrometer, and chemical shifts are reported in δ (ppm). All
products are unstable at room temperature for extended periods
when dissolved in DME or pyridine.
Synthesis of [(THF)3Ce(SC6F5)3]2 (1). Ce (0.176 g, 1.26 mmol)
and Hg(SC6F5)2 (1.13 g, 1.89 mmol) were combined in THF (20
mL), and the mixture was stirred until the chunks of metal were
consumed and elemental mercury was visible in the bottom of the
flask (overnight). The pale yellow solution was filtered away from
the mercury (0.32 g, 84%), reduced in volume under vacuum to
ca. 15 mL, and layered with hexane (15 mL) to give colorless
crystals (0.732 g, 61%) which turn an opaque white at 93 °C, melt
at 217-226 °C, appear to eliminate a gas at 278 °C, begin to darken
at 297 °C, and continue to darken up to 350 °C. IR: 2923 (s),
2854 (s), 1502 (m), 1464 (s), 1378 (m), 1317 (w), 1299 (w), 1262
(w), 1171 (w), 1139 (w), 1126 (w), 1079 (m), 1069 (m), 1009 (m),
971 (m), 921 (w), 859 (m), 748 (w), 723 (w), 664 (w) cm-1. UV-
vis (THF): no absorption maxima, but slow diffusion of air into
the sample gave an absorption centered at 430 nm (ꢀ > 200 (M
cm)-1). Anal.Calcd for C60H48Ce2F30O6: C, 37.8; H, 2.54. Found:
C, 37.0; H, 2.50. 19F NMR (OC4D8, 24 °C): -131.4 (2F, d, J ) 20
Hz), -148.4 (2F, t, J ) 21 Hz), -159.9 (1F, t, J ) 21 Hz).
Synthesis of (THF)3Ho(SC6F5)3 (2). As for 1 above, Ho (0.244
g, 1.48 mmol) and Hg(SC6F5)2 (1.327 g, 2.219 mmol) in THF (ca.
25 mL) gave mercury (0.37 g, 82%) and pink crystals (0.373 g,
26%) that turn white and appear to lose solvent at 183 °C, melt
between 217 and 240 °C, and appeared to eliminate a gas at 273
°C. IR: 2947 (s), 2871 (s), 1504 (m), 1462 (s), 1378 (s), 1300 (w),
1262 (w), 1173 (w), 1125 (w), 1083 (m), 1069 (m), 1039 (w), 1006
(m), 967 (m), 925 (w), 895 (w), 859 (m), 723 (w), 669 (w), 619
(w) cm-1. UV-vis (in THF): 362 (18), 421 (5.1), 451 (68), 457
(29), 462 (24), 539 (3.6), 552 (2.2), 642 (1.8). Anal. Calcd for
ppm (2F, w1/2 ) 252 Hz), -160.0 ppm (2F, w1/2 ) 95 Hz), -160.9
1
(1F, w1/2 ) 95 Hz). H NMR (C6D6, 24 °C): 8.60 (10H, w1/2
)
193 Hz), 4.01 (4H, w1/2 ) 101 Hz), 1.57 (4H, w1/2 ) 28 Hz).
Assignments of the proton resonances were deduced by addition
of THF or pyridine. There is no change in the 19F NMR spectrum
upon addition of sulfur to the NMR tube. When dissolved in
pyridine or DME, 5 decomposes thermally at room temperature to
give a colorless solution and a light yellow, insoluble precipitate.
Synthesis of (DME)2Er(SC6F5)3 (6). As for 1 above, Er (0.193
g, 1.15 mmol) and Hg(SC6F5)2 (1.035 g, 1.731 mmol) in DME
(ca. 20 mL) gave mercury (0.30 g, 87%) and pink crystals (0.827
g, 73%) that turn yellow at 79 °C, melt and turn orange at 215 °C,
and blacken at 257 °C. IR: 2923 (s), 2854 (s), 1506 (m), 1465 (s),
1378 (m), 1260 (m), 1189 (w), 1084 (m), 1075 (m), 1030 (m), 986
C30H24F15HoO3S3: C, 36.8; H, 2.47. Found: C, 36.3; H, 2.42. 19
F
(w), 967 (m), 907 (w), 866 (m), 856 (m), 803 (w), 722 (w) cm-1
.
NMR (OC4D8, 24 °C): -179.6 (2 F, w1/2 ) 76 Hz), -181.5 (1 F,
w1/2 ) 53 Hz). There was no change in line shape as a function of
temperature.
UV-vis (THF): 367 (2.5), 380 (27), 490 (1.3), 522 (15), 653 (1.0).
Anal. Calcd for C26H20ErF15O4S3: C, 33.0; H, 2.13. Found: C,
32.5; H, 1.94. The 19F NMR (C6D6, 24 °C) resonances could not
be located.
(6) Peach, M. E. J. Inorg. Nucl. Chem. 1973, 35, 1046.
Inorganic Chemistry, Vol. 41, No. 1, 2002 29

Melman et al.
Table 1. Summary of Crystallographic Details for 1, 2, and 4-6
1
2
4
5
6
empirical formula
fw
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C30H24CeF15O3S3
953.79
P1h
C30H24F15HoO3S3
978.60
P21/n
12.004(5)
22.247(11)
12.697(4)
90.00
97.71(3)
90.00
3360(2)
4
1.934
-120
0.71073
2.658
0.024
0.054
C40.5H22.5F15N4.5S3Sm
1103.66
P1h
C47H33F15N5OS3Yb
1238.00
P21/n
11.513(7)
31.499(8)
14.144(5)
90.00
112.23(4)
90.00
4748(4)
4
1.732
-120
0.71073
2.204
0.024
0.056
C26H20ErF15O4S3
944.86
C2/c
33.071(7)
8.9410(15)
21.544(3)
90.00
90.46(1)
90.00
6370(2)
8
1.970
-120
0.71073
2.953
0.025
0.063
11.055(5)
12.377(5)
13.216(6)
71.77(3)
76.36(4)
84.90(3)
1669(1)
2
1.898
-120
0.71073
1.669
9.510(3)
14.644(5)
15.911(9)
108.96(4)
92.21(3)
95.00(3)
2082(1)
2
1.760
-120
0.71073
1.665
Z
D(calcd) (g/cm-3
temp (°C)
λ (Å)
)
abs coeff (mm-1
)
R(F)a [I > 2σ(I)]
0.029
0.073
0.056
0.112
Rw(F2)a [I > 2σ(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.
Figure 2. ORTEP diagram of (THF)3Ho(SC6F5)3 (2). Thermal ellipsoids
are drawn at the 50% probability level.
Figure 1. ORTEP diagram of [(THF)3Ce(SC6F5)3]2 (1). Thermal ellipsoids
are drawn at the 50% probability level.
corresponding trivalent thiolates in 26-88% isolated, crystal-
line yields (reaction 1). Colorless [(THF)3Ce(SC6F5)3]2 (1)
X-ray Structure Determination of 1, 2, and 4-6. Data for 1,
2, and 4-6 were collected on an Enraf-Nonius CAD4 diffractometer
with graphite-monochromatized Mo KR radiation (λ ) 0.71073
Å) at -120 °C. The three check reflections, measured every hour,
showed less than 2% intensity variation. The data were corrected
for Lorentz effects and polarization, and absorption, the latter by a
numerical (SHELX76)7 method. The structures were solved by
direct methods (SHELXS86).8 All non-hydrogen atoms were refined
(SHELXL97)9 based upon Fobs2. All hydrogen atom coordinates
were calculated with idealized geometries. Scattering factors (fo,
f ′, f ′′) are as described in SHELXL97. Crystallographic data and
final R indices for 1, 2, and 4-6 are given in Table 1. Significant
bond distances and angles for 1, 2, and 4-6 are given in the figure
captions. Complete crystallographic details are given in the Sup-
porting Information. ORTEP diagrams10 for 1, 2, and 4-6 are
shown in Figures 1-5, respectively.
2Ln + 3Hg(SC6F5)2 solvent8 2(solvent)xLn(SC6F5)3 + 3Hg
(1)
is a dimer, with a pair of bridging thiolates connecting two
eight-coordinate Ce(III) ions, with four sulfur atoms, three
oxygen atoms, and one fluorine atom comprising the primary
coordination sphere. Figure 1 shows an ORTEP diagram of
1, and Table 2 gives a listing of significant bond distances
and angles for 1. The shortest Ce-F separation is the 2.749-
(2) Å dative interaction between Ce and F(10), and there
are π-π interactions between the S(2) and S(3) thiolates,
as in Figure 1. With smaller Ln, there is an increasing
tendency to form monometallic structures. The THF deriva-
tives of both Ho(SC6F5)3 (2) and Er(SC6F5)3 (3) are iso-
structural, and a complete structural analysis of the Ho
compound (THF)3Ho(SC6F5)3 reveals a pentagonal bipyra-
midal product with two axial thiolates and one equatorial
thiolate. The structure of 2 is shown in Figure 2, and
Results
Transmetalation reactions of Ln (Ln ) Ce, Sm, Ho, Er,
Yb) with Hg(SC6F5)2 in THF, pyridine, or DME give the
(7) Sheldrick, G. M. SHELX76, Program for Crystal Structure Determi-
nation; University of Cambridge: Cambridge, England, 1976.
(8) Sheldrick, G. M. SHELXS86, Program for the Solution of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1986.
(9) Sheldrick, G. M. SHELXL97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(10) (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.
30 Inorganic Chemistry, Vol. 41, No. 1, 2002

TriWalent Ln Compounds with Fluorinated Thiolate Ligands
Table 2. Bond Lengths (Å) and Angles (deg) for [(THF)3Ce(SC6F5)3]2
Ce(1)-O(3)
Ce(1)-F(10)
Ce(1)-S(1)
Ce(1)-O(1)
2.509(3)
2.749(2)
3.0089(16)
2.516(3)
Ce(1)-S(3)
Ce(1)-S(1)′
Ce(1)-O(2)
Ce(1)-S(2)
2.8567(17)
3.0381(19)
2.554(3)
2.8696(16)
O(3)-Ce(1)-O(1)
O(1)-Ce(1)-O(2)
O(1)-Ce(1)-F(10)
O(3)-Ce(1)-S(3)
O(2)-Ce(1)-S(3)
O(3)-Ce(1)-S(2)
O(2)-Ce(1)-S(2)
S(3)-Ce(1)-S(2)
O(1)-Ce(1)-S(1)
F(10)-Ce(1)-S(1)
S(2)-Ce(1)-S(1)
O(1)-Ce(1)-S(1)′
F(10)-Ce(1)-S(1)′
S(2)-Ce(1)-S(1)′
C(1)-S(1)-Ce(1)
158.03(9)
76.46(9)
131.65(8)
84.35(7)
69.87(7)
129.06(7)
141.95(7)
89.29(5)
83.84(7)
132.81(6)
118.23(4)
109.33(7)
78.55(6)
78.40(5)
119.33(12)
O(3)-Ce(1)-O(2)
O(3)-Ce(1)-F(10)
O(2)-Ce(1)-F(10)
O(1)-Ce(1)-S(3)
F(10)-Ce(1)-S(3)
O(1)-Ce(1)-S(2)
F(10)-Ce(1)-S(2)
O(3)-Ce(1)-S(1)
O(2)-Ce(1)-S(1)
S(3)-Ce(1)-S(1)
O(3)-Ce(1)-S(1)′
O(2)-Ce(1)-S(1)′
S(3)-Ce(1)-S(1)′
S(1)-Ce(1)-S(1)′
81.62(9)
65.09(8)
134.30(8)
86.70(7)
76.23(6)
70.70(7)
64.31(6)
92.28(7)
75.66(7)
145.50(3)
86.46(7)
131.76(7)
154.74(3)
58.25(5)
Figure 3. ORTEP diagram of (py)4Sm(SC6F5)3 (4). Thermal ellipsoids
are drawn at the 50% probability level.
Table 3. Bond Lengths (Å) and Angles (deg) for (THF)3Ho(SC6F5)3
Ho(1)-O(1)
Ho(1)-F(1)
Ho(1)-S(1)
Ho(1)-O(3)
2.341(2)
2.579(2)
2.7241(14)
2.375(2)
Ho(1)-S(3)
Ho(1)-O(2)
Ho(1)-S(2)
2.7111(14)
2.375(2)
2.7169(14)
O(1)-Ho(1)-O(3)
O(3)-Ho(1)-O(2)
O(3)-Ho(1)-F(1)
O(1)-Ho(1)-S(3)
O(2)-Ho(1)-S(3)
O(1)-Ho(1)-S(2)
O(2)-Ho(1)-S(2)
S(3)-Ho(1)-S(2)
O(3)-Ho(1)-S(1)
F(1)-Ho(1)-S(1)
S(2)-Ho(1)-S(1)
153.45(8)
76.45(8)
64.58(7)
88.38(7)
83.54(7)
86.97(7)
80.42(7)
163.92(3)
129.94(6)
67.74(5)
95.42(5)
O(1)-Ho(1)-O(2)
O(1)-Ho(1)-F(1)
O(2)-Ho(1)-F(1)
O(3)-Ho(1)-S(3)
F(1)-Ho(1)-S(3)
O(3)-Ho(1)-S(2)
F(1)-Ho(1)-S(2)
O(1)-Ho(1)-S(1)
O(2)-Ho(1)-S(1)
S(3)-Ho(1)-S(1)
C(1)-S(1)-Ho(1)
77.00(8)
140.85(7)
138.31(7)
89.14(6)
81.71(6)
88.16(6)
111.24(6)
76.53(7)
153.39(6)
98.45(4)
106.14(11)
Figure 4. ORTEP diagram of (py)4Yb(SC6F5)3 (5). Thermal ellipsoids
are drawn at the 50% probability level.
Table 4. Bond Lengths (Å) and Angles (deg) for (py)4Sm(SC6F5)3
Sm(1)-N(2)
Sm(1)-N(4)
Sm(1)-S(1)
Sm(1)-N(3)
2.561(7)
2.619(7)
2.831(3)
2.581(7)
Sm(1)-F(1)
Sm(1)-S(2)
Sm(1)-N(1)
Sm(1)-S(3)
2.703(5)
2.867(3)
2.615(7)
2.809(3)
N(2)-Sm(1)-N(3)
N(3)-Sm(1)-N(1)
N(3)-Sm(1)-N(4)
N(2)-Sm(1)-F(1)
N(1)-Sm(1)-F(1)
N(2)-Sm(1)-S(3)
N(1)-Sm(1)-S(3)
F(1)-Sm(1)-S(3)
N(3)-Sm(1)-S(1)
N(4)-Sm(1)-S(1)
S(3)-Sm(1)-S(1)
N(3)-Sm(1)-S(2)
N(4)-Sm(1)-S(2)
S(3)-Sm(1)-S(2)
C(1)-S(1)-Sm(1)
109.6(3)
83.6(2)
142.1(2)
134.7(2)
66.0(2)
92.08(19)
86.00(17)
76.29(12)
75.98(17)
137.94(16)
86.19(8)
65.89(18)
78.71(17)
146.95(7)
106.4(3)
N(2)-Sm(1)-N(1)
N(2)-Sm(1)-N(4)
N(1)-Sm(1)-N(4)
N(3)-Sm(1)-F(1)
N(4)-Sm(1)-F(1
N(3)-Sm(1)-S(3)
N(4)-Sm(1)-S(3)
N(2)-Sm(1)-S(1)
N(1)-Sm(1)-S(1)
F(1)-Sm(1)-S(1)
N(2)-Sm(1)-S(2)
N(1)-Sm(1)-S(2)
F(1)-Sm(1)-S(2)
S(1)-Sm(1)-S(2)
158.1(2)
78.1(2)
80.9(2)
68.4(2)
132.8(2)
144.42(18)
68.38(17)
69.71(18)
131.79(17)
65.96(12)
83.78(18)
85.97(18)
128.26(12)
122.21(8)
Figure 5. ORTEP diagram of (DME)2Er(SC6F5)3 (6). Thermal ellipsoids
are drawn at the 50% probability level.
significant bond distances and angles are given in Table 3.
The equatorial thiolate ligand coordinates through both S(1)
and F(1) donor interactions, with a Ho-F(1) distance of
2.579(2) Å, as in Figure 2.
Pyridine complexes of Ln(C6F5)3 have similar structural
features. In both (py)4Sm(SC6F5)3 (4) and (py)4Yb(SC6F5)3
(5), the presence of the stronger neutral pyridine donor results
in the formation of monometallic compounds with only
terminal thiolate ligands. ORTEP diagrams for 4 and 5 are
given in Figures 3 and 4 respectively, and significant bond
geometries are given in Tables 4 and 5, respectively. In the
structure of eight-coordinate 4 (4N, 3S, 1F) there is a single
Sm-F dative interaction with a 2.703(5) Å Sm-F(1)
separation (Figure 3), and there are clear π-π interactions11
of pyridine (N4)/thiolate (S2), and between two thiolate
ligands (S(1) and S(3)). In the pyridine complex of the
smaller Yb(III) ion the coordination number has been reduced
to seven (4 nitrogen, 3 sulfur) to produce a pentagonal
bipyramidal geometry with two axial pyridine ligands, three
(11) Coates, G. W.; Dunn, A. R.; Henling, L. M.; Dougherty, D. A.; Grubbs,
R. H. Angew. Chem., Int. Ed. Engl. 1997, 36, 248.
Inorganic Chemistry, Vol. 41, No. 1, 2002 31

Melman et al.
Table 5. Bond Lengths (Å) and Angles (deg) for (py)4Yb(SC6F5)3
of divalent [(THF)2Eu(SC6F5)2]n and trivalent [(THF)2Sm-
(SC6F5)3]2, and clearly demonstrates how the chemical and
physical properties of compounds with fluorinated thiolate
ligands differ from those of their SC6H5 counterparts. A most
dramatic effect is the tendency of fluorinated thiolate ligands
to form complexes with reduced nuclearity. While ben-
zenethiolate compounds of the early lanthanides form
polymeric structures with metals as small as Sm(III),12 the
corresponding fluorinated derivatives are either dimeric
products or molecular species with Ln-F interactions serving
to complete the lanthanide coordination sphere. Reduced
nuclearity is a direct consequence of the fluorine substitution,
which reduces S basicity by polarizing electron density away
from S and into the arene functional group. The best example
of this effect comes from the Sm structures, where coordina-
tion complexes of LxSm(SC6F5)3 have consistently lower
nuclearity (dimer, L ) THF;3 monomer, L ) pyridine) than
their LxSm(SPh)3 counterparts12 (polymer, L ) THF; tet-
ramer, L ) pyridine). In both cases, the more basic pyridine
ligand is better able to disrupt Ln-S(R)-Ln bridging
interactions.
Yb(1)-N(3)
Yb(1)-N(1)
Yb(1)-S(3)
Yb(1)-N(4)
2.424(3)
2.466(3)
2.763(2)
2.437(3)
Yb(1)-S(2)
Yb(1)-N(2)
Yb(1)-S(1)
2.752(1)
2.457(3)
2.760(2)
N(3)-Yb(1)-N(4)
N(4)-Yb(1)-N(2)
N(4)-Yb(1)-N(1)
N(3)-Yb(1)-S(2)
N(2)-Yb(1)-S(2)
N(3)-Yb(1)-S(1)
N(2)-Yb(1)-S(1)
S(2)-Yb(1)-S(1)
N(4)-Yb(1)-S(3)
N(1)-Yb(1)-S(3)
S(1)-Yb(1)-S(3)
89.16(9)
176.11(9)
88.73(10)
76.30(7)
89.87(7)
141.57(7)
89.27(8)
65.47(4)
92.19(8)
65.43(7)
142.17(4)
N(3)-Yb(1)-N(2)
N(3)-Yb(1)-N(1)
N(2)-Yb(1)-N(1)
N(4)-Yb(1)-S(2)
N(1)-Yb(1)-S(2)
N(4)-Yb(1)-S(1)
N(1)-Yb(1)-S(1)
N(3)-Yb(1)-S(3)
N(2)-Yb(1)-S(3)
S(2)-Yb(1)-S(3)
C(1)-S(1)-Yb(1)
94.58(10)
141.42(9)
89.02(10)
89.95(7)
142.21(7)
87.11(8)
76.74(7)
76.17(7)
89.77(8)
152.35(3)
115.85(11)
Table 6. Bond Lengths (Å) and Angles (deg) for (DME)2Er(SC6F5)3
Er(1)-O(2)
Er(1)-O(3)
Er(1)-S(3B)
Er(1)-O(1)
2.384(2)
2.467(2)
2.700(8)
2.409(2)
Er(1)-S(3A)
Er(1)-S(2)
Er(1)-O(4)
Er(1)-S(1)
2.6942(16)
2.7215(10)
2.452(2)
2.7004(9)
O(2)-Er(1)-O(1)
O(1)-Er(1)-O(4)
O(1)-Er(1)-O(3)
66.25(9)
121.18(8)
151.99(8)
O(2)-Er(1)-O(4)
O(2)-Er(1)-O(3)
O(4)-Er(1)-O(3)
O(1)-Er(1)-S(3A)
O(3)-Er(1)-S(3A)
O(1)-Er(1)-S(1)
O(3)-Er(1)-S(1)
O(2)-Er(1)-S(3B)
70.66(8)
134.49(8)
65.90(8)
83.47(7)
70.81(7)
84.36(7)
83.78(6)
101.84(19)
72.64(18)
12.69(17)
86.68(7)
82.06(6)
145.24(4)
148.51(15)
O(2)-Er(1)-S(3A) 114.40(8)
Because Ln-F interactions are weak and thus readily
distorted, it is difficult to establish exactly what constitutes
a Ln-fluoride dative interaction. Assessments based on
comparisons between interatomic distances and van der
Waals radii are impossible because there are no values
available for the lanthanide ions. Still, relatively short Ln-F
separations can be interpreted by comparison with published
values for the van der Waals radii13 of F (1.47 Å) and O
(1.52 Å) or N (1.55 Å), and the abundance of dative Ln-
O(THF) or Ln-N (pyridine) bonds in the structures reported
here. In the majority of cases, the Ln-F is ca. 0.1-0.2 Å
longer than the average bonds to either THF or pyridine: in
1 (Ce-O ) 2.53 Å, Ce-F ) 2.75 Å), 2 (Ho-O ) 2.36 Å,
Ho-F ) 2.58 Å), or 4 (Sm-N ) 2.59 Å, Sm-F ) 2.70
Å). As such, these are clearly Ln-F interactions. Less well
defined is the Ln-F interaction in 6, where the average
Er-O bond is 2.43(2) Å but the Er-F(6) distance is
2.945(5) Å. In this case, a significant Er-F interaction can
be discounted by comparison of Er-S bonds in 6 relative to
the Ho-S bonds in 2; the Ho-S bond lengths average 0.01
Å longer than the Er-S bond lengths. This difference is
precisely that expected from ionic radius summation argu-
ments, and therefore both Ln effectively have the same
coordination number (7): Ho (3S, 3O, 1F); Er (3S, 4O).
O(4)-Er(1)-S(3A)
O(2)-Er(1)-S(1)
O(4)-Er(1)-S(1)
S(3A)-Er(1)-S(1)
O(1)-Er(1)-S(3B)
O(3)-Er(1)-S(3B)
S(1)-Er(1)-S(3B)
O(1)-Er(1)-S(2)
O(3)-Er(1)-S(2)
S(1)-Er(1)-S(2)
C(1)-S(1)-Er(1)
79.80(7)
139.38(6)
149.54(6)
87.80(5)
79.07(16) O(4)-Er(1)-S(3B)
77.90(17) S(3A)-Er(1)-S(3B)
99.14(18) O(2)-Er(1)-S(2)
131.23(6)
74.77(6)
O(4)-Er(1)-S(2)
S(3A)-Er(1)-S(2)
S(3B)-Er(1)-S(2)
93.19(3)
107.44(11)
terminal equatorial thiolates, and no Ln-F bonds (Figure
4). In the Yb structure 5 there are significant π-π stacking
interactions between the S(2) and S(3) thiolates and a
sandwiched pyridine (N1), as well as π-π interactions
between the S(2) thiolate and a pyridine (N3) ligand. The
compound has an intense visible absorption band with a
maximum at 440 nm that can be assigned as a S to Yb charge
transfer absorption on the basis of earlier resonance Raman
measurements.12
Because of the solubilizing tendency of these fluorinated
ligands, transmetalation reactions of Ln with Hg(SC6F5)2 will
run to completion in solvents as apolar as DME. Transmeta-
lation of Hg(SC6F5)2 with Er in DME gives the first
structurally characterized Er thiolate (DME)2Er(SC6F5)3 (6).
An ORTEP diagram of this compound is given in Figure 5,
and significant bond geometries are given in Table 6. There
is only one thiolate (S2) that could possibly be viewed as
coordinating through both S and F atoms, with a compara-
tively long 2.948(6) Å Er-F(6) separation. In this compound
the one thiolate (S2) with the closest Er-F interaction is
positioned to interact strongly with the neighboring π system
on the ring attached to S1. This compound decomposes
thermally to form ErF3, (SC6F5)2, and (SC6F4)x (x ) 2, 3).
Substitution of SPh by SC6F5 appears to influence the
length of the Ln-S bond. Comparisons are difficult, because
structurally characterized tris-benzenethiolate compounds of
the lanthanide elements represent a small family of com-
pounds (including [(THF)Sm(SPh)3]n,12 [(py)2Sm(SPh)3]4,12
(hmpa)3Ln(SPh)3 (Ln ) Sm, Yb),14 [(py)3Tm(SPh)3]2,12 and
(py)3Yb(SPh)315) and because both coordination number and
ancillary ligands have a significant impact on Ln-S bond
(12) Lee, J.; Freedman, D.; Melman, J.; Brewer, M.; Sun, L.; Emge, T. J.;
Long, F. H.; Brennan, J. G. Inorg. Chem. 1998, 37, 2512.
(13) Shannon, R. D. Acta Crystallogr. A 1976, 32, 751.
(14) Mashima, K.; Nakayama, Y.; Shibahara, T.; Fukumoto, H.; Nakamura,
A. Inorg. Chem. 1996, 35, 93.
Discussion
This diverse array of Ln(SC6F5)3 coordination complexes
complements the initially reported3 syntheses and structures
32 Inorganic Chemistry, Vol. 41, No. 1, 2002

TriWalent Ln Compounds with Fluorinated Thiolate Ligands
lengths. Most uncomplicated is the comparison between the
[(py)3Tm(SPh)3]2 and (py)4Yb(SC6F5)3, given that both
compounds are seven-coordinate structures with neutral
pyridine donor ligands and no Ln-F interactions, and the
effect of Ln substitution is a uniform reduction of all bonds
(0.01 Å) for the smaller Yb(III) ion (0.02 Å, if we use the
difference in average Tm-N and Yb-N distances to
approximate the effective change in Ln radii). Terminal
Ln-S bond lengths of 2.706(5) Å in the Tm compound and
2.765(2) Å in the Yb compound indicate that fluorination
effectively increases the Ln-S bond length by about 0.05
Å.
While there are significant differences between the shortest
and longest Ln-S bonds in the structures of molecular 2, 3,
4, and 6, there is no clear trend that would indicate that bond
lengths are directly related to geometry, as has been noted
in the structures of octahedral tris-thiolate compounds in the
literature.15,16 In 2, the three thiolate ligands are arranged
such that S2 and S3 are maximally apart (S2-Ho-S3,
163.92°; S1-Ho-S2, 111.24(6)°; S1-Ho-S3, 98.54(4)°),
and the longest Ho-S bond is to S1. The Ho-S bond lengths
are essentially equal, with the difference between the shortest
and longest Ho-S bond being only 0.013 Å. Such structural
features are entirely compatible with ionic bonding models,
which would predict that all Ln-S bonds should be equal,
and that any bond length inequivalence would have origins
in the unequal ligand-ligand repulsive interactions (i.e., in
1, where S1 is close to the other two thiolates, and thus
should be slightly distanced because of the additional anion-
anion repulsions).
A similar arrangement of thiolates is found in the Er-
DME complex 6, where two thiolates are further apart (S2-
Er-S3a, 145.31(3)°; S1-Er-S2, 93.19(3)°; S1-Er-S3a,
97.99(5)°). There is a slightly greater range of Er-S bond
lengths relative to 3 (by inference, given isostructural 2),
with the difference between smallest and largest Er-S bond
being 0.029 Å. In this compound, however, the longest bond
(Er-S2) is not found at the ligand site with the greatest
anion-anion repulsions (S1).
Eight-coordinate 4 has a slightly different arrangement of
anionic ligands, with S2 considerably apart from S1 and S3
(S1-Sm-S3, 86.16(8)°; S1-Sm-S2, 122.21(8)°; S2-Sm-
S3 146.95(7)°). There is also a more dramatic spread of
Sm-S bond lengths (0.058 Å) in the molecule, with the
longest bond going to the anion with the least ligand-ligand
repulsions. Finally, the anion arrangement in seven-
coordinate 5 is similar to that in 4, although with no Yb-F
interaction 5 adopts a nearly ideal pentagonal bipyramidal
geometry with axial pyridine ligands and three equatorial
thiolates. Both pyridine compounds 4 and 5 have a similar
range of metal-sulfur bond lengths (Yb, 0.054 Å; Sm, 0.058
Å). Even so, in contrast to 4, the bond to the relatively
isolated S1 (S1-Yb-S2, 141.42(4)°; S1-Yb-S3, 153.45-
(4)°; S2-Yb-S3, 65.12(4)°) is one of two essentially equal
Yb-S bonds in the molecule (Yb-S1, 2.778(1) Å; Yb-S2,
2.781(1) Å; Yb-S3, 2.727(1) Å), while the chemically
equivalent Yb-S bonds (if one ignores π stacking inter-
actions) represent the shortest and longest Yb-S bond
lengths in the structure. Clearly, directional bonding is absent
in these compounds, and factors other than Ln-S covalent
bonding have the most significant impact on the length of
the Ln-S bond.
Isolation of the Yb(III) compound 5 allows for an
examination of the effect fluoro substitution has on the
energy of S to Ln(III) charge transfer processes. Absorption
maxima for both Yb(SPh)3 (λmax ) 470 nm)15 and Yb(2-S-
NC5H4)3 (λmax ) 388 nm)17 in pyridine have been recorded,
and the absorption maximum of the fluorinated derivative 5
(λmax ) 440 nm) reveals that SC6F5 shifts the LMCT
excitation to higher energy relative to SPh, but this excitation
is lower in energy than the absorption of the corresponding
pyridinethiolate compound. Relatively stable Ln(III) ground
states of the fluorinated and pyridinethiolate molecules have
a dramatic impact on chemical reactivity. For example,
elemental S reacts with Ln(SPh)3 to form sulfido clusters18
with the reductive elimination of PhSSPh, but there does
not appear to be any reaction between S and either Yb(2-
S-NC5H4)3 or Yb(SC6F5)3. In order to prepare chalcogenido
clusters with fluorinated thiolate ligands, heteroanion syn-
thetic methods19 must be developed further.
Conclusion
The Ln-F dative interaction in Ln(SC6F5)3 compounds
is surprisingly prevalent and can persist in the presence of
donor ligands as basic as pyridine. While there is a clear
tendency for F to coordinate to Ln as the size of the Ln radius
increases, an absolute correlation between ionic size and the
number of Ln-F bonds does not exist because these bonds
are particularly susceptible to external influences such as
crystal packing effects. Structure, solubility, and electronic
properties are all clearly impacted by the electron-withdraw-
ing nature of the fluoride ligands. Chemically, the fluoride
substituents render these compounds unreactive toward
elemental chalcogen.
Acknowledgment. This work was supported by the
National Science Foundation under Grant CHE 9982625.
Supporting Information Available: X-ray crystallographic files
in CIF format for the crystal structures of 1, 2, 4, 5, and 6.
This material is available free of charge via the Internet at
http://pubs.acs.org.
IC0104813
(17) Berardini, M.; Lee, J.; Freedman, D.; Lee, J.; Emge, T. J.; Brennan,
J. G. Inorg. Chem. 1997, 36, 5772.
(18) (a) Freedman, D.; Emge, T. J.; Brennan, J. G. J. Am. Chem. Soc. 1997,
119, 11112. (b) Melman, J. H.; Emge, T. J.; Brennan, J. G. Inorg.
Chem. 1999, 38, 2117. (c) Melman, J. H.; Emge, T. J.; Brennan, J. G.
Chem. Commun. 1997, 2269.
(15) Lee, J.; Brewer, M.; Berardini, M.; Brennan, J. Inorg. Chem. 1995,
34, 3215.
(16) (a) Freedman, D.; Melman, J.; Emge, T. J.; Brennan, J. G. Inorg. Chem.
1998, 37, 4162. (b) Aspinall, H.; Cunningham, S. A.; Maestro, P.;
Macaudiere, P. Inorg. Chem. 1998, 37, 5396.
(19) (a) Melman, J. H.; Fitzgerald, M.; Freedman, D.; Emge, T. J.; Brennan,
J. G. J. Am. Chem. Soc. 1999, 121, 10247. (b) Kornienko, A.; Melman,
J.; Emge, T.; Brennan, J. Inorg. Chem., in press.
Inorganic Chemistry, Vol. 41, No. 1, 2002 33