Synthesis and structure of a distorted octahedral palladium(II) complex coordinated with a tetrathioether ligand tethered with bulky substituents

Article abstract of DOI:10.1021/ic050944v

A new type of an o-phenylene-bridged tetrathioether ligand tethered with extremely bulky substituents, 2,4,6-tris-[bis(trimethylsilyl)methyl]phenyl (Tbt) groups, at its terminal sulfur atoms, TbtS[(o-phenylene)S]₃Tbt (1), was synthesized by taking advantage of the coupling reaction of thiols with iodobenzenes using Cu₂O in 2,4,6-trimethylpyridine. Complexation of 1 with Na₂PdCl₄ gave the corresponding dichloropalladium(II) complex, [PdCl₂(1)] (7). The X-ray structural analysis of 7 indicated that the central palladium metal is in a distorted octahedral environment, where the two inner sulfur atoms of 1 and the two chlorine atoms form a square planar arrangement around the palladium metal and the two terminal sulfur atoms of 1 weakly coordinate to the palladium center at the axial positions. In addition, a phenyl analogue of 1, PhS[(o-phenylene)S] ₃Ph (2), was synthesized by a method similar to that for 1. Reaction of 2 with Na₂PdCl₄ gave the corresponding dichloropalladium(II) complex, [PdCl₂(2)] (8). X-ray crystallography of 8 showed a type of the structure different from the distorted octahedral structure in 7, i.e., a square planar arrangement around the central palladium atom with the one terminal sulfur atom of 2, its neighboring sulfur atom, and the two chlorine atoms. The results of the NMR studies on 8 in a CDCl ₃ solution were not consistent with the results of the X-ray crystallography and suggested the coordination of the two inner sulfur atoms of 2 to the palladium metal, although a possibility of the existence of the rapid interconversion among isomers could not be excluded.

Full text of DOI:10.1021/ic050944v

Inorg. Chem. 2005, 44, 8561−8568
Synthesis and Structure of a Distorted Octahedral Palladium(II) Complex
Coordinated with a Tetrathioether Ligand Tethered with Bulky
Substituents
Nobuhiro Takeda, Daisuke Shimizu, and Norihiro Tokitoh*
Institute for Chemical Research, Kyoto UniVersity, Gokasho, Uji, Kyoto 611-0011, Japan
Received June 11, 2005
A new type of an o-phenylene-bridged tetrathioether ligand tethered with extremely bulky substituents, 2,4,6-tris-
[bis(trimethylsilyl)methyl]phenyl (Tbt) groups, at its terminal sulfur atoms, TbtS[(o-phenylene)S]3Tbt (1), was synthesized
by taking advantage of the coupling reaction of thiols with iodobenzenes using Cu2O in 2,4,6-trimethylpyridine.
Complexation of 1 with Na2PdCl4 gave the corresponding dichloropalladium(II) complex, [PdCl2(1)] (7). The X-ray
structural analysis of 7 indicated that the central palladium metal is in a distorted octahedral environment, where
the two inner sulfur atoms of 1 and the two chlorine atoms form a square planar arrangement around the palladium
metal and the two terminal sulfur atoms of 1 weakly coordinate to the palladium center at the axial positions. In
addition, a phenyl analogue of 1, PhS[(o-phenylene)S]3Ph (2), was synthesized by a method similar to that for 1.
Reaction of 2 with Na2PdCl4 gave the corresponding dichloropalladium(II) complex, [PdCl2(2)] (8). X-ray crystallography
of 8 showed a type of the structure different from the distorted octahedral structure in 7, i.e., a square planar
arrangement around the central palladium atom with the one terminal sulfur atom of 2, its neighboring sulfur atom,
and the two chlorine atoms. The results of the NMR studies on 8 in a CDCl3 solution were not consistent with the
results of the X-ray crystallography and suggested the coordination of the two inner sulfur atoms of 2 to the
palladium metal, although a possibility of the existence of the rapid interconversion among isomers could not be
excluded.
Introduction
around the palladium(II) atom and the remaining one or two
sulfur atoms weakly coordinate to the palladium(II) atom
[Pd‚‚‚S: 2.96-3.27 Å] at the axial positions. In addition,
the 9S3 ligand has been known to stabilize mononuclear
palladium(III) species,4 which are generally known to be
unstable. These unique properties of cyclic polythioether
ligands are considered to be caused by their moderate,
geometric preference of facial coordination and their ability
to adjust the coordination modes and conformations to the
geometric preference of the oxidation states of the metals.5
Acyclic polythioethers can more easily change their coor-
Palladium(II) complexes generally have square planar
geometry around the palladium atom, and six-coordinate
complexes of palladium(II) are very rare. Cyclic poly-
thioether (crown thioether) ligands such as 1,4,7-trithia-
cyclononane (9S3),1 1,4,7,10,13,16-hexathiacyclooctadecane
(18S6),2 and 1,4,7-trithiacyclodecane (10S3)3 reportedly
complexed with palladium(II) metals to give the correspond-
ing five- or six-coordinate palladium(II) complexes, in which
the four sulfur atoms are arranged in a square planar fashion
* To whom correspondence should be addressed. E-mail: tokitoh@
boc.kuicr.kyoto-u.ac.jp.
(1) (a) Wieghardt, K.; Ku¨ppers, H.-J.; Raabe, E.; Kru¨ger, C. Angew. Chem.,
Int. Ed. Engl. 1986, 25, 1101-1103. (b) Blake, A. J.; Holder, A. J.;
Hyde, T. I.; Roberts, Y. V.; Lavery, A. J.; Schro¨der, M. J. Organomet.
Chem. 1987, 323, 261-270.
(2) Blake, A. J.; Gould, R. O.; Lavery, A. J.; Schro¨der, M. Angew. Chem.,
Int. Ed. Engl. 1986, 25, 274-276.
(3) (a) Grant, G. J.; Sanders, K. A.; Setzer, W. N.; VanDerveer, D. G.
Inorg. Chem. 1991, 30, 4053-4056. (b) Chandrasekhar, S.; McAuley,
A. Inorg. Chem. 1992, 31, 2663-2665.
(4) Blake, A. J.; Holder, A. J.; Hyde, T. I.; Schro¨der, M. J. Chem. Soc.,
Chem. Commun. 1987, 987-988.
(5) For reviews on crown thioethers, see: (a) Cooper, S. R. Acc. Chem.
Res. 1988, 21, 141-146. (b) Blake, A. J.; Schro¨der, M. AdV. Inorg.
Chem. 1990, 35, 1-80. (c) Cooper, S. R.; Rawle, S. C. Struct. Bonding
(Berlin) 1990, 72, 1-72. (d) Kellogg, R. M. In Crown Compounds:
Toward Future Applications, Cooper, S. R., Ed.; Wiley VCH: New
York, 1992. (e) Levason, W.; Reid, G. In ComprehensiVe Coordination
Chemistry II, from Biology to Nanotechnology; Lever, A. B. P., Ed.;
Elsevier Ltd.: Oxford, U.K., 2004; Vol. 1, pp 399-410.
10.1021/ic050944v CCC: $30.25
Published on Web 10/01/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 23, 2005 8561

Takeda et al.
Chart 1
Scheme 1. Synthesis of Tetrathioether Ligands 1 and 2
dination modes and conformations; however, the coordination
chemistry of acyclic polythioether ligands has been less
investigated probably due to their relatively low coordination
ability to metals.5b,c,6
On the other hand, we have succeeded in the syntheses of
a variety of highly reactive low-coordinate species containing
main group metals by taking advantage of effective steric
protection groups, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl
(Tbt) and 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethyl-
silyl)methyl]phenyl (Bbt) groups.7 In addition, we have
recently succeeded in the application of the Tbt and Bbt
groups to the stabilization of transition metal complexes, i.e.,
the synthesis of the first platinum-disulfido and -diselenido
complexes by the use of extremely bulky aryldimethylphos-
phines bearing the Tbt or Bbt group.8
52% yield. Further coupling reaction of 5 with 0.5 equiv of
1,2-benzenedithiol under conditions similar to the above
coupling reaction using Cu2O gave the expected tetrathioether
1 in a good yield.
To study the effects of bulky substituents, we examined
the synthesis of a ligand bearing phenyl groups instead of
Tbt groups. The phenyl-substituted ligand 2 was synthesized
by the method similar to that for 1, though in a relatively
low yield (Scheme 1).
In this paper, we report the synthesis of a new bulky tetra-
thioether ligand 1 (Chart 1) tethered with two Tbt substituents
and its application to the synthesis of a palladium(II)
complex.9 It is expected that the introduction of bulky
substituents to an acyclic tetrathioether ligand leads to the
moderate restriction of the conformation of the ligand and
the kinetic stabilization of the metal center. To investigate
the effect of the bulky substituents, synthesis of the phenyl
analogue of 1 (2) and its complexation with a palladium
metal are also described.
Structure of Tetrathioether Ligands 1 and 2. Tetrathio-
ether ligands 1 and 2 were characterized by the NMR spectra,
MS, and elemental analysis, and their molecular structures
in the crystalline states were definitively determined by X-ray
structural analyses. Figures 1 and 2 show the ORTEP
drawings of 1 and 2, respectively, and the selected bond
lengths, angles, and torsion angles are summarized in Table
1. While tetrathioether 2 has a conformation close to C2
symmetry, in the case of 1 the conformations around the S2
and S3 atoms are very different from each other. All the
C-S bond lengths of 1 and 2 [1.76-1.78 Å] are usual as
those of common diaryl sulfides [1.762-1.774 Å].11 It is
noteworthy that each of the C1-S1-C28 and C45-S4-
C46 planes in 1 is nearly perpendicular to the benzene ring
of its connecting Tbt group (C28-S1-C1-C6 ) 91.3(5)°
and C45-S4-C46-C47 ) 80.6(5)°) and is almost parallel
to its neighboring o-phenylene ring (C1-S1-C28-C33 )
178.0(4)° and C46-S4-C45-C40 ) 175.1(5)°). This
conformation in 1 can be explained in terms of the steric
hindrance caused by the Tbt groups.
Results and Discussion
Synthesis of Tetrathioether Ligands 1 and 2. The
synthesis of tetrathioether ligand 1 was examined by suc-
cessive coupling reactions of thiols with iodobenzenes. Tbt-
substituted thiol 3 was synthesized by the reaction of TbtLi,
prepared from TbtBr and tert-butyllithium, with elemental
sulfur, followed by the treatment of the resulting TbtSLi with
H2O (Scheme 1).
Coupling reaction of 3 with 1,2-diiodobenzene using Cu2O
in refluxing 2,4,6-trimethylpyridine10 afforded sulfide 5 in
(6) (a) Levason, W.; Reid, G. In ComprehensiVe Coordination Chemistry
II, from Biology to Nanotechnology; Lever, A. B. P., Ed.; Elsevier
Ltd.: Oxford, U.K., 2004; Vol. 1, pp 391-398. (b) Murray, S. G.;
Hartley, F. R. Chem. ReV. 1981, 81, 365-414.
(7) (a) Okazaki, R.; Tokitoh, N. Acc. Chem. Res. 2000, 33, 625-630. (b)
Tokitoh, N. Acc. Chem. Res. 2004, 37, 86-94. (c) Tokitoh, N. Bull.
Chem. Soc. Jpn. 2004, 77, 429-441.
(8) (a) Nagata, K.; Takeda, N.; Tokitoh, N. Angew. Chem., Int. Ed. 2002,
41, 136-138. (b) Nagata, K.; Takeda, N.; Tokitoh, N. Chem. Lett.
2003, 32, 170-171. (c) Nagata, K.; Takeda, N.; Tokitoh, N. Bull.
Chem. Soc. Jpn. 2003, 76, 1577-1587.
(9) A part of this paper had been preliminarily reported: Tokitoh, N.;
Shimizu, D.; Takeda, N.; Sasamori, T. Phosphorus, Sulfur, Silicon
2005, 180, 1241-1245.
(10) The synthesis of diaryl ethers by the reaction of phenols with aryl
halides using Cu2O catalyst in 2,4,6-trimethylpyridine has been
reported; see: Bacon, R. G. R.; Stewart, O. J. J. Chem. Soc. 1965,
4953-4961.
Figure 1. ORTEP drawing of 1 with thermal ellipsoids (50% probability).
Hydrogen atoms, trimethylsilyl groups, and a solvent molecule were omitted
for clarity.
8562 Inorganic Chemistry, Vol. 44, No. 23, 2005

A Distorted Octahedral Pd(II)-Tetrathioether Complex
Table 1. Selected Bond Lengths (Å), Angles (deg), and Torsion
Angles (deg)
1
2
S1-C1
1.769(6)
1.765(6)
1.766(6)
1.776(6)
1.772(6)
1.771(7)
1.771(7)
1.767(6)
S1-C6
1.7740(16)
1.7621(16)
1.7727(16)
1.7822(16)
1.7802(15)
1.7757(16)
1.7681(16)
1.7775(15)
S1-C28
S2-C33
S2-C34
S3-C39
S3-C40
S4-C45
S4-C46
S1-C7
S2-C12
S2-C13
S3-C18
S3-C19
S4-C24
S4-C25
C28-S1-C1
C33-S2-C34
C40-S3-C39
C46-S4-C45
101.8(3)
103.9(3)
101.1(3)
103.2(3)
C7-S1-C6
103.53(7)
102.48(7)
102.64(7)
104.63(7)
C12-S2-C13
C19-S3-C18
C24-S4-C25
C28-S1-C1-C6
C1-S1-C28-C33
91.3(5)
178.0(4)
C34-S2-C33-C28 66.5(5)
C1-C6-S1-C7
-123.94(13)
-157.99(13)
-77.49(14)
C6-S1-C7-C12
C7-C12-S2-C13
C33-S2-C34-C39 -156.1(5) C12-S2-C13-C18 164.94(12)
C40-S3-C39-C34 139.2(5)
C39-S3-C40-C45 113.6(5)
C13-C18-S3-C19 165.82(12)
C18-S3-C19-C24 -78.62(14)
Figure 2. ORTEP drawing of 2 with thermal ellipsoids (50% probability).
C46-S4-C45-C40 -175.1(5) C19-C24-S4-C25 167.38(12)
C45-S4-C46-C47 80.6(5)
C24-S4-C25-C30 132.39(12)
1
The H and 13C NMR spectra of 1 and 2 showed that
the two terminal TbtS(o-phenylene) (for 1) and PhS(o-
phenylene) (for 2) units were equivalent, respectively,
suggesting flexible structures of 1 and 2 in solution.
phosphine ligands.14 By contrast, to our knowledge, there
has been no report on the X-ray structural analysis of a
neutral, 6-coordinate palladium(II) complex except for
6-coordinate complexes having intermolecular or intra-
molecular Pd‚‚‚H interactions.15
Synthesis and Structure of Palladium(II) Complex 7
of Tetrathioether Ligand 1. When 1 was allowed to react
with Na2PdCl4 in ethanol at reflux for 5 min, the starting
red solution turned yellow with the formation of orange
precipitates. Further refluxing for 30 min resulted in the
almost quantitative formation of the corresponding dichloro-
palladium complex 7 as orange crystals, which are slightly
soluble in ethanol (eq 1). The structure of 7 was determined
by NMR spectrometry, ESI MS, elemental analysis, and
single-crystal X-ray diffraction.
The Pd1-Cl1 (2.3117(9) Å) bond distance is within the
range of those in the reported tetracoordinate palladium(II)
complexes (2.298-2.354 Å).16 The Pd1-S1 [2.2615(9) Å]
bond distance is close to those of some 4- or 5-coordinate
cis-dichloropalladium(II) complexes having macrocyclic
thioether ligands (2.246-2.269 Å)17 and is slightly shorter
than those of cationic palladium(II)-crown thioether com-
plexes (2.31-2.33 Å)1,2 except for [Pd(10S3)2](PF6)2
[2.2584(15) and 2.2789(14) Å].3a The distances between the
palladium and the two terminal sulfur atoms [Pd1‚‚‚S2 )
3.1755(8) Å] are shorter than the sum of the van der Waals
radii of palladium and sulfur atoms (3.43 Å).18 This suggests
weak interactions between the palladium (Pd1) and the
terminal sulfur atoms (S2 and S2*) in the crystalline state.
It is noteworthy that the torsion angles around the terminal
sulfur atoms in palladium complex 7 [C9-S2-C10-C11
) 94.5(3)°, C4-C9-S2-C10 ) 178.6(3)°] are almost
similar to those of the free ligand 1. This result suggests
that the extremely bulky Tbt groups put restrictions on the
conformation of ligand 1 in the structure of complex 7 as
The X-ray structural analysis of 7 showed the C2 sym-
metrical distorted octahedral structure, where the inner two
sulfur atoms of ligand 1 and the two chlorine atoms form a
square planar arrangement around the palladium(II) atom and
the two terminal sulfur atoms of 1 weakly coordinate to the
palladium center at the axial positions (Figure 3). A few
examples for cationic, 6-coordinate complexes of pal-
ladium(II) have been synthesized using crown thioether
ligands (e.g., 9S3,1 18S6,2 and 10S33), S- and N-donor
macrocyclic ligands [e.g., 1,4,10,13-tetrathia-7,16-diaza-
cyclooctadecane ([18]aneN2S4)12 and 1,4-dithia-7-azacyclo-
nonane ([9]aneNS2)13], and tris(2,4,6-trimethoxyphenyl)-
(14) Dunbar, K. R.; Sun, J.-S. J. Chem. Soc., Chem. Commun. 1994, 2387-
2388.
(15) (a) Bailey, N. A.; Mason, R. J. Chem. Soc. A 1968, 2594-2605. (b)
Debaerdemaeker, T.; Kutoglu, A.; Schmid, G.; Weber, L. Acta
Crystallogr., Sect. B 1973, 29, 1283-1288.
(16) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson, D.
G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1989, S1-S83.
(17) (a) Arca, M.; Blake, A. J.; Lippolis, V.; Montesu, D. R.; McMaster,
J.; Tei, L.; Schro¨der, M. Eur. J. Inorg. Chem. 2003, 1232-1241. (b)
Lucas, C. R.; Liang, W.; Miller, D. O.; Bridson, J. N. Inorg. Chem.
1997, 36, 4508-4513. (c) Lee, G.-H.; Tzeng, B.-C. Acta Crystallogr.
1996, C52, 879-882. (d) Blake, A. J.; Freeman, G.; Schro¨der, M.;
Yellowlees, L. J. Acta Crystallogr. 1993, C49, 167-168. (e) Blake,
A. J.; Holder, A. J.; Roberts, Y. V.; Schro¨der, M. Acta Crystallogr.
1988, C44, 360-361.
(11) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A.
G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1-S19.
(12) (a) Reid, G.; Blake, A. J.; Hyde, T. I.; Schro¨der, M. J. Chem. Soc.,
Chem. Commun. 1988, 1397-1399. (b) Blake, A. J.; Reid, G.;
Schro¨der, M. J. Chem. Soc., Dalton Trans. 1990, 3363-3373.
(13) Blake, A. J.; Crofts, R. D.; de Groot, B.; Schro¨der, M. J. Chem. Soc.,
Dalton Trans. 1993, 485-486.
(18) Bondi, A. J. Phys. Chem. 1964, 68, 441-451.
Inorganic Chemistry, Vol. 44, No. 23, 2005 8563

Takeda et al.
Figure 4. ORTEP drawing of 8 with thermal ellipsoids (50% probability).
Selected bond distances (Å) and angles (deg): Pd1-S1 ) 2.2448(7), Pd1-
S2 ) 2.2642(8), Pd1-Cl1 ) 2.3115(8), Pd1-Cl2 ) 2.3077(8), Pd1‚‚‚S3
) 3.4305(8); S1-Pd1-S2 ) 90.22(3), S1-Pd1-Cl1 ) 87.92(3), S2-
Pd1-Cl2 ) 88.76(3), Cl1-Pd1-Cl2 ) 93.35(3).
reflectance decrease in the region similar to the absorption
region of 7 in hexane. This region is similar to the absorption
region of square planar cis-dichloropalladium(II) complexes
with dithioether ligands (λmax ) 380-450 nm).19 If the trend
of the UV/vis spectra for the cationic 6-coordinate complexes
of palladium(II) with these macrocyclic ligands can be
applied to the neutral dichloropalladium(II) complex 7, this
result may suggest relatively weak or no interaction between
the palladium and the terminal sulfur atoms both in the solid
state and in solution.
Synthesis and Structure of Palladium(II) Complex 8
of Tetrathioether Ligand 2. To investigate the effects of
bulky substituents, we examined the synthesis of a dichloro-
palladium complex coordinated with tetrathioether ligand 2.
When a mixture of 2 and Na2PdCl4 was refluxed in ethanol
for 1 h, the corresponding dichloropalladium complex 8 was
obtained as orange crystals (eq 2). The X-ray structural
analysis of 8 showed that the palladium metal is coordinated
by the one terminal and the one inner sulfur atoms of ligand
2 (Figure 4) in contrast to the distorted octahedral coordina-
tion structure of Tbt-analogue 7. Complex 8 has a square
planar structure with normal Pd-Cl bond lengths. The Pd1-
S1 and Pd1-S2 bond lengths are similar to the Pd1-S1 bond
lengths of 7, and the Pd1-S3 distance [3.4305(8) Å] is close
to the sum of the van der Waals radii of palladium and sulfur
atoms (3.43 Å).18 This result suggests that there is little
interaction between Pd1 and S3 atoms in complex 8.
Figure 3. ORTEP drawing of 7 with thermal ellipsoids (50% probability).
Hydrogen atoms and solvent molecules were omitted for clarity. Selected
bond distances (Å), angles (deg), and torsion angles (deg): Pd1-S1 )
2.2615(9), Pd1-Cl1 ) 2.3117(9), Pd1‚‚‚S2 ) 3.1755(8); S1-Pd1-S1* )
89.45(5), S1-Pd1-Cl1 ) 88.15(3), Cl1-Pd1-Cl1* ) 95.37(5), S1-Pd1-
S2 ) 71.19(3), S1*-Pd1-S2 ) 82.08(3), Cl1-Pd1-S2 ) 89.37(3), Cl1*-
Pd1-S2 ) 116.55(3); C4-C9-S2-C10 ) 178.6(3), C9-S2-C10-C11
) 94.5(3).
well as in that of 1; that is, the ligand 1 preferably has the
conformation in which the C-S(terminal)-C planes
are almost perpendicular to the benzene rings of the Tbt
groups and almost parallel to the neighboring o-phenylene
rings.
As for the cationic 6-coordinate complexes of palladium(II)
with crown thioether ligands or S- and N-donor macrocyclic
ligands, it has been known that complexes with relatively
strong interactions with the sulfur atom at the axial posi-
tions have a blue or green color, while complexes with
relatively weak or no interactions have a yellow or brown
color. For example, [Pd(9S3)2][PF6]2 [ax Pd-S 2.952(4) Å],1
[Pd(10S3)2][BPh4]2 [ax Pd-S 3.11 Å],3a [Pd(10S3)2][PF6]2
[ax Pd-S 3.034(1) Å],3b and [Pd([18]aneN2S4)][BPh4]2 [ax
Pd-S 2.954(4) and 3.000(3) Å]12 have an absorption
maximum in the visible region at 615 (blue), 602 (blue-
green), 598 (green), and 514 nm (green) respectively, while
[Pd(18S6)](PF6)2 [ax Pd-S 3.2730(17) Å] has yellow-brown
color.2 These absorptions around 500-600 nm have been
assigned to d-d transitions by the small values of the
extinction coefficient. Complex 7, the X-ray crystallographic
analysis of which suggests the weak interactions between
the palladium (Pd1) and the terminal sulfur atoms (S2 and
S2*) in the crystalline state, has an orange color with
absorption maxima at 398 (ꢀ 6.5 × 103), 305 (sh, 7.6 × 103),
and 294 (sh, 5.3 × 103) nm in hexane. The diffuse UV/vis
reflectance spectrum of 7 in the solid state showed the
To clarify the reason for the preference of the 8b-type
structure over the 8a-type structure in the crystalline state
(Chart 2), the energies of these two linkage isomers, 8a,b,
were calculated with B3LYP/LANL2DZ(ECP) for the Pd
and 6-31G(d) for C, S, Cl, and H (Figure 6).20 Contrary to
(19) (a) Hartley, F. R.; Murray, S. G.; Levason, W.; Soutter, F. E.;
McAuliffe, C. A. Inorg. Chim. Acta 1979, 35, 265-277. (b) Takeda,
N.; Shimizu, D.; Sasamori, T.; Tokitoh, N. Acta Crystallogr., Sect. E
2005, 61, m1408-m1410.
(20) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652. (b) Becke, A.
D. Phys. ReV. 1988, A38, 3098-3100. (c) Lee, C.; Yang, W.; Parr,
R. G. Phys. ReV. 1988, B37, 785-789.
8564 Inorganic Chemistry, Vol. 44, No. 23, 2005

A Distorted Octahedral Pd(II)-Tetrathioether Complex
Table 2. Redox Potentials (V vs Fc/Fc+) of 7-9
Chart 2
compd
type
Epa
Epc
E1/2
7
oxidna
oxidnb
rednb
-0.24
-0.04
-0.33
-0.13
-1.84
-0.29
-0.09
8
9
oxidna
rednb
+0.97
-1.18
-0.26
-0.10
-1.28
oxidna
oxidnb
rednb
-0.17
-0.02
-0.22
-0.06
the result of the X-ray structural analysis, the theoretical
calculations revealed that 8a is more stable than 8b by 4.3
kcal mol-1. Furthermore, the conformation of the optimized
structure for 8b was different from that of the X-ray structure
(Figures 4 and 6). Taking these results into consideration,
the preference of the 8b-type structure in the crystalline state
may be interpreted in terms of the effects of the inter-
molecular interactions, which are observed in the X-ray
structural analysis (Figure 5).
On the other hand, the calculated structure for 8a showed
the longer distances between the central palladium atom and
the terminal sulfur atoms (Pd1‚‚‚S1 ) 3.575, Pd1‚‚‚S4 )
3.589 Å) compared with those in complex 7 (Figures 3 and
6). This difference may be explained in terms of the effects
of the bulky substituents; i.e., the steric hindrance of the Tbt
groups in 7 leads to the conformation suitable for the
a 0.1 M (n-Bu)4NPF6 in CH2Cl2. b 0.1 M (n-Bu)4NPF6 in THF.
coordination of the two terminal sulfur atoms to the central
palladium atom.
Interestingly, the 13C NMR spectrum of complex 8 in
CDCl3 at room temperature indicated that complex 8 has C2
symmetry. This result suggests that 8 has the 8a-type
structure in solution, which is consistent with not the X-ray
structure but the results of theoretical calculations. However,
we cannot exclude a possibility of the existence of the rapid
equilibrium among isomers such as 8a,b in solution within
the time scale of 13C NMR spectrometry at room tempera-
ture.21
Electrochemistry of Palladium(II) Complexes 7 and 8.
As described in the Introduction, the cyclic polythioether
ligands have been known to stabilize mononuclear palla-
dium(III) species,4 which are generally known to be unstable.
We investigated the electrochemical properties of complexes
7 and 8, comparing with those of [PdCl2{PhS(o-phenylene)-
SPh}] (9).19 The redox potentials of 7-9 were summarized
in Table 2. The cyclic voltammogram of 7 showed a
chemically reversible one-electron oxidation [E1/2 ) -0.29
V (0.1 M (n-Bu)4NPF6 in CH2Cl2) or E1/2 ) -0.09 V (0.1
M (n-Bu)4NPF6 in THF) vs Fc/Fc+ (ferrocene/ferrocenium)]
and an irreversible reduction [Epc ) -1.84 V (0.1 M (n-
Bu)4NPF6 in THF) vs Fc/Fc+]. Since the E1/2 values in the
oxidation of 7 are close to those in the reversible one-electron
oxidation of 9 [E1/2 ) -0.22 V (0.1 M (n-Bu)4NPF6 in
CH2Cl2) or E1/2 ) -0.06 V (0.1 M (n-Bu)4NPF6 in THF) vs
Fc/Fc+], both these oxidations of 7 and 9 may be assigned
to Pd(II)/Pd(III) couples as well as the case of the Pd
complexes with crown thioethers.1b,3 The differential pulse
voltammograms of 7 and 9 suggested that the irreversible
reduction waves of 7 and 9 are one- and two-electron
processes, respectively, indicating that these reductions may
be assigned to different processes. On the other hand, cyclic
voltammograms of 8 showed irreversible oxidation and
reduction at Epa ) +0.97 V (0.1 M (n-Bu)4NPF6 in CH2Cl2)
and Epc ) -1.18 V (0.1 M (n-Bu)4NPF6 in THF) vs Fc/Fc+,
respectively. It is interesting that the redox process of 8 is
considered to be completely different from those of 7.
Figure 5. Intermolecular interaction in the crystalline state of 8. Selected
intermolecular C-C distances (Å): C14‚‚‚C14* 3.461(3), C29‚‚‚C2*
3.599(5), C14‚‚‚C21* 3.582(4), C15‚‚‚C21* 3.477(4), C15‚‚‚C22* 3.460(4).
Figure 6. (a) Theoretically optimized structure of 8a. Selected bond
distances (Å) and angles (deg): Pd1-S2 ) 2.377, Pd1-S3 ) 2.377, Pd1-
Cl1 ) 2.373, Pd1-Cl2 ) 2.373, Pd1‚‚‚S1 ) 3.575, Pd1‚‚‚S4 ) 3.589;
S2-Pd1-S3 ) 88.323, S2-Pd1-Cl1 ) 89.054, Cl1-Pd1-Cl2 ) 94.085,
S3-Pd1-Cl2 ) 89.026, S1-Pd1-S2 ) 65.8, S1-Pd1-S3 ) 73.0, Cl1-
Pd1-S1 ) 101.0, Cl2-Pd1-S1 ) 118.5, S4-Pd1-S2 ) 72.2, S4-Pd1-
S3 ) 65.6, Cl1-Pd1-S4 ) 118.5, Cl2-Pd1-S4 ) 101.7. (b) Theoretically
optimized structure of 8b. Selected bond distances (Å) and angles (deg):
Pd1-S1 ) 2.383, Pd1-S2 ) 2.369, Pd1-Cl1 ) 2.375, Pd1-Cl2 ) 2.366,
Pd1‚‚‚S3 ) 3.537, S1-Pd1-S2 ) 88.331; S1-Pd1-Cl1 ) 88.313, S2-
Pd1-Cl2 ) 88.757, Cl1-Pd1-Cl2 ) 94.742.
(21) The 13C DEPT 90 NMR spectra of 8 at low temperatures (0, -20,
-40, and -60 °C) showed the upper or lower field shifts of some
signals and the appearance of some new peaks. However, these
measurements did not lead to the observation of splitting of the
signals, which indicates the existence of the rapid equilibrium
among isomers such as 8a,b. These spectroscopic behaviors could not
be analyzed in detail, though suggesting the existence of some
equilibrium.
Inorganic Chemistry, Vol. 44, No. 23, 2005 8565

Takeda et al.
trode, a Pt wire counter electrode, and Ag/0.01 M AgNO3 in 0.1
M n-Bu4NPF6/CH3CN reference electrode. The measurements were
carried out in CH2Cl2 and THF solution containing 0.1 M
n-Bu4NPF6 as a supporting electrolyte with scan rates of 50-300
mV s-1 at ambient temperature.
Conclusion
A new tetrathioether ligand 1 tethered with two bulky
substituents, Tbt groups, was synthesized by taking advantage
of the coupling reaction of thiols with iodobenzenes using
Cu2O in 2,4,6-trimethylpyridine. Complexation of 1 with
Na2PdCl4 gave the corresponding dichloropalladium complex
7, the X-ray structural analysis of which indicated its
distorted octahedral structure with weak intramolecular
interactions between the two terminal sulfur atoms and the
central palladium metal.
On the other hand, a phenyl-substituted tetrathioether
ligand 2 reacted with Na2PdCl4 to give the corresponding
dichloropalladium complex 8. X-ray crystallography revealed
the structure of complex 8 in the crystalline state, where the
dichloropalladium part is coordinated by the one terminal
sulfur atom and the neighboring sulfur atom of 2. By contrast,
the 13C NMR spectrum of 8 in CDCl3 at room temperature
suggested a type of structure in solution different from that
in the crystalline state, i.e., the 8a-type structure, where the
two inner sulfur atoms of 2 coordinate to the central metal.
However, a possibility of the existence of rapid equilibriums
among isomers such as 8a,b in solution within the time scale
of 13C NMR spectrometry could not be excluded.
We wish to propose a possible explanation for the distorted
octahedral structure of 7 in the crystalline state as follows.
Ligand 1 preferably has a conformation, in which the C-S
(terminal)-C planes are almost perpendicular to the benzene
rings of the Tbt groups and almost parallel to the neighboring
o-phenylene rings, because of the steric effects of the bulky
Tbt groups. It is considered that ligand 1 with this conforma-
tion can effectively stabilize the distorted octahedral structure.
Further studies on the properties and applications of the
dichloropalladium complexes 7 and 8 are very interesting.
In addition, the ligands 1 and 2 are expected to be useful
for the synthesis of unusual complexes.
Synthesis of 2,4,6-Tris[bis(trimethylsilyl)methyl]benzenethiol
(3). To a THF solution (120 mL) of TbtBr22 (7.54 g, 11.9 mmol)
was gradually added t-BuLi (2.2 M pentane solution, 11.9 mL, 26.2
mmol) at -78 °C. After the yellow solution was stirred for 1 h at
this temperature, S8 (1.14 g, 4.46 mmol) was added. The reaction
mixture was stirred at -78 °C for 1 h and then at room temperature
for 3 h. The resulting dark brown solution was poured into ice water.
The mixture was extracted with hexane (200 mL), and the organic
layer was dried with MgSO4. After removal of the solvents under
reduced pressure, reprecipitation from CH2Cl2/CH3CN gave thiol
3 (6.27 g, 10.7 mmol, 90%) as colorless crystals. 3: colorless solid;
1
mp 167.8-169.8 °C; H NMR (300 MHz, CDCl3) δ -0.01 (s,
36H), 0.00 (s, 18H), 1.27 (s, 1H), 2.39 (s, 1H), 2.70 (s, 1H), 2.82
(s, 1H), 6.32 (s, 1H), 6.44 (s, 1H); 13C NMR (75 MHz, CDCl3) δ
0.4 (q), 0.6 (q), 28.0 (d × 2), 30.0 (d), 120.8 (s), 121.8 (d), 126.6
(d), 141.6 (s), 146.8 (s × 2); HRMS (EI; m/z) found 584.3018
([M]+), calcd for C27H60SSi6 584.3031. Anal. Calcd for C27H60-
SSi6: C, 55.40; H, 10.33. Found: C, 55.26; H, 10.27.
Synthesis of 2-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenylthio}-
iodobenzene (5). To a mixture of thiol 3 (6.0 g, 10.3 mmol) and
Cu2O (1.54 g, 10.8 mmol) in 2,4,6-trimethylpyridine (35 mL) was
added 1,2-diiodobenzene (1.34 mL, 10.3 mmol), and the mixture
was refluxed for 3 h. The reaction mixture was passed through a
short column (SiO2, hexane) to remove inorganic salts. All fractions
were collected and washed with a 0.2 M aqueous solution of HCl
three times (100 mL × 3). The organic layer was dried with MgSO4
and evaporated. The addition of EtOH to the resulting orange oil
led to the formation of colorless precipitates, and the filtration of
the mixture gave sulfide 5 (4.18 g, 5.31 mmol, 52%) as colorless
1
crystals. 5: colorless solid; mp 188.1-190.1 °C; H NMR (300
MHz, CDCl3) δ -0.03 (s, 36H), 0.06 (s, 18H), 1.37 (s, 1H), 2.60
(s, 2H), 6.41 (s, 1H), 6.54 (s, 1H), 6.65 (dd, J ) 1.5, 7.8 Hz, 1H),
6.71-6.78 (m, 1H), 7.01-7.08 (m, 1H), 7.74 (dd, J ) 1.3, 7.9 Hz,
1H); 13C NMR (75 MHz, CDCl3) δ 0.7 (q), 0.8 (q), 26.7 (d × 2),
30.7 (d), 96.4 (s), 122.5 (d), 126.1 (s), 126.2 (d), 127.3 (d), 128.1
(d), 128.4 (d), 139.1 (d), 143.7 (s), 144.8 (s), 150.1 (s × 2); HRMS
(EI; m/z) found 786.2306 ([M]+), calcd for C33H63ISSi6 786.2311.
Anal. Calcd for C33H63ISSi6: C, 50.34; H, 8.07. Found: C, 50.47;
H, 8.10.
Synthesis of 1,2-Bis(2-{2,4,6-tris[bis(trimethylsilyl)methyl]-
phenylthio}phenylthio)benzene (1). A red-purple suspension of
sulfide 5 (1.0 g, 1.27 mmol), Cu2O (186 g, 1.30 mmol), and 1,2-
benzenedithiol (90 mg, 0.635 mmol) in 2,4,6-trimethylpyridine (13
mL) was refluxed for 3 h. The reaction mixture was subjected to
short column chromatography (SiO2, benzene) to remove inorganic
salts. Hexane (100 mL) was added to the eluate, and then the
mixture was washed with a 0.2 M aqueous solution of HCl three
times (100 mL × 3). After drying with MgSO4, the solvents were
removed under reduced pressure to give an orange oil. The addition
of EtOH to the residue resulted in the formation of colorless
precipitates, and the filtration of the mixture gave pure tetrathioether
1 (743 mg, 0.51 mmol, 80%) as colorless crystals. 1: colorless
blocks; mp: 211.0-212.0 °C; 1H NMR (300 MHz, CDCl3) δ 0.03
(s, 72H), 0.08 (s, 36H), 1.38 (s, 2H), 2.66 (s, 4H), 6.43 (s, 2H),
6.58 (s, 2H), 6.61-6.66 (m, 2H), 6.93-7.04 (m, 4H), 7.05-7.16
Experimental Section
General Procedures. All reactions were carried out under an
argon atmosphere, unless otherwise noted. THF was purified by
distillation from sodium diphenylketyl before use. Preparative gel
permeation liquid chromatography (GPLC) was performed on an
LC-908 or LC-918 instrument with JAI gel 1H+2H columns (Japan
Analytical Industry) using chloroform or toluene as an eluent. Wet
column chromatography (WCC) and short column chromatography
were performed with Nacalai Tesque silica gel 60. The H NMR
(300 MHz) and 13C NMR (75 MHz) spectra were measured in
CDCl3 with a JEOL AL-300 spectrometer using CHCl3 (7.25 ppm)
1
1
as internal standards for H NMR spectroscopy and CDCl3 (77.0
ppm) as those for 13C NMR spectroscopy. High-resolution mass
spectral data were obtained on a JEOL JMS-700 spectrometer. The
electronic spectra were recorded on a JASCO V-570 UV/vis
spectrometer, and diffuse UV/vis reflectance spectra were recorded
on a JASCO V-570 UV/vis spectrometer equipped with an
integrating sphere accessory. All melting points were determined
on a Yanaco micro melting point apparatus and are uncorrected.
Elemental analyses were performed by the Microanalytical Labora-
tory of the Institute for Chemical Research, Kyoto University. The
electrochemical experiments were carried out with an ALS 602A
potentiostat/galvanostat using a glassy carbon disk working elec-
(22) Okazaki, R.; Tokitoh, N.; Matsumoto, T. In Synthetic Methods of
Organometallic and Inorganic Chemistry; Auner, N., Klingebiel, U.,
Eds.; Thieme: New York, 1996; Vol. 2, pp 260-269.
8566 Inorganic Chemistry, Vol. 44, No. 23, 2005

A Distorted Octahedral Pd(II)-Tetrathioether Complex
(m, 4H), 7.20-7.25 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 0.8
(q), 0.9(q), 26.3 (d × 2), 30.6 (d), 122.7 (d), 123.9 (s), 125.2 (d),
127.3 (d), 127.5 (d), 127.6 (d), 127.7 (d), 130.3 (s), 130.6 (d), 132.8
(d), 137.0 (s), 142.1 (s), 144.4 (s), 150.4 (s × 2); HRMS (FAB;
m/z) found m/z 1458.6298 ([M]+), calcd for C72H130S4Si12 1458.6287.
Anal. Calcd for C72H130S4Si12‚CHCl3: C, 55.48; H, 8.35. Found:
C, 55.27; H, 8.34.
Synthesis of [PdCl2(2)] (8). Tetrathioether 2 (25.0 mg, 0.0489
mmol) was dissolved into EtOH (10 mL) by heating at reflux. To
the solution was added Na2PdCl4 (14.4 mg, 0.0489 mmol) using
EtOH (3 mL). Heating of the orange solution at 60 °C for 5 min
resulted in the formation of orange precipitates, and the resulting
orange suspension was further refluxed for 30 min. After evapora-
tion of the solvents, CH2Cl2 (100 mL) was added to the residue
and the resulting orange suspension was filtered through Celite.
The orange filtrate was evaporated to give pure palladium dichloride
complex 8 (34.1 mg, quant) as orange crystals. 8: orange plates;
Synthesis of 2-Iodophenyl Phenyl Sulfide (6). A red-purple
suspension of benzenethiol (4) (3.51 mL, 34.2 mmol), Cu2O (4.80
g, 33.6 mmol), and 1,2-diiodobenzene (11.1 g, 33.6 mmol) in 2,4,6-
trimethylpyridine (170 mL) was refluxed for 3 h. After addition of
150 mL of hexane, the mixture was washed with 0.2 M aqueous
solution of HCl four times (100 mL × 4). The organic layer was
dried with MgSO4 and evaporated. The residue was separated with
WCC (SiO2, hexane) to give sulfide 6 (3.7 g, 11.8 mmol, 35%) as
colorless crystals. 6:23 colorless solid; mp 52-53 °C; 1H NMR (300
MHz, CDCl3) δ 6.87 (dd, J ) 7.8, ∼8 Hz, 1H), 6.95 (d, J ) 7.8
Hz, 1H), 7.19 (dd, J ) 7.8, ∼8 Hz, 1H), 7.34-7.47 (m, 5H), 7.83
(d, J ) 7.8 Hz, 1H).
Synthesis of 1,2-Bis[2-(phenylthio)phenylthio]benzene (2). A
red-purple suspension of sulfide 6 (3.69 g, 11.8 mmol), Cu2O (1.69
g, 11.8 mmol), and 1,2-benzenedithiol (841 mg, 5.91 mmol) in
2,4,6-trimethylpyridine (20 mL) was refluxed for 3 h. The reaction
mixture was subjected to short column chromatography (SiO2,
benzene) to remove inorganic salts. After addition of hexane (150
mL), the mixture was washed with a 0.2 M aqueous solution of
HCl four times (100 mL × 4). The organic layer was dried with
MgSO4 and evaporated under reduced pressure. The residue was
subjected to WCC (SiO2, hexane) and reprecipitated from CH2Cl2/
CH3CN to give polythioether 2 (768 mg, 1.50 mmol, 25%) as
colorless crystals. 2: colorless solid; mp 107.7-108.7 °C; 1H NMR
(300 MHz, DMSO-d6) δ 7.12-7.22 (m, 6H), 7.26-7.47 (m, 16H);
13C NMR (75 MHz, CDCl3) δ 127.3 (d), 127.5 (d), 127.8 (d), 128.0
(d), 129.2 (d), 131.0 (d), 131.4 (d), 132.0 (d), 132.2 (d), 134.2 (s),
135.1 (s), 136.6 (s), 138.8 (s); HRMS (EI; m/z) found 510.0594
([M]+), calcd for C30H22S4 510.0604. Anal. Calcd for C30H22S4:
C, 70.55; H, 4.34. Found: C, 70.63; H, 4.29.
1
mp 295.2-305.2 °C (dec); H NMR (300 MHz, CDCl3) δ 6.97-
7.67 (m, 22H); 13C NMR (75 MHz, CDCl3) δ 127.48 (d), 127.51
(d), 127.9 (d), 128.0 (d), 129.3 (d), 131.4 (d), 131.8 (d), 132.1 (d),
132.4 (d), 134.7 (s), 135.8 (s), 137.1 (s), 139.1 (s); UV-vis (CHCl3)
λmax 417 (ꢀ 3.6 × 103), 308 (sh, 1.4 × 103), 289 (sh, 9.8 × 102);
HRMS (FAB; m/z) found 650.9342 ([M - Cl]+), calcd for
C30H2235Cl106PdS4 ([M - Cl]+) 650.9328.
X-ray Structural Analysis of 1‚CHCl3, 2, 7‚2(CH2Cl2), and
8. Single crystals of 1‚CHCl3, 2, 7‚2(CH2Cl2), and 8 suitable for
X-ray structural analysis were obtained by slow recrystallization
from CHCl3/CH3CN, benzene, CH2Cl2/CH3CN, and CH2Cl2/EtOH,
respectively. The crystals were mounted on a glass fiber. The
intensity data were collected on Rigaku/MSC Mercury CCD
diffractometer with graphite-monochromated Mo KR radiation (λ
) 0.710 69 Å for 1‚CHCl3 and λ ) 0.710 70 Å for 2, 7‚2(CH2Cl2),
and 8). The structures were solved by direct methods (SIR-97)24
(for 1‚CHCl3, 2, and 8) and Patterson methods (DIRDIF)25 (for
7‚2CH2Cl2) and refined by full-matrix least-squares procedures on
F2 for all reflections (SHELXL-97).26 All the non-hydrogen atoms
were refined anisotropically. All hydrogens for 1‚CHCl3 and
7‚2(CH2Cl2) were placed using AFIX instructions, and those for 2
and 8 were refined isotropically. The structural data are shown in
Table 3. In the analysis of 7‚2CH2Cl2, there are the highest peak
(1.559 e Å-3) and the deepest hole (-1.634 e Å-3) near the CH2Cl2
solvent molecule due to disorders that could not be completely
solved.
Theoretical Calculations. All theoretical calculations were
carried out using the Gaussian 98 program27 with density functional
theory at the B3LYP level.20 The LANL2DZ basis sets for Pd were
used with effective core potential, and the 6-31G(d) basis sets were
used for C, H, S, and Cl atoms. The LANL2DZ(ECP) basis sets
were obtained from the Extensible Computational Chemistry
Environment Basis Set Database (http://www.emsl.pnl.gov/forms/
basisform.html), version 02/25/04, as developed and distributed by
Synthesis of [PdCl2(1)] (7). Tetrathioether 1 (100 mg, 0.0684
mmol) was dissolved into EtOH (40 mL) by heating at reflux. To
the solution was added Na2PdCl4 (40.3 mg, 0.137 mmol) using 3
mL of EtOH. The red solution was refluxed for 5 min, and the
resulting orange suspension was further heated at reflux for 30 min.
After evaporation of the solvents, CHCl3 (20 mL) was added to
the residue and the resulting orange suspension was filtered through
Celite. The orange filtrate was evaporated to give pure palladium
dichloride complex 7 (114.2 mg, quantitative). 7: orange blocks;
(24) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giaco-
vazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115-119.
(25) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Garcia-Granda, S.;
Gould, R. O.; Israel, R.; Smits, J. M. M. The DIRDIF-99 program
system; Crystallography Laboratory, University of Nijmegen: Nijmegen,
The Netherlands, 1999.
1
mp 254.2-259.2 °C (dec); H NMR (300 MHz, CDCl3, 50 °C) δ
-0.10 (s, 36H), 0.09 (s, 72H), 1.41 (s, 2H), 2.06 (s, 2H), 2.78 (s,
2H), 6.52 (s, 4H), 6.55 (dd, 3J ) 7.8, 4J ) 1.5 Hz, 2H), 7.13 (ddd,
3J ) 7.6, ∼8 Hz, 4J ) 1.5 Hz, 2H), 7.20-7.26 (ddd, 3J ) 7.8, ∼8
4
3
Hz, J ) 0.8 Hz, 2H), 7.39-7.43 (m, 4H), 7.83 (dd, J ) 7.6 Hz,
4J ) 0.8 Hz, 2H); 13C NMR (75 MHz, CDCl3, 50 °C) δ 0.5 (q),
0.8 (q), 1.4 (q), 26.5 (d), 27.2 (d), 30.9 (d), 120.4 (s), 123.2 (d),
124.3 (d), 127.8 (d), 128.1 (s), 128.3 (d), 130.6 (d), 131.3 (d), 132.1
(d), 135.9 (s), 136.3 (d), 142.8 (s), 145.8 (s), 149.9 (s), 151.8 (s);
UV-vis (CHCl3) λmax 398 (ꢀ 6.5 × 103), 305 (sh, 7.6 × 103), 294
(sh, 5.3 × 103); LRMS (ESI; m/z) found 1600 ([M - Cl]+), calcd
for C72H13035Cl106PdS4Si12 ([M - Cl]+) 1600. Anal. Calcd for
C72H130ClPdS4Si12‚CHCl3: C, 49.88; H, 7.51. Found: C, 49.73;
H, 7.42.
(26) Sheldrick, G. M. SHELX-97, Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(27) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels,
A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone,
V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Salvador, P.; Dannenberg, J. J.; Malick, D. K.; Rabuck,
A. D.; Raghavachari, K.; Foresman, J. B.; Cioslowski, J.; Ortiz, J.
V.; Baboul, A. G.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Gomperts, R.; Martin, R. L.; Fox, D. J.; Keith, T.;
Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.;
Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Andres, J. L.;
Gonzalez, C.; Head-Gordon, M.; Replogle, E. S.; Pople, J. A. Gaussian
98; Gaussian, Inc.: Pittsuburgh, PA, 1998.
(23) Beringer, F. M.; Kravetz, L.; Topliss, G. B. J. Org. Chem. 1965, 30,
1141-1148.
Inorganic Chemistry, Vol. 44, No. 23, 2005 8567

Takeda et al.
Table 3. Crystal Data and Refinement Details for 1‚CHCl3, 2, 7‚2CH2Cl2, and 8
param
empirical formula
1‚CHCl3
2
7‚2(CH2Cl2)
8
C72H130S4Si12‚CHCl3
1580.45
C30H22S4
510.72
C72H130Cl2PdS4Si12‚2CH2Cl2
1808.23
C30H22Cl2PdS4
fw
688.02
temp (K)
cryst system
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
103(2)
103(2)
triclinic
103(2)
103(2)
triclinic
monoclinic
P21 (No. 4)
14.0803(6)
16.5775(7)
19.9887(9)
90
90.613(3)
90
4665.4(3)
2
1.125
0.377
0.40 × 0.25 × 0.03
1.78-25.50
27 097
monoclinic
C2/c (No. 15)
41.273(3)
12.8906(6)
19.3198(11)
90
105.752(2)
90
9892.9(10)
4
1.214
0.615
0.35 × 0.20 × 0.10
1.91-25.00
39 657
P1h (No. 2)
7.5404(10)
10.4513(16)
16.759(3)
88.513(6)
78.037(5)
71.784(4)
1226.2(3)
2
1.383
0.406
0.40 × 0.20 × 0.10
2.36-26.00
8636
P1h (No. 2)
9.4221(18)
10.779(2)
14.826(3)
80.988(7)
76.200(7)
73.758(5)
1397.5(5)
2
1.635
1.174
0.20 × 0.10 × 0.05
2.63-25.00
9167
D
calc (Mg m-3
)
abs coeff (mm-1
cryst size (mm)
θ range (deg)
)
no. of reflcns measd
no. of indep reflcns
Rint
14 849
0.0834
4661
0.0126
8658
0.0219
4828
0.0191
completeness (%)
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]a
98.90
14 849/1/865
1.005
R1 ) 0.0636
wR2 ) 0.1540
R1 ) 0.0930
wR2 ) 0.1757
-0.10(9)
0.576 and -0.661
96.70
4661/0/395
1.051
R1 ) 0.0306
wR2 ) 0.0738
R1 ) 0.0332
wR2 ) 0.0754
99.20
8658/0/456
1.079
R1 ) 0.0549
wR2 ) 0.1393
R1 ) 0.0576
wR2 ) 0.1414
97.80
4828/0/422
1.092
R1 ) 0.0290
wR2 ) 0.0571
R1 ) 0.0349
wR2 ) 0.0594
R indices (all data)a
absolute struct param
largest diff peak and hole (e Å-3
)
0.537 and -0.269
1.559 and -1.634
0.600 and -0.298
2
2
2
a R1 ) Σ||Fo| - |Fc||/Σ|Fo|, wR2 ) [(Σw(Fo - Fc )2/Σw(Fo )2]1/2
.
the Molecular Science Computing Facility, Environmental and
Molecular Sciences Laboratory, which is part of the Pacific
Northwest Laboratory, P.O. Box 999, Richland, WA 99352, and
funded by the U.S. Department of Energy. The Pacific Northwest
Laboratory is a multiprogram laboratory operated by Battelle
Memorial Institute for the U.S. Department of Energy under
Contract DE-AC06-76RLO 1830. Contact Karen Schuchardt for
further information. Computation time was provided by the
Supercomputer Laboratory, Institute for Chemical Research, Kyoto
University.
Program on Kyoto University Alliance for Chemistry, from
the Ministry of Education, Culture, Sports, Science, and
Technology of Japan. We are grateful to Assistant Professor
Takahiro Sasamori, and Dr. Noriyoshi Nagahora, Institute
for Chemical Research, Kyoto University, for the valuable
discussions.
Supporting Information Available: Crystallographic informa-
tion files (CIF) for the compounds 1‚CHCl3, 2, 7‚2(CH2Cl2), and
8, atomic coordinates for the calculated molecules 8a,b, VT-13C
DEPT 90 NMR spectra of 8 (at 50, 25, 0, -20, -40, and -60
°C), and cyclic voltammograms of 7-9. This material is available
free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. This work was partially supported by
Grants-in-Aid for COE Research on Elements Science (No.
12CE2005), Creative Scientific Research (17GS0207), Sci-
entific Research on Priority Area (No. 14078213), Young
Scientist (B) (No. 15750031), and 21st Century COE
IC050944V
8568 Inorganic Chemistry, Vol. 44, No. 23, 2005