Synthesis and structure of group 10 metal complexes with new tripodal tetradentate ligand bearing one phosphine and three thioether moieties

Article abstract of DOI:10.1246/bcsj.20090187

A new tripodal tetradentate ligand bearing one phosphine and three thioether moieties, [2-(i-PrS)C₆H₄]₃P(1b), was synthesized by the reaction of [2-(i-PrS)C₆H₄]Li with PCl₃ in good yield. Ligand 1b reacted with NiCl₂· 6H₂O in the presence of NaBF₄ to afford a five-coordinate complex, [NiCl(1b)]BF₄ (2), with slightlydistorted trigonal-bipyramidal geometry. Reaction of 1b with [PdCl₂(PhCN) ₂] gave a five-coordinate complex, [PdCl(1b)]Cl (3a). Anion-exchange reaction of palladium(II) complex 3a with NaBF₄ afforded [PdCl(1b)]BF₄ (3b)with distorted trigonal-bipyramidal structure. Reaction of 1b with [PtCl₂(cod)] resulted in the formation of a four-coordinate square-planar complex, [PtCl₂(1b)] (4). The structures of 2, 3b, and 4 in crystalline state were determined by X-ray structural analysis and are described in detail. The structures of 2-4 in solution were also discussed.

Full text of DOI:10.1246/bcsj.20090187

© 2010 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 83, No. 2, 157–164 (2010)
157
Synthesis and Structure of Group 10 Metal Complexes
with New Tripodal Tetradentate Ligand Bearing
One Phosphine and Three Thioether Moieties
Nobuhiro Takeda,* Yusuke Tanaka, Fumiaki Sakakibara, and Masafumi Unno*
Department of Chemistry and Chemical Biology, Graduate School of Engineering,
Gunma University, 1-5-1 Tenjin-cho, Kiryu 376-8515
International Education and Research Center for Silicon Science, Graduate School of Engineering,
Gunma University, 1-5-1 Tenjin-cho, Kiryu 376-8515
Received July 21, 2009; E-mail: ntakeda@chem-bio.gunma-u.ac.jp
A new tripodal tetradentate ligand bearing one phosphine and three thioether moieties, [2-(i-PrS)C6H4]3P (1b), was
synthesized by the reaction of [2-(i-PrS)C6H4]Li with PCl3 in good yield. Ligand 1b reacted with NiCl2¢6H2O in the
presence of NaBF4 to afford a five-coordinate complex, [NiCl(1b)]BF4 (2), with slightly distorted trigonal-bipyramidal
geometry. Reaction of 1b with [PdCl2(PhCN)2] gave a five-coordinate complex, [PdCl(1b)]Cl (3a). Anion-exchange
reaction of palladium(II) complex 3a with NaBF4 afforded [PdCl(1b)]BF4 (3b) with distorted trigonal-bipyramidal
structure. Reaction of 1b with [PtCl2(cod)] resulted in the formation of a four-coordinate square-planar complex,
[PtCl2(1b)] (4). The structures of 2, 3b, and 4 in crystalline state were determined by X-ray structural analysis and are
described in detail. The structures of 2-4 in solution were also discussed.
In recent years, much attention has been focused on the
chemistry of transition-metal complexes bearing tripodal
tetradentate ligands from the viewpoints of the activation of
small molecules, the stabilization of reactive species with
unusual electric and geometric structures, catalytic activities,
and so on.1 Although there are many reports on tripodal
tetradentate ligands bearing nitrogen or phosphorus atoms, the
chemistry of those bearing one phosphine and three thioether
moieties is less explored. Such ligands are expected to show
unique structures and reactivities derived from the lability of
the coordination of thioether moieties to metals and the
property of phosphine as an anchor ligand. Tris(2-methylthio-
phenyl)phosphine (1a) (Chart 1) has been only reported as
phosphine ligands tethered with three thioether moieties so far,
and there have been several papers on the synthesis and
structures of its complexes with nickel(II),2-5 palladium(II),6,7
platinum(II),7 molybdenum(0), and molybdenum(II)8 metals
and the use of 1a as a ligand in a rhodium-catalyzed reaction.9
Meek and co-workers have reported that the methyl-
substituted ligand 1a forms five-coordinate trigonal-bipyram-
idal complexes with nickel(II), [NiX(1a)]ClO4 (X = Cl, Br, I,
and NCS) and [Ni(1a)L](ClO4)2 (L = S=C(NH2)2, PPh3, and
PMePh2).2,4 In the case of the palladium(II) complexes, they
have isolated only four-coordinate square-planer complexes,
[PdCl2(1a)]¢dmf, [Pd(1a)2](ClO4)2, [Pd2Cl4(1a)],6,7 although
the UV-vis spectra of these palladium(II) complexes in
solution fit the trends of five-coordinate complexes. Their
numerous attempts to isolate a pure five-coordinate complex,
[PdCl(1a)]ClO4, have been unsuccessful owing to the precip-
itation of insoluble [Pd(1a)2](ClO4)2 and [Pd2Cl4(1a)]. As for a
platinum(II) complex of 1a, only a four-coordinate square-
planar bis(chelate) complex, [Pt(1a)2](ClO4)2, where 1a func-
tions as a bidentate ligand, has been synthesized.7 The struc-
tures of these complexes are determined by spectroscopic data
and elemental analyses, and the X-ray structural analyses have
5
been only reported for [NiCl(1a)]ClO4 and [Pd(1a)2](ClO4)2.7
From these results, we considered that the replacement of
methyl groups on the sulfur atoms in ligand 1a by bulky groups
can suppress the formation of bis(chelate) complexes such as
[Pd(1a)2]+ and [Pt(1a)2]+ and lead to the isolation of the
corresponding five-coordinate complexes. In this work, we
describe the synthesis and structure of the isopropyl-substituted
ligand 1b and its coordination chemistry with group 10 metals.
R
R
Experimental
S
S
1a: R = Me
1b: R = i-Pr
General Procedures. All reactions were carried out under an
argon atmosphere unless otherwise noted. Tetrahydrofuran was
purified by distillation from sodium diphenyl ketyl before use. Wet
column chromatography (WCC) was performed with Merck Silica
Gel 60 (70-230 mesh ASTM). The 1H NMR (500 MHz), 13C NMR
(126 MHz), and 31P NMR (202 MHz) spectra were measured in
CDCl3 with a JEOL JNM--500 spectrometer using SiMe4 (0 ppm)
P
S
R
Chart 1.
Published on the web January 29, 2010; doi:10.1246/bcsj.20090187

158
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
Metal Complexes with New Tripodal Ligand
as internal standards for 1H NMR spectroscopy, CDCl3 (77.0 ppm)
as those for 13C NMR spectroscopy, and H3PO4 (85%) in D2O
(0 ppm) as an external standard for 31P NMR spectroscopy. The
UV-vis spectra were recorded on a Shimadzu UV-2500PC UV-vis
spectrometer. All melting points were determined on a Yanaco
micro melting point apparatus MP-J3 and are uncorrected.
Elemental analyses were performed by the Center for Material
Research by Instrumental Analysis (CIA), Gunma University.
Preparation of Tris(2-isopropylthiophenyl)phosphine (1b).
To a mixture of hexane (15 mL), isopropyl phenyl sulfide10 (1.00 g,
6.57 mmol), and TMEDA (2.0 mL, 13.1 mmol) was added a hexane
solution of butyllithium (1.65 M, 4.79 mL, 7.90 mmol) at 25 °C.
After heating at 50 °C for 1 h, the mixture was cooled to ¹40 °C,
and PCl3 (0.23 mL, 2.63 mmol) was added at this temperature. The
reaction mixture was stirred at ¹40 °C for 3 h, then warmed to 25 °C
over 12 h. After addition of a saturated aqueous solution of NH4Cl,
the mixture was extracted with hexane/chloroform (1:1), and the
organic layer was dried over anhydrous MgSO4. The solvents were
removed under reduced pressure, and the residue was separated
by WCC (SiO2, hexane:chloroform = 1:1) to afford pure tris(2-
isopropylthiophenyl)phosphine (1b) (1.02 g, 2.10 mmol, 96%). 1b:
1JCP = 60 Hz), 133.9 (d, 2JCP = 13 Hz, CH), 134.6 (CH), 136.4
2
(CH), 137.6 (d, JCP = 20 Hz); 31P{1H} NMR (202 MHz, CDCl3,
7.6 mM): ¤ 72.0; UV-vis (chloroform): -max 283 (¾ 10000), 364 (¾
3300), 495.5 (¾ 380) nm. Anal. Calcd for C27H33Cl2PPdS3¢2H2O:
C, 46.45; H, 5.34%. Found: C, 46.26; H, 5.35%.
Reaction of 3a¢2H2O with NaBF4. To 3a¢2H2O (0.10 g,
0.15 mmol) and NaBF4 (1.0 g, 9.1 mmol) was added dichloro-
methane (4 mL), and the mixture was stirred at 25 °C for 24 h.
After addition of a saturated aqueous solution of NH4Cl, the
mixture was extracted with dichloromethane, and the organic layer
was dried over anhydrous MgSO4. The solvent was removed under
reduced pressure, and the residue was reprecipitated from hexane/
chloroform to afford pure [PdCl{P[2-(i-PrS)C6H4]3}]BF4 (3b)
(97.2 mg, 0.14 mmol, 90%) as red crystals. 3b: red crystals, mp
208 °C (decomp.); 1H NMR (500 MHz, CDCl3, 7.0 mM): ¤ 1.29 (d,
3JHH = 7 Hz, 18H), 3.45 (sep, 3JHH = 7 Hz, 3H), 7.71 (ddd, 3JHH
=
8 Hz, 4JHH = 1 Hz, 4JPH = 4 Hz, 3H), 7.74 (dddd, 3JHH = 8 Hz,
3
3JHH = 8 Hz, 4JHH = 1 Hz, JPH = 3 Hz, 3H), 7.88 (dddd, JHH
=
8 Hz, 3JHH = 8 Hz, 4JHH = 1 Hz, JPH = 3 Hz, 3H), 8.20 (ddd,
3JHH = 8 Hz, 3JHP = 11 Hz, 4JHH = 1 Hz, 3H); 13C{1H} NMR
(126 MHz, CDCl3): ¤ 22.4 (CH3), 48.1 (CH), 132.0 (d, JCP = 8 Hz,
1
1
2
colorless crystals, mp 143-145 °C; H NMR (500 MHz, CDCl3):
CH), 132.4 (d, JCP = 65 Hz), 134.2 (d, JCP =13 Hz, CH), 135.0
¤ 1.26 (brs, 18H, CH3), 3.61 (sep, 3JHH = 7 Hz, 3H), 6.65 (d,
3JHH = 8 Hz, 3H), 7.12 (dd, 3JHH = 8, 8 Hz, 3H), 7.27 (dd,
3JHH = 8, 8 Hz, 3H), 7.53 (dd, 3JHH = 8 Hz, 2JHP = 4 Hz, 3H);
(CH), 135.4 (CH), 137.4 (d, JCP = 20 Hz); 31P NMR (202 MHz,
2
CDCl3, 7.0 mM): ¤ 81.0; UV-vis (chloroform): -max 284 (¾ 8700),
365 (¾ 3500), 499 (¾ 390) nm. Anal. Calcd for C27H33BClF4PPdS3:
C, 45.46; H, 4.66%. Found: C, 45.24; H, 4.89%.
13C{1H} NMR (126 MHz, CDCl3):
J
J
¤
23.1 (CH3), 40.0 (d,
CP = 7 Hz, CH), 127.8 (CH), 128.7 (CH), 134.1 (CH), 134.5 (d,
CP = 2 Hz, CH), 140.1 (d, 1JCP = 31 Hz), 143.3 (d, 2JCP = 11 Hz);
Reaction of 1b with [PtCl2(cod)]. To 1b (0.13 g, 0.27 mmol)
and [PtCl2(cod)]12 (0.10 g, 0.27 mmol) was added dichloromethane
(2 mL), and the mixture was stirred at 25 °C for 48 h. After
filtration of the reaction mixture, the filtrate was concentrated. The
residue was reprecipitated from hexane/chloroform to give
[PtCl2{P[2-(i-PrS)C6H4]3}] (4) (0.18 g, 0.24 mmol, 89%) as
31P{1H} NMR (202 MHz, CDCl3): ¤ ¹24.7. Anal. Calcd for
C27H33PS3: C, 66.90; H, 6.86%. Found: C, 66.93; H, 6.72%.
Reaction of 1b with NiCl2¢6H2O. To a mixture of 1b (0.10 g,
0.21 mmol), NiCl2¢6H2O (50 mg, 0.21 mmol), and NaBF4 (1.0 g,
9.1 mmol) was added dichloromethane (4 mL), and the mixture was
stirred at reflux for 72 h. After filtration of the reaction mixture, the
filtrate was concentrated. The residue was reprecipitated from
hexane/dichloromethane to give [NiCl{P[C6H4S(i-Pr)]3}]BF4 (2)
(0.13 g, 0.20 mmol, 95%) as blue crystals. 2: blue crystals, mp
220 °C (decomp.); 1H NMR (500 MHz, CDCl3, 7.5 mM): ¤ 1.31 (d,
3JHH = 7 Hz, 18H), 3.72 (sepd, 3JHH = 7 Hz, JPH = 2 Hz, 3H), 7.71
(dddd, 3JHH = 8 Hz, 3JHH = 8 Hz, 4JHH = 1 Hz, JPH = 2 Hz, 3H),
1
yellow crystals. 4: yellow crystals, mp 126 °C (decomp); H NMR
(500 MHz, CDCl3, 53 mM): ¤ 1.28 (brs, 18H), 3.56 (br, 3H), 7.2-
7.9 (m, 9H), 8.28 (brs, 3H); 13C{1H} NMR (126 MHz, CDCl3): ¤
22.1 (CH3), 48.0 (CH), 128.5 (CH), 131.3 (d, 1JCP = 82 Hz), 131.6
2
2
(CH), 133.8 (d, JCP = 10 Hz, CH), 134.8 (CH), 139.0 (d, JCP
=
9 Hz); 31P{1H} NMR (202 MHz, CDCl3): ¤ 50.3 (s, JPPt = 3150
Hz); UV-vis (chloroform): -max 283 (¾ 8140), 341 (¾ 1975) nm.
Anal. Calcd for C27H33Cl2PPtS3¢0.3CHCl3: C, 41.69; H, 4.27%.
Found: C, 41.63; H, 4.24%.
1
3
3
7.79 (dd, JHH = 8 Hz, JPH = 4 Hz, 3H), 7.92 (dddd, JHH = 8 Hz,
3JHH = 8 Hz, 4JHH = 1 Hz, JPH = 2 Hz, 3H), 8.59 (dd, 3JHH = 8 Hz,
J
X-ray Crystallography of 1b, 2, 3bi, 3bii, and 4. Single
crystals of 1b, 2, 3bi, 3bii, and 4 suitable for X-ray structural
analysis were obtained by slow recrystallization from hexane/
CHCl3. For 3b, two types of crystals, 3bi and 3bii, were obtained.
The crystals were mounted on a glass fiber. The intensity data were
collected on a Rigaku R-AXIS IV++ diffractometer with graphite
monochromated Mo K¡ radiation (- = 0.71070 ¡). The structures
were solved by direct methods (SHELXS-9713 or SIR-9714), and
refined by full-matrix least-squares procedures on F2 for all
reflections (SHELXL-9713). All the non-hydrogen atoms were
refined anisotropically. All hydrogens were placed using AFIX
instructions. The crystal data and refinement details are shown in
Tables 1 and 2. Crystallographic data have been deposited with
Cambridge Crystallographic Data Centre: Deposition numbers
CCDC-755459, CCDC-755460, CCDC-755461, CCDC-755462,
and CCDC-755463 for compounds 1b, 2, 3bi, 3bii, and 4,
respectively. Copies of the data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge, CB2 1EZ, U.K.; Fax: +44 1223 336033; e-mail:
deposit@ccdc.cam.ac.uk).
PH = 8 Hz, 3H); 13C{1H} NMR (126 MHz, CDCl3): ¤ 22.3 (CH3),
50.5 (CH), 133.1 (d, JCP = 7 Hz, CH), 133.1 (d, 2JCP = 27 Hz, CH),
133.6 (CH), 134.6 (CH), 135.2 (d, 1JCP = 64 Hz), 136.7 (d, 2JCP
=
25 Hz). 31P NMR (202 MHz, CDCl3, 7.5 mM): ¤ 102.3; UV-vis
(chloroform): -max 273 (¾ 10000), 334 (¾ 4300), 468 (¾ 250), 634
(¾ 1400) nm. Anal. Calcd for C27H33BClF4NiPS3: C, 48.72; H,
5.00%. Found: C, 48.36; H, 5.04%.
Reaction of 1b with [PdCl2(PhCN)2].
To 1b (0.25 g,
0.52 mmol) and [PdCl2(PhCN)2]11 (0.20 g, 0.52 mmol) was added
dichloromethane (4 mL), and the mixture was stirred at 25 °C for
72 h. After filtration of the reaction mixture, the filtrate was
concentrated. The residue was reprecipitated from hexane/chloro-
form to give [PdCl{P[2-(i-PrS)C6H4]3}]Cl¢2H2O (3a¢2H2O)
(0.26 g, 0.39 mmol, 76%) as red crystals. 3a¢2H2O: red crystals,
mp 113 °C (decomp.); 1H NMR (500 MHz, CDCl3, 60 mM): ¤ 1.30
(d, 3JHH = 7 Hz, 18H), 3.50 (sep, 3JHH = 7 Hz, 3H), 7.69-7.85 (m,
9H), 8.34-8.44 (m, 3H); 1H NMR (500 MHz, CDCl3, 7.6 mM):
3
3
¤ 1.29 (d, JHH = 7 Hz, 18H), 3.49 (sep, JHH = 7 Hz, 3H), 7.67
(br, 6H) 7.77 (br, 3H), 8.52 (br, 3H); 13C{1H} NMR (126 MHz,
CDCl3): ¤ 22.5 (CH3), 47.4 (CH), 131.4 (CH), 132.5 (d,

N. Takeda et al.
Table 1. Crystal Data and Refinement Details for 1b and 2
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
159
1b
2
Empirical formula
Formula weight
Temperature/K
Crystal system
Space group
a/¡
b/¡
c/¡
¡/°
¢/°
C27H33PS3
484.68
123(2)
[C27H33ClNiPS3]BF4
665.65
123(2)
monoclinic
P21/c (No. 14)
11.2735(5)
9.6868(5)
26.7013(11)
90
90.0725(5)
90
2915.9(2)
4
1.516
1.070
triclinic
ꢀ
P1 (No. 2)
10.5003(5)
15.5086(8)
16.4401(9)
90.853(3)
90.073(3)
92.902(3)
2673.5(2)
4
1.204
0.350
0.40 © 0.20 © 0.10
2.60 to 25.50°
18404
£/°
V/¡3
Z
D
¹3
calcd/Mg m
¹1
®(Mo K¡)/mm
Crystal size/mm3
ª range
0.30 © 0.15 © 0.15
2.24 to 25.50°
19381
5394
0.0207
No. of reflns measd
No. of indep reflns
Rint
9342
0.0277
Completeness
93.8%
99.4%
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2·(I)]a)
9342/0/559
1.318
5394/0/343
1.165
R1 = 0.0661
wR2 = 0.1223
R1 = 0.0676
wR2 = 0.1229
0.288 and ¹0.272
R1 = 0.0381
wR2 = 0.0761
R1 = 0.0383
wR2 = 0.0761
1.068 and ¹0.829
R indices (all data)a)
¹3
Largest diff./e ¡ peak and hole
2
2 2
2 2 1/2
a) R1 = -««Fo« ¹ «Fc««/-«Fo«, wR2 = [(-w(Fo ¹ Fc ) /-w(Fo ) ]
.
Table 2. Crystal Data and Refinement Details for 3bi, 3bii, and 4
3bi
3bii
4
Empirical formula
Formula weight
Temperature/K
Crystal system
Space group
a/¡
b/¡
c/¡
¡/°
[C27H33ClPPdS3]BF4 [C27H33ClPPdS3]BF4 [C27H33Cl2PPtS3]
713.34
713.34
750.67
123(2)
123(2)
123(2)
monoclinic
P21/c (No. 14)
9.8425(18)
13.6688(18)
23.137(3)
90
monoclinic
P21/c (No. 14)
11.2784(10)
9.7531(11)
26.855(3)
90
monoclinic
P21/n (No. 14)
8.7082(4)
18.2944(9)
18.3037(11)
90
¢/°
95.4931(19)
90
3098.5(8)
4
1.529
0.980
0.30 © 0.20 © 0.20
2.56 to 25.50°
20415
5718
0.0485
90.2427(14)
90
2954.0(5)
4
1.604
1.027
0.40 © 0.10 © 0.05
2.76 to 25.50°
19522
5356
0.0679
94.2085(7)
90
2908.1(3)
4
1.715
5.295
0.50 © 0.20 © 0.20
2.60 to 25.50°
17452
5103
0.0523
£/°
V/¡3
Z
¹3
Dcalcd/Mg m
¹1
®(Mo K¡)/mm
Crystal size/mm3
ª range
No. of reflns measd
No. of indep reflns
Rint
Completeness
99.1%
97.4%
94.1%
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2·(I)]a)
5718/0/343
1.312
5356/0/343
1.212
5103/0/307
1.193
R1 = 0.0761
wR2 = 0.1659
R1 = 0.0767
wR2 = 0.1663
0.788 and ¹1.398
R1 = 0.0523
wR2 = 0.1063
R1 = 0.0573
wR2 = 0.1089
1.129 and ¹1.101
R1 = 0.0442
wR2 = 0.1259
R1 = 0.0465
wR2 = 0.1275
2.003 and ¹1.768
R indices (all data)a)
¹3
Largest diff./e ¡ peak and hole
2
2 2
2 2 1/2
a) R1 = -««Fo« ¹ «Fc««/-«Fo«, wR2 = [(-w(Fo ¹ Fc ) /-w(Fo ) ]
.

160
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
Metal Complexes with New Tripodal Ligand
i-Pr
i-Pr
S
S
S
S
BuLi, TMEDA
PCl3
i-Pr
i-Pr
P
hexane, 50 °C
–40 °C ~ 25 °C
Li
S
i-Pr
1b: 96%
Scheme 1. Synthesis of ligand 1b.
dium(II) atom, and five-coordinate palladium(II) complexes are
very rare. There are only a few reports of X-ray structural
analysis of five-coordinate palladium(II) complexes bearing
bi-, tri-, and tetra dentate ligands.16 The formation of the five-
coordinate complexes 3a and 3b is very interesting. In addition,
the formation of the five-coordinate complexes 3a and 3b is in
sharp contrast to the case of the methyl derivative 1a, where
four-coordinate square-planar complexes, [PdCl2(1a)]¢dmf,
[Pd(1a)2](ClO4)2, and [Pd2Cl4(1a)], have been isolated.6,7
A
possible explanation for this difference is as follows. The steric
repulsion between bulkier isopropyl groups on the sulfur atoms
probably suppress the formation of a bis(chelate) complex,
[Pd(1b)2]2+. However, this explanation cannot be applied to the
suppression of the formation of a four-coordinate complex,
[PdCl2(1b)], where 1b acts as a bidentate ligand, since the
bulkier substituents on the sulfur atoms seem to favor the four-
coordinated structure, which is less congested than the five-
coordinate structure. It has been reported that the UV-vis
spectra of the palladium(II) complexes with 1a in solution fit
the trends of five-coordinate complexes.6 Therefore, in these
palladium(II) complexes with 1a and 1b, an equilibrium
between four- and five-coordinate complexes may exist, and
the complex with better crystallinity can be isolated. In the
isopropyl derivative, the five-coordinate complex 3b may have
better crystallinity, while, in the methyl derivative, the four-
coordinate complexes do.
Figure 1. ORTEP drawing of 1b with thermal ellipsoids
(50% probability).
Results and Discussion
Synthesis and Structure of Tris(2-isopropylthiophenyl)-
phosphine Ligand 1b. New tripodal tetradentate ligand 1b
was synthesized by the reaction of PCl3 with [2-(i-PrS)-
C6H4]Li,15 prepared from (i-PrS)C6H5,10 BuLi, and TMEDA
in hexane at 50 °C (Scheme 1). The structure of 1b was
1
determined by the H, 13C, and 31P NMR spectra, elemental
Reaction of 1b with [PtCl2(cod)] in CH2Cl2 at 25 °C for
48 h yielded the corresponding four-coordinate square-planar
complex 4 in good yield (Scheme 2). As for a platinum(II)
complex of the methyl-substituted ligand 1a, the isolation of a
bis(chelate) complex, [Pt(1a)2](ClO4)2, has been reported.7
This difference can be also explained by the steric repulsion
between bulkier isopropyl groups on the sulfur atoms. In
addition, anion-exchange reaction of platinum(II) complex 4
was attempted by the treatment of 4 with NaBF4 in C6H6 at
25 °C, however it unsuccessfully resulted in the quantitative
recovery of 4.
analysis, and X-ray crystallography. The X-ray structural
analysis of 1b showed that the three sulfur atoms situated in
the same side of the lone pair of the phosphorus (Figure 1).
This pre-organized structure suggests that 1b can behave as a
tetradentate ligand.
Synthesis of Group 10 Metal Complexes with Ligand 1b.
Ligand 1b reacted with NiCl2¢6H2O in refluxing CH2Cl2 in the
presence of NaBF4 for 72 h to afford a five-coordinate, cationic
complex 2 with trigonal-bipyramidal geometry as blue crystals
in 95% yield (Scheme 2). The formation of the five-coordinate
complex 2 is similar to the case of the use of methyl derivative
1a as a ligand.2,4,5 Reaction in the absence of NaBF4 resulted in
the quantitative recovery of ligand 1b.
1
The structures of complexes 2-4 were determined by H,
13C, and 31P NMR spectra, UV-vis spectra, and elemental
analyses. In addition, the structures of 2, 3b, and 4 in the
crystalline state were revealed by X-ray crystallography. The
details of the structures in the crystalline state and in solution
will be discussed in the following sections.
Reaction of 1b with [PdCl2(PhCN)2] in CH2Cl2 at 25 °C for
72 h gave the corresponding five-coordinate trigonal-bipyrami-
dal complex 3a in good yield (Scheme 2). In addition, anion-
¹
exchange reaction of 3a with BF4 was performed by the
Crystal Structures of Group 10 Metal Complexes. The
crystal structures of 2, 3b, and 4 were determined by X-ray
crystallography. The slow recrystallization of 3b from hexane/
CHCl3 gave two types of crystals, 3bi and 3bii. The ORTEP
drawings of 2, 3bi, 3bii, and 4 are shown in Figures 2-5,
treatment of 3a with NaBF4 in CH2Cl2 at 25 °C for 24 h to
afford the corresponding five-coordinate trigonal-bipyramidal
complex 3b in 90% yield (Scheme 2). Generally, palladium(II)
complexes possess square-planar geometry around the palla-

N. Takeda et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
161
+
+
Cl
Cl
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
S
S
S
S
S
S
Ni
P
Pd
P
–
–
BF
Cl
4
2: 95%
3a: 76%
(i)
(ii)
i-Pr
i-Pr
S
S
(iii)
P
S
i-Pr
1b
(iv)
+
Cl
Cl
i-Pr
i-Pr
i-Pr
i-Pr
S
S
Pt Cl
S
Pd
P
i-Pr
S
–
S
P
BF
4
S
i-Pr
4: 89%
3b: 90%
(i) NiCl2·6H2O, NaBF4, CH2Cl2, reflux, 72 h; (ii) [PdCl2(PhCN)2], CH2Cl2, 25 °C, 72 h; (iii)
NaBF4, CH2Cl2, 25 °C, 24 h; (iv) [PtCl2(cod)], CH2Cl2, 25 °C, 48 h.
Scheme 2. Synthesis of group 10 metal complexes with 1b.
Figure 2. ORTEP drawing of 2 with thermal ellipsoids
(50% probability).
Figure 3. ORTEP drawing of 3bi with thermal ellipsoids
(50% probability).
respectively, and selective bond lengths and angles of these
complexes are shown in Tables 3 and 4.
As shown in Figure 2, nickel(II) complex 2 possesses a
slightly distorted trigonal-bipyramidal geometry, where the
three S atoms are located in the equatorial positions and the P
and Cl atoms are located in the apical positions (P-Ni-Cl
178.60(3)°). The bond distances and angles around the
nickel(II) center in 2, except for the Ni-S3 bond distance, are
similar to those for the reported trigonal-bipyramidal nickel(II)
complex of the methyl-substituted ligand 1a, [NiCl(1a)]ClO4
(6).5 The Ni-S3 bond distance (2.3510(7) ¡) in 2 is slightly
longer than the other two Ni-S bonds (2.2678(7) and
2.2454(7) ¡), while the three Ni-S bond distances of the
methyl derivative 6 are similar values (2.269(6), 2.242(8), and

162
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
Metal Complexes with New Tripodal Ligand
Table 3. Selected Bond Lengths/¡ and Angles/° for 2, 3bi,
and 3bii
2 (M = Ni) 3bi (M = Pd) 3bii (M = Pd)
M-P
2.1108(7)
2.2678(7)
2.2454(7)
2.3510(7)
2.2437(7)
2.1787(16)
2.3818(16)
2.3437(17)
2.6515(16)
2.3782(16)
2.1700(11)
2.3893(12)
2.3685(12)
2.5840(11)
2.3768(11)
M-S1
M-S2
M-S3
M-Cl
P-M-Cl
178.60(3)
87.50(3)
87.23(3)
86.98(2)
92.10(3)
92.01(3)
94.42(2)
130.74(3)
119.03(3)
109.53(3)
174.12(6)
85.78(6)
87.89(6)
83.06(6)
94.23(6)
88.07(6)
102.56(6)
136.62(6)
115.72(6)
106.01(5)
179.54(4)
86.33(4)
86.05(4)
84.38(4)
93.57(4)
94.33(4)
95.22(4)
135.03(4)
116.59(4)
106.62(4)
P-M-S1
P-M-S2
P-M-S3
Cl-M-S1
Cl -M-S2
Cl -M-S3
S1-M-S2
S2-M-S3
S3-M-S1
Figure 4. ORTEP drawing of 3bii with thermal ellipsoids
(50% probability).
Table 4. Selected Bond Lengths/¡ and Angles/° for 4
Pt-P
2.2194(18)
2.3269(17)
2.3647(17)
2.2446(19)
3.6228(19)
P-Pt-S1
89.46(7)
92.45(7)
86.03(7)
92.20(6)
Pt-Cl1
Pt-Cl2
Pt-S1
Pt-S2
P-Pt-Cl1
S1-Pt-Cl2
Cl1-Pt-Cl2
addition, the S1-Pd-S2 bond angles (3bi: 136.62(6)°, 3bii:
135.03(4)°) are larger than the S2-Pd-S3 and S3-Pd-S1 bond
angles (3bi: 115.72(6) and 106.01(5)°, 3bii: 116.59(4) and
106.62(4)°, respectively). This elongation of the Pd-S3 bonds
with the expansion of the S1-Pd-S2 bond angle, that is, the
approach to four-coordinate square-planar structure from five-
coordinate trigonal-bipyramidal structure, is also probably due
to the reduction of the steric repulsion between the isopropyl
groups as in the case of nickel(II) complex 2. The Pd-Cl bond
lengths (3bi: 2.3782(16) ¡, 3bii: 2.3768(11) ¡) are slightly
longer than those of four-coordinate palladium(II) complexes
bearing phosphine and chloro ligands in the trans position to
each other, e.g., cis-[PdCl2{PPh2{2-[(MeOC10H7)S(O)]C6H4}-
¬2P,S}] (2.356(2) ¡)18 and cis-[PdCl2{2-Ph2P-2¤-MeS(1,1¤-
binaphthyl)-¬2P,S}] (2.350(2) ¡).19 The Pd-P bond lengths
(3bi: 2.1787(16) ¡, 3bii: 2.1700(11) ¡) are slightly shorter
than those of four-coordinate palladium(II) complexes
bearing phosphine and chloro ligands in the trans position
to each other, e.g., [PdCl2{PPh2{2-[(MeOC10H7)S]C6H4}}]
(2.229(2) ¡)18 and cis-[PdCl2{2-Ph2P-2¤-MeS(1,1¤-binaphthyl)-
¬2P,S}] (2.258(2) ¡).19 The shortness of the Pd-P bond lengths
can be explained by the coordination of three thioether moieties
tethered with the P atom. The slight elongation of the Pd-Cl
distances might be interpreted by the trans influence of the
phosphine ligand with short P-Pd bond length.
Figure 5. ORTEP drawing of 4 with thermal ellipsoids
(50% probability).
2.290(7) ¡).5 In addition, the S1-Ni-S2 bond angle
(130.74(3)°) in 2 is larger than the S2-Ni-S3 and S3-Ni-S1
bond angles (119.03(3) and 109.53(3)°, respectively). This
elongation of the Ni-S3 bonds together with the expansion of
the S1-Ni-S2 bond angle, that is, the approach to four-
coordinate square-planar structure from five-coordinate trigo-
nal-bipyramidal structure, is probably due to the reduction of
the steric repulsion between the bulkier isopropyl groups.
Figures 3 and 4 show the five-coordinate distorted trigonal-
bipyramidal structures of 3bi and 3bii, where the P and Cl
atoms are located in the apical positions (3bi: P-Pd-Cl
174.12(6)°, 3bii: P-Pd-Cl 179.54(4)°) and the Pd center is
out of the equatorial plane constructed by the three S atoms in
the direction of the Cl atom. The remarkable differences
¹
between 3bi and 3bii are the position of the BF4 anion relative
to the cationic part and the conformation of one isopropyl
group. The Pd-S1 and Pd-S2 bond lengths (3bi: 2.3818(16)
and 2.3437(17) ¡, 3bii: 2.3893(12) and 2.3685(12) ¡, respec-
tively) are slightly longer than those for the reported four-
coordinate palladium(II) complexes (2.290-2.302 ¡),17 and the
Pd-S3 bond lengths (3bi: 2.6515(16) ¡, 3bii: 2.5840(11) ¡)
are much longer than the Pd-S1 and Pd-S2 bond lengths. In
Figure 5 shows the four-coordinate square-planar struc-
ture of platinum(II) complex 4. The Pt-S1 and Pt-Cl1 bond
lengths (2.2446(19) and 2.3269(17) ¡, respectively) are nearly
within the range of the reported values for four-coordinated
platinum(II) complexes (Pt-S: 2.245-2.289 ¡, Pt-Cl: 2.297-
2.349 ¡),17 and the Pt-P and Pt-Cl2 bond lengths (2.2194(18)

N. Takeda et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
163
1
and 2.3647(17) ¡, respectively) are close to those of four-
coordinate platinum(II) complexes bearing phosphine and
chloro ligands in the trans position to each other, e.g.,
In the H and 13C NMR spectra of 2, 3a, and 3b, only one
peak for the methyl groups of the isopropyl groups was
observed. This suggests the rapid pyramidal inversion of the S
atoms (Scheme 3).
cis-[PtCl2{1-Ph2P-8-Ph2P(S)(naphthalene)-¬2P,S}]
(Pt-P:
2.2220(6) ¡ and Pt-Cl: 2.3694(6) ¡).17 The Pt-S2 distance
(3.623 ¡) is very near to the sum of van der Waals radii of Pt
(1.72 ¡) and S (1.80 ¡) atoms,20 therefore, very weak inter-
action between the Pt and S2 atoms may exist. The greater
length of the Pt-Cl2 bond (2.3647(17) ¡) compared with that
of the Pt-Cl1 bond (2.3269(17) ¡) is probably due to the larger
trans influence of Pt-P bonds compared with that of Pt-S
bonds.
Structures of Group 10 Metal Complexes in Solution.
Figure 6 shows the UV-vis spectra of 2-4. It is known that the
UV-vis spectra of five-coordinate group 10 metal complexes
show red shifts compared with those of the corresponding
square-planar complexes.2,3,6,21-23 The UV-vis spectra of 2,
3a, and 3b are similar to those of reported five-coordinate
complexes, [NiX(1a)]ClO4 (X = Cl, Br, I, and NCS)2 and
[PdCl{E[2-(Ph2E)C6H4]3}]X (E = P, X = Cl, BPh4;21 E = As,
X = ClO422), while the UV-vis spectrum of 4 is similar to
To clarify the detailed structure in solution, the effects of
temperature and concentration on the NMR spectra were
investigated. In the H NMR spectrum of palladium(II) com-
1
plex 3a at ¹40 °C, no change was observed in the number of
methyl signals. This result suggests the rapid pyramidal
inversion of the S atoms even at ¹40 °C. In addition, this
spectrum at ¹40 °C displayed the up-field shift of the aromatic
peak from 8.34 to 8.44 ppm at 20 °C to 8.20-8.34 ppm at
¹40 °C and down-field shift of the aromatic peak from 7.69 to
7.85 ppm at 20 °C to 7.77-7.94 ppm at ¹40 °C, while there is
little change in the chemical shift of other signals. Furthermore,
1
the concentration effects on the H NMR spectra of 3a was
observed; the aromatic proton signal observed at 8.34-8.44
ppm in a 60 mM CDCl3 solution of 3a shifted to 8.52 ppm in a
7.6 mM CDCl3 solution, and other peaks little changed in
solutions with various concentrations. These results may
suggest interaction between the cationic [PdCl(1b)]+ and the
¹
those of reported square-planar complexes, [PtCl2{PPh3¹n
-
counter anion Cl . A similar concentration effect was observed
[2-(Me2N)C6H4]n}] (n = 1, 2, and 3).23 These results strongly
suggest that nickel(II) and palladium(II) complexes 2, 3a, and
3b have five-coordinated trigonal-bipyramidal structures and
platinum(II) complex 4 has a square-planar structure in solution
as well as in the crystalline states.
in nickel(II) and palladium(II) complexes, 2 and 3b, therefore,
a similar interaction between the cationic parts, [NiCl(1b)]+
¹
and [PdCl(1b)]+, and the counter anion BF4 may exist.
1
The H NMR spectrum of the four-coordinate platinum(II)
complex 4 also showed only one peak for the methyl groups of
1
the isopropyl groups. This H NMR spectrum may seem to be
consistent with that of a five-coordinate trigonal-bipyramidal
complex, however the UV-vis spectrum of 4 is similar to
those of four-coordinate square-planar complexes as described
above. Therefore, it is concluded that platinum(II) complex 4
possesses four-coordinate square-planar geometry in a CDCl3
solution as in the crystalline state, and the coordinated and
uncoordinated sulfur atoms are rapidly exchanged to each other
(Scheme 4). The 1H NMR spectrum of 4 at ¹60 °C showed no
split in the methyl signal but the appearance of several small
peaks. In addition, in the 31P NMR spectrum at ¹60 °C, new
two small signals appeared, although no split in the main signal
was observed. These results indicate the rapid exchange of the
+
+
i-Pr
Cl
i-Pr
Cl
M
i-Pr
S
S
S
i-Pr
S
S
M
P
i-Pr
i-Pr
X–
X–
S
P
A
B
Scheme 3. Pyramidal inversion of S atoms.
Figure 6. UV-vis spectra of 2-4 in chloroform.
i-Pr
i-Pr
S3
i-Pr
Cl
Cl
Cl
Cl
Cl
P
Cl
P
S2
S1
Pt
Pt
Pt
i-Pr S1
P
i-Pr S2
i-Pr S3
S3
i-Pr
S1
i-Pr
S2
i-Pr
Scheme 4. Rapid exchange among thioether moieties.

164
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
Metal Complexes with New Tripodal Ligand
Res. 1997, 30, 9.
S atoms even at ¹60 °C and the existence of an equilibrium
among a small amount of isomers, the structures of which have
not been determined. These behaviors of platinum(II) complex
4 are very different from those of a square-planar complex
2
3
4
G. Dyer, D. W. Meek, Inorg. Chem. 1965, 4, 1398.
G. Dyer, D. W. Meek, Inorg. Chem. 1967, 6, 149.
J. R. Ferraro, D. W. Meek, E. C. Siwiec, A. Quattrochi,
1
J. Am. Chem. Soc. 1971, 93, 3862.
[PtCl2{PPh[2-MeSC6H4]2}] in solution, the H NMR spectrum
5
6
L. P. Haugen, R. Eisenberg, Inorg. Chem. 1969, 8, 1072.
G. Dyer, M. O. Workman, D. W. Meek, Inorg. Chem. 1967,
of which showed four methyl signals at 10 °C, indicating
slower pyramidal inversion of the sulfur atoms and slower
exchange between coordinated and uncoordinated sulfur atoms
6, 1404.
7
E. W. Abel, J. C. Dormer, D. Ellis, K. G. Orrell, V. Šik,
1
than the time scale of H NMR spectrometry.7 This difference
M. B. Hursthouse, M. A. Mazid, J. Chem. Soc., Dalton Trans.
1992, 1073.
may be ascribed to the isopropyl groups being larger than the
methyl groups, which leads to weaker coordination of sulfur to
the platinum.
8
W. S. Tsang, D. W. Meek, A. Wojcicki, Inorg. Chem. 1968,
7, 1263.
9
P. Suomalainen, R. Laitinen, S. Jääskeläinen, M. Haukka,
Conclusion
J. T. Pursiainen, T. A. Pakkanen, J. Mol. Catal. A: Chem. 2002,
179, 93.
10 M. Lamothe, M. B. Anderson, P. L. Fuchs, Synth. Commun.
1991, 21, 1675.
11 J. R. Doyle, P. E. Slade, H. B. Jonassen, Inorg. Synth. 1960,
6, 216.
A new tripodal tetradentate ligand 1b bearing one phosphine
and three thioether moieties was synthesized by the reaction of
[2-(i-PrS)C6H4]Li with PCl3 in good yield. Ligand 1b formed
1:1 complexes with group 10 metals, and their structures in
crystalline states and in solution were discussed.
12 J. X. McDermott, J. F. White, G. M. Whitesides, J. Am.
Chem. Soc. 1976, 98, 6521.
13 G. M. Sheldrick, SHELXS-97 and SHELXL-97, Program
for the Solution of Crystal Structures, University of Göttingen,
Germany, 1997.
14 A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C.
Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 1999, 32, 115.
15 W. Bauer, P. A. A. Klusener, S. Harder, J. A. Kanters,
A. J. M. Duisenberg, L. Brandsma, P. R. Schleyer, Organo-
metallics 1988, 7, 552.
16 a) J. M. Vila, M. T. Pereira, J. M. Ortigueira, J. J.
Fernández, A. Fernández, M. López-Torres, H. Adams, Organo-
metallics 1999, 18, 5484. b) M. Lousame, A. Fernández, M.
López-Torres, D. Vázquez-García, J. M. Vila, A. Suárez, J. M.
Ortigueira, J. J. Fernández, Eur. J. Inorg. Chem. 2000, 2055. c) M.
López-Torres, A. Fernández, J. J. Fernández, A. Suárez, M. T.
Pereira, J. M. Ortigueira, J. M. Vila, H. Adams, Inorg. Chem.
2001, 40, 4583. d) R. B. Bedford, M. Betham, C. P. Butts, S. J.
Coles, M. Cutajar, T. Gelbrich, M. B. Hursthouse, P. N. Scully, S.
Wimperis, Dalton Trans. 2007, 459. e) J. S. Ye, W. Chen, D.
Wang, Dalton Trans. 2008, 4015. f) L. Naya, D. Vázquez-García,
M. López-Torres, A. Fernández, J. M. Vila, N. Gómez-Blanco, J. J.
Fernández, J. Organomet. Chem. 2008, 693, 685.
17 A. G. Orpen, L. Brammer, F. H. Allen, O. Kennard, D. G.
Watson, R. Taylor, J. Chem. Soc., Dalton Trans. 1989, S1.
18 K. Horoi, Y. Suzuki, Y. Kaneko, F. Kato, I. Abe, R.
Kawagishi, Polyhedron 2000, 19, 525.
Nickel(II) and palladium(II) complexes, 2 and 3b, possess
distorted trigonal-bipyramidal geometry, and the distortion of
palladium(II) complex 3b is larger than that of nickel(II)
complex 2. Platinum(II) complex 4 possesses four-coordinate
square-planar structure. These results are consistent with the
tendency to form five-coordinate complex in the order of
NiII > PdII > PtII.24
The NMR experiments suggest the rapid pyramidal inver-
sion of the sulfur atom in 2, 3a, and 3b and the rapid exchange
among the coordinated and uncoordinated sulfur atoms in 4 in
solution. In addition, in five-coordinate nickel(II) and palla-
dium(II) complexes, 2, 3a, and 3b, the interaction between the
cationic and the anionic portions was suggested.
This work was partially supported by Grant-in-Aid for
Scientific Research (C) from Japan Society for the Promotion
of Science (JSPS). We are grateful to Professor Soichiro
Kyushin, Graduate School of Technology, Gunma University
for his kind permission to use his single-crystal X-ray
diffractometer. In addition, we thank Assistant Professor
Shinichi Kondo, Graduate School of Technology, Gunma
University and Assistant Professor Masaki Yamamura, Depart-
ment of Chemistry, Tsukuba University for valuable discus-
sions.
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