Synthesis, structure, and catalytic activity of bimetallic pt II-IrIII complexes bridged by cyclooctane- 1,2-dithiolato ligands

Article abstract of DOI:10.1002/ejic.200900958

Cationic Pt^IIIr^III heterobimetallic complexes bridged by cyclooctane-l.,2-dithiolato ligands [(PPh₃)₂Pt(μ ²-SRS)IrCl(η⁵Cp-*)[SbF₆] [R = cis-C₈H₁₄ (5), trans

Full text of DOI:10.1002/ejic.200900958

FULL PAPER
DOI: 10.1002/ejic.200900958
Synthesis, Structure, and Catalytic Activity of Bimetallic PtII–IrIII Complexes
Bridged by Cyclooctane-1,2-dithiolato Ligands
Norio Nakata,[a] Masahiro Sakashita,[a] Chizuru Komatsubara,[a] and Akihiko Ishii*[a]
Keywords: Heterometallic complexes / Platinum / Iridium / S ligands / Hydrosilylation
Cationic PtII–IrIII heterobimetallic complexes bridged by cy- ray crystallographic analysis of 5 revealed that the PtS2Ir core
clooctane-1,2-dithiolato ligands [(PPh3)2Pt(µ2-SRS)IrCl(η5-
Cp*)][SbF6] [R = cis-C8H14 (5), trans-C8H14 (6), Cp* = C5Me5]
were synthesized by reaction of (cyclooctane-1,2-dithiolato)-
PtII complexes [Pt(SRS)(PPh3)2] [R = cis-C8H14 (3), trans-
C8H14 (4)] with [IrCl(µ-Cl)(η5-Cp*)]2 in thf in the presence
of AgSbF6. The structures of complexes 5 and 6 were fully
characterized by their NMR spectroscopic data. Moreover, X-
exhibits a hinged arrangement, in which the cis-cyclooctane-
1,2-dithiolate acts as a bridging ligand between the platinum
and iridium metals. Complexes 5 and 6 served as a catalyst
in the hydrosilylation of terminal alkynes RЈCCH (RЈ = Ph,
Bu, CO2Me) with tertiary hydrosilanes such as Et3SiH and
Ph3SiH to afford selectively β-(Z)-vinylsilanes 8 in high
yields.
Introduction
Heterobimetallic complexes involving sulfur ligands are
of current interest because of their relevance in applications
as catalyst precursors in homogeneous catalytic processes
and as starting materials for clusters preparation.[1] While
many examples of heterobimetallic complexes with thiolato
bridging ligands (RS–) have been reported so far,[2] dithiol-
ato-bridged (–SRS–) heterobimetallic complexes have been
investigated for several cases of the early–late and late–late
types.[3,4] Among them, a number of complexes containing
group 8 and group 10 metals bridged by the dithiolato li-
gands have been described recently. Claver et al. described
the synthesis and X-ray determination of the first examples
of heterobimetallic PtII–RhI and PdII–RhI complexes (A)
with a bridging 1,2-ethanedithiolato ligand.[5] They have
also found that these bimetallic complexes served as catalyst
precursors for the hydroformylation of styrene.[6] In ad-
dition, half-sandwich heterobimetallic PtII–RhIII and PtII–
IrIII complexes (B) containing a 1,2-ethanedithiolato ligand
have also been prepared by Masdeu-Bultó and co-
workers.[7] Recently, Woollins et al. reported the synthesis
and characterization of heterobimetallic PtII–RhI, PtII–
RhIII, and PtII–IrIII complexes (C, D) containing a bridging
naphthalene-1,8-dithiolato ligand.[8] However, X-ray struc-
tural analysis and the reactivity of heterobimetallic dithiol-
ato-bridged Pt–Ir complexes has not been reported.
Meanwhile, the coordination chemistry of cycloalkane-
1,2-dithiolato ligands is quite rare relative to that of com-
plexes containing other bidentate dithiolato ligands such as
benzene-1,2-dithiolate or ethane-1,2-dithiolate. Recently, we
reported the preparation of novel cis- and trans-cyclo-
octane-1,2-dithiols.[9] In addition, we developed a large-
scale synthetic method for trans-cyclooctane-1,2-dithiol.[10,11]
In this paper, we present the synthesis and characterization
of (cyclooctane-1,2-dithiolato)platinum complexes cis-[Pt-
(SRS)(PPh3)2] [R = cis-C8H14, trans-C8H14] and cationic
PtII–IrIII heterobimetallic complexes bridged by cyclo-
octane-1,2-dithiolato ligands [(PPh3)2Pt(µ2-SRS)IrCl(η5-
Cp*)][SbF6] [R = cis-C8H14, trans-C8H14, Cp* = C5Me5].
We also describe the stereoselective hydrosilylation of ter-
minal alkynes catalyzed by these PtII–IrIII heterobimetallic
complexes.
[a] Department of Chemistry, Graduate School of Science and
Engineering, Saitama University
Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan
Fax: +81-48-858-3700
E-mail: ishiiaki@chem.saitama-u.ac.jp
Eur. J. Inorg. Chem. 2010, 447–453
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
447

N. Nakata, M. Sakashita, C. Komatsubara, A. Ishii
FULL PAPER
[2.308(4),
2.339(4) Å],[12]
[Pt(2,2Ј-S2-biphen)(PPh3)2]
Results and Discussion
[2.330(10), 2.368(10) Å],[14] and [Pt(1,8-S2-nap)(PMe3)2]
Synthesis and Structure of (Cyclooctane-1,2-dithiolato)PtII
Complexes
First, we prepared (cyclooctane-1,2-dithiolato)PtII com-
plexes cis-[Pt(SRS)(PPh3)2] [R = cis-C8H14 (3), trans-C8H14
(4)] as the starting materials. Thus, treatment of cis- or
trans-cyclooctane-1,2-dithiol (1, 2) with [PtCl2(Ph3P)2] in
the presence of an acid scavenger such as Et3N in CH2Cl2
at 0 °C formed efficiently the corresponding complexes 3
and 4, which were purified by washing with Et2O, in 90 and
84% yield, respectively (Scheme 1).
Figure 1. ORTEP drawing of (cis-cyclooctane-1,2-dithiolato)PtII
complex 3 with 30% thermal ellipsoids. A solvated CH2Cl2
molecule and hydrogen atoms are omitted for clarity.
Scheme 1. Synthesis of (cyclooctane-1,2-dithiolato)PtII complexes
3 and 4.
The molecular structures of 3 and 4 were fully deter-
mined by NMR spectroscopy and X-ray crystallography. In
the 1H NMR spectra, the equivalent methine protons in the
cyclooctane ring of 3 (δ = 3.38–3.52 ppm) and 4 (δ = 2.89–
2.90 ppm) are shifted upfield from those of starting materi-
als 1 (δ = 3.40–3.46 ppm) and 2 (δ = 3.09–3.11 ppm). The
31P{1H} NMR spectra of 3 and 4 showed single resonances
with 195Pt satellites at δ = 21.6 ppm (1JPt,P = 2863 Hz) and δ
= 21.4 ppm (1JPt,P = 2847 Hz), respectively. These coupling
constant values are quite similar to those of aliphatic cis-
(dithiolato)PtII complexes, [Pt(S2C7H8)(PPh3)2] (C7H8
5,6-cyclohepta-1,3-dienyl) (1JPt,P 2847 Hz)[12] and
[Pt(SCH2–1-Ad)2(PPh3)2] (1-Ad = 1-adamantyl) (1JPt,P
=
=
=
2827 Hz).[13] The crystal structures of complexes 3 and 4
are shown in Figures 1 and 2 and selected bond lengths and
angles are summarized in Table 1. X-ray structural analyses
revealed that the platinum centers of 3 and 4 have distorted
square-planar environments, and the dithiolato ligands che-
late to the platinum metals, forming twisted five-membered
rings. The cyclooctane rings in 3 and 4 adopt boat–boat
and crown conformations, respectively. The P1–Pt1–P2
angles of 3 and 4 are in the range of 96.73(3)–97.34(3)° and
somewhat deviated from the ideal 90°. A similar deviation,
attributed to steric repulsion between two PPh3 ligands, was
observed in previously investigated platinum(II) complexes,
[Pt(S2C7H8)(PPh3)2] [98.50(11)°],[12] [Pt(2,2Ј-S2-biphen)-
(PPh3)2] [97.21(12)°],[14] [Pt(SC6F4H)(PPh3)2][96.54(4)°],[15]
and [Pt(SC6F5)(PPh3)2] [96.31(7)°].[15] The S1–Pt1–S2
angles [3: 86.63(10)°; 4: 87.39(3)°] are close to those in the
ideal square-planar geometry. The Pt–S bond lengths [3:
2.3136(9), 2.309(5) Å; 4: 2.3025(10), 2.3185(10) Å] lie in a
narrow range and are similar to those in cyclic dithiolato
ligands in platinum complexes, [Pt(S2C7H8)(PPh3)2]
Figure 2. ORTEP drawing of (trans-cyclooctane-1,2-dithiolato)PtII
complex 4 with 30% thermal ellipsoids. A solvated CH2Cl2
molecule and hydrogen atoms are omitted for clarity.
Table 1. Selected bond lengths [Å] and bond angles [°] of complexes
3 and 4.
3
4
Pt1–S1
Pt1–S2
Pt1–P1
Pt1–P2
S1–C1
S2–C2
C1–C2
S1–Pt1–S2
P1–Pt1–P2
S1–Pt1–P2
S2–Pt1–P1
S1–Pt1–P1
S2–Pt1–P2
2.3136(9)
2.309(5)
2.2826(9)
2.2750(9)
1.810(6)
1.810(8)
1.521(9)
86.63(10)
97.34(3)
88.66(3)
87.34(10)
173.93(3)
174.90(9)
2.3025(10)
2.3185(10)
2.2888(10)
2.2748(10)
1.831(5)
1.824(4)
1.492(7)
87.39(3)
96.73(3)
88.36(3)
87.51(3)
174.86(3)
175.73(3)
448
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 447–453

Bimetallic PtII–IrIII Complexes Bridged by Cyclooctane-1,2-dithiolato Ligands
[2.320(1), 2.326(1) Å].[4b,16] The Pt–P bond lengths [3: bonds due to the bridging coordination of the IrIII metal.
2.2826(9), 2.2750(9) Å; 4: 2.2888(10), 2.2748(10) Å] are also An ORTEP drawing of complex 5 is depicted in Figure 3
comparable
to
the
corresponding
bonds
in and selected bond lengths and angles are given in Table 2.
[Pt(S2C7H8)(PPh3)2] [2.275(3), 2.296(3) Å][12] and [Pt(2,2Ј- The crystal structure of trans-derivative 6 was also revealed
S2-biphen)(PPh3)2] [2.283(6), 2.295(9) Å].[14]
by X-ray diffraction; however, we do not discuss it because
of insufficient refinement. The central IrS2Pt fragment of
5 exhibits a hinged arrangement, which has 125.2° of the
respective angle between the two neighboring coordination
planes. This angle (125.2°) is greater than those of the re-
lated PtII–RhIII bimetallic complexes, [(PPh3)2Pt(µ-
SCH2CH2S)RhCl(η5-C5H5)][BF4] (124.6°)[5] and [(PPh3)2-
Pt(µ-SCH2CH2S)Rh(cod)][ClO4] (111.27°),[7] probably due
to the steric influence between the cyclooctane ring and the
Cp* ligand on the iridium center. The iridium center of 5
adopts a distorted tetrahedral geometry with the centroid
of Cp* ring, the chlorido, and the 1,2-dithiolato sulfur
Synthesis and Structures of Cationic PtII–IrIII Bimetallic
Complexes Bridged by Cyclooctane-1,2-dithiolato Ligands
The synthetic approach for heterobimetallic complexes
comprising group 8 (Rh, Ir) and group 10 (Pd, Pt) metals
has been shown as the direct reaction of mononuclear di-
thiolato PdII or PtII complexes with cationic RhI or IrI com-
plexes.[5–8] In our investigation, we modified this synthetic
approach and examined the metal-exchange reactions of
cationic dithiolato PtII–AgI complexes with the dimeric IrIII
complex [IrCl(µ-Cl)(η5-Cp*)]2. Thus, complexes 3 and 4
were allowed to react with AgSbF6 (2 equiv.) in thf at room
temperature, followed by treatment with [IrCl(µ-Cl)(η5-
Cp*)]2 to give efficiently the corresponding cationic PtII–
IrIII heterobimetallic complexes [(PPh3)2Pt(µ2-SRS)IrCl(η5-
Cp*)][SbF6] [R = cis-C8H14 (5, 71%), trans-C8H14 (6, 61%)]
as orange crystals (Scheme 2).
The molecular structures of 5 and 6 were determined by
1H, 13C{1H}, and 31P{1H} NMR spectroscopy and X-ray
1
crystallographic analysis for 5. The H NMR spectra of 5
and 6 showed one singlet due to the Cp* moiety (5: δ =
1.68 ppm; 6: δ = 1.66 ppm) and a multiplet due to the meth-
ine protons in the bridging dithiolato ligand (5: δ = 3.00–
3.14 ppm; 6: δ = 2.82–3.05 ppm). The 31P{1H} NMR spec-
trum of 5 displayed one singlet with 195Pt satellites at δ =
14.5 ppm (1JPt,P = 3188 Hz). By contrast, the 31P{1H}
NMR spectrum of 6 exhibited two nonequivalent doublet
signals at δ = 11.6 and 14.4 ppm with similar 195Pt,31P cou-
pling constants: 3240 and 3269 Hz. These 195Pt,31P cou-
pling constant values are slightly larger than those of start-
ing complexes 3 and 4, which indicates that the Pt–P bonds
became stronger as a result of the weakening of the Pt–S ity.
Figure 3. ORTEP drawing of cationic PtII–IrIII heterobimetallic
complex 5 with 30% thermal ellipsoids. Two solvated thf molecules,
the [SbF6] counteranion, and hydrogen atoms are omitted for clar-
Scheme 2. Synthesis of cationic PtII–IrIII heterobimetallic complexes 5 and 6.
Eur. J. Inorg. Chem. 2010, 447–453
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
449

N. Nakata, M. Sakashita, C. Komatsubara, A. Ishii
FULL PAPER
atoms as the apexes. The platinum center of 5 also has a yield of the adducts, it did not affect the β-(Z) selectivity of
distorted square-planar environment (sum of the bond the reaction. Although the reactions of terminal alkynes 7
angles around platinum atom: 360.41°). The cyclooctane with Et3SiH afforded β-(Z) adducts 8 together with a small
ring of 5 takes a twist chair–chair conformation. The Pt–S amount of β-(E) isomers 9 (Table 3, Entries 1–4, and 9–12),
bond lengths [2.3669(13), 2.3832(12) Å] are slightly shorter this result was explained by the subsequent isomerization
than those of starting complex 3 [2.309(5), 2.3136(9) Å] and of kinetic β-(Z) product 8 under the conditions. On the
relatively similar to those observed in a half-sandwich other hand, the reactions with Ph3SiH efficiently produced
heterobimetallic Pt–Rh dithiolato-bridged complex only β-(Z) vinylsilanes 8 without the formation of β-(Z) 9
[(PPh3)2Pt(µ-SCH2CH2S)RhCl(η5-C5H5)][BF4] [2.376(3), or α isomers 10 (Table 3, Entries 5–8, and 13–16). This ten-
2.387(3) Å].[7] The Ir–S bond lengths [2.3638(13), dency was also observed in the hydrosilylation of terminal
[20]
2.4081(13) Å] are in reasonable agreement with those in alkynes by using [RhCl(µ-Cl)(η5-Cp*)]2
half-sandwich type Ir–thiolato complexes, [Ir(Cl)2(2- Cl)(η5-Cp*)]2.[21a]
SPyH)(η5-Cp*)] [2.357(9) Å][17] and [IrCl(η5-Cp*)(η2-2-
and [IrCl(µ-
Table 3. Catalytic hydrosilylation of terminal alkynes with Ir–Pt bi-
metallic complexes 5 and 6.
Ph2PC6H4S)] [2.380(2) Å].[18] The Pt–P bond lengths
[2.2892(13), 2.2800(13) Å] are close to those in complex 3
[2.283(6), 2.295(9) Å] and [(PPh3)2Pt(µ-SCH2CH2S)RhCl-
(η5-C5H5)][BF4] [2.282(2), 2.302(2) Å].[7]
Table 2. Selected bond lengths [Å] and bond angles [°] of complex
5.
Entry
Cat.
Alkyne 7
(RЈ)
Ratio[b] 8/9/
Yield
[%][c]
Ir1–S1
Ir1–S2
Ir1–Cl1
Pt1–S1
Pt1–S2
Pt1–P1
S1–Ir1–Cl1
S2–Ir1–Cl1
S1–Pt1–S2
P1–Pt1–P2
S1–Pt1–P2
2.3638(13)
2.4081(13)
2.4075(13)
2.3669(13)
2.3822(12)
2.2892(13)
89.71(4)
91.05(4)
73.68(4)
99.50(5)
94.94(4)
Pt1–P2
S1–C1
S2–C2
C1–C2
S1–Ir1–S2
2.2800(13)
1.849(5)
1.845(6)
1.562(7)
73.28(4)
Silane
10
1
5
5
5
5
5
5
5
5
6
6
6
6
6
6
6
6
Et3SiH
Et3SiH
Et3SiH
Et3SiH
Ph3SiH
Ph3SiH
Ph3SiH
Ph3SiH
Et3SiH
Et3SiH
Et3SiH
Et3SiH
Ph3SiH
Ph3SiH
Ph3SiH
Ph3SiH
Ph
Ph
Bu
CO2Me
Ph
Ph
Bu
CO2Me
Ph
Ph
Bu
CO2Me
Ph
Ph
Bu
CO2Me
94:6:0
96:4:0
91
97
82
67
91
96
78
53
90
91
78
72
84
80
71
55
2[a]
3
84:16:0
74:26:0
100:0:0
100:0:0
100:0:0
100:0:0
94:6:0
4
S2–Pt1–P1
S1–Pt1–P1
S2–Pt1–P2
Ir1–S1–Pt1
Ir1–S2–Pt1
92.29 (4)
163.75(4)
158.02(5)
91.44(5)
89.96(4)
5
6[a]
7
8
9
10[a]
11
12
13
14[a]
15
16
96:4:0
87:13:0
76:24:0
100:0:0
100:0:0
100:0:0
100:0:0
Catalytic Activities of Cationic PtII–IrIII Bimetallic
Complexes
Transition-metal-catalyzed hydrosilylation of alkynes is
still the most simple and straightforward method for the
preparation of vinylsilanes, which are very useful precursors
in organic synthesis.[19] The hydrosilylation of alkynes gen-
erally produces three regioisomers, that is, α, β-(E), and β-
(Z) isomers. As reported, Rh-[20] and Ir-catalyzed[21] hydro-
[a] Reactions were performed at room temperature for 30 min.
[b] The ratio of stereoisomers was determined by 1H NMR spec-
troscopy. [c] Isolated yields of mixtures of vinylsilanes after column
chromatography. All the vinylsilanes exhibited spectroscopic data
that was in agreement with the assigned structures.
A possible catalytic cycle for the hydrosilylation of alk-
silylation of alkynes leads to the formation of β-(E) adducts ynes catalyzed by 5 is illustrated in Scheme 3. The first
as the major product. To shed light on the catalytic activi- step involves the oxidative addition of the iridium center of
ties of the cationic PtII–IrIII heterobimetallic complexes complex 5 to the Si–H bond of tertiary silanes, yielding the
bridged by cyclooctane-1,2-dithiolato ligands, we examined cationic six-coordinate IrV species 11. Then, by the so-
the Ir-catalyzed hydrosilylation of terminal alkynes 7 by called modified Chalk–Harrod mechanism,[22] insertion of
using 1 mol-% of catalysts 5 and 6 under thf-reflux condi- terminal alkynes 7 into the Ir–Si bond of 11 occurs through
tions for 3 h. The results are summarized in Table 3. In all the coordination of alkynes 7 to the iridium center (12) to
cases, β-(Z)-vinylsilanes 8 were obtained in good yields with produce cationic vinyl–IrV complexes 13 or 15. On the basis
high selectivity. The catalytic activity of cis-derivative 5 is of the present Z selectivity of vinylsilanes obtained, the cat-
slightly higher than that of trans-derivative 6. The reactions ionic vinyl–IrV complex undergoing reductive elimination
of phenylacetylene with Et3SiH or Ph3SiH were complete in the final step should be (E)-vinyl–IrV species 15. Interme-
within 30 min even at room temperature (Table 3, Entries 2, diate 15 can be formed by the isomerization of initially
6, 10, and 14) to give 8 in high yields. Methyl propiolate formed (Z)-vinyl–IrV species 13 through η2-vinyl intermedi-
also underwent a similar reaction to give the corresponding ate 14 as proposed by Crabtree[23] or by the direct reaction
β-(Z) adducts in moderate yields (Table 3, Entries 4, 8, 12, of 11 and 7 as proposed by Leong.[21a] The driving force for
and 16). While the presence of an electron-withdrawing the former path is the riddance of steric repulsion between
substituent such as a methoxycarbonyl group reduced the the (Z)-vinyl moiety and the other ligands in 13.
450
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 447–453

Bimetallic PtII–IrIII Complexes Bridged by Cyclooctane-1,2-dithiolato Ligands
Scheme 3. A possible catalytic cycle for the hydrosilylation of terminal alkynes catalyzed by 5.
To explore the oxidative addition step in the mechanistic
pathway shown in Scheme 3, we examined the reaction of
Experimental Section
General: All experiments were performed under an argon atmo-
5 with an equimolar amount of Ph3SiH at room tempera-
sphere unless otherwise noted. Solvents were dried by standard
1
ture in thf. The H NMR spectrum of the reaction mixture
methods and freshly distilled prior to use. H, 13C, and 31P NMR
1
exhibited the characteristic broad signals at δ = –13.2 and
–13.1 ppm, which were assignable to the hydrido ligands
of six-coordinate IrV species 11 and its stereoisomer. These
chemical shifts are comparable to that of reported IrV com-
plex [IrCl(H)2(SiPh3)(η5-Cp*)] (δ = –11.6 ppm).[21a,24]
spectra were recorded with Bruker DPX-400 or DRX-400 (400,
100.7, and 162 MHz, respectively) spectrometers with the use of
CDCl3 as the solvent at room temperature. Elemental analyses were
carried out at the Molecular Analysis and Life Science Center of
Saitama University. High-resolution mass spectrometry (HRMS)
data were recorded by using a Hitachi-Hitec NanoFrontier eLD.
All melting points were determined with a Mel-Temp capillary tube
apparatus and are uncorrected.
Conclusions
(Cyclooctane-cis-1,2-dithiolato)bis(triphenylphosphane)platinum (3):
A mixture of [PtCl2(PPh3)2] (608.2 mg, 0.769 mmol) and cis-cyclo-
octane-1,2-dithiol (1) (134.8 mg, 0.764 mmol) in CH2Cl2 (10 mL)
was stirred at 0 °C for 5 min and then Et3N (0.3 mL, 2.166 mmol)
was added. The mixture was stirred at 0 °C for 2.5 h. After quench-
ing with dilute HCl and extraction with CH2Cl2, the organic layer
We have reported the systematic synthesis of (cyclo-
octane-1,2-dithiolato)platinum complexes cis-[Pt(SRS)-
(PPh3)2] [R = cis-C8H14 (3), trans-C8H14 (4)] and cationic
platinum–iridium heterobimetallic complexes bridged by
cyclooctane-1,2-dithiolato ligands [(PPh3)2Pt(µ2-SRS)IrCl- was dried with anhydrous Na2SO4. After removal of the solvent in
(η5-Cp*)][SbF6] [R = cis-C8H14 (5), trans-C8H14 (6)]. The
vacuo, the residual pale-yellow solid was purified by washing with
Et2O (ca. 10 mL) to give analytically pure [Pt(cis-S2C8H14)(PPh3)2]
molecular structures of complexes 3, 4, and 5 were revealed
by their spectroscopic data and by X-ray crystallography.
We also found that the hydrosilylation of terminal alkynes
was catalyzed by platinum–iridium heterobimetallic com-
plexes 5 and 6 to afford selectively β-(Z) vinylsilanes 8 in
good yields. Further investigations on the preparations and
catalytic activities of the novel Pt–Rh and Pt–Ir heterobi-
metallic complexes bridged by cyclooctane-1,2-dithiolato li-
gands are underway.
(3; 616.2 mg, 90%) as pale-yellow crystals. M.p. 239–240 °C (de-
comp.). 1H NMR (400 MHz, CDCl3): δ = 1.40–1.65 (m, 8 H), 1.77–
1.82 (m, 2 H), 2.10–2.17 (m, 2 H), 3.38–3.52 (m, 2 H), 7.11–7.15
(m, 12 H), 7.23–7.26 (m, 6 H), 7.42–7.47 (m, 12 H) ppm. 13C NMR
(100.6 MHz, CDCl3): δ = 26.6 (CH2), 28.7 (CH2), 32.5 (CH2), 54.8
2
3
(CH), 127.8 (t, JP,C = 5.7 Hz), 130.0 (s), 134.9 (t, JP,C = 5.1 Hz)
ppm. 31P NMR (162 MHz, CDCl3): δ = 21.6 (s, JPt,P = 2863 Hz)
1
ppm. C43H38P2PtS2 (875.93): calcd. C 55.21, H 4.74; found C 55.08,
H 4.68.
Eur. J. Inorg. Chem. 2010, 447–453
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
451

N. Nakata, M. Sakashita, C. Komatsubara, A. Ishii
FULL PAPER
(Cyclooctane-trans-1,2-dithiolato)bis(triphenylphosphane)platinum
(4): A mixture of [PtCl2(PPh3)2] (457.6 mg, 0.578 mmol) and trans-
cyclooctane-1,2-dithiol (2; 101.9 mg, 0.578 mmol) in CH2Cl2
(10 mL) was stirred at 0 °C for 5 min and then Et3N (0.3 mL,
2.166 mmol) was added. The mixture was stirred at 0 °C for 2.5 h.
After quenching with dilute HCl and extraction with CH2Cl2, the
organic layer was dried with anhydrous Na2SO4. After removal of
the solvent in vacuo, the residual pale-yellow solid was purified by
washing with Et2O (ca. 10 mL) to give analytically pure [Pt(trans-
S2C8H14)(PPh3)2] (4; 431.5 mg, 84%) as pale-yellow crystals. M.p.
277–279 °C (decomp.). 1H NMR (400 MHz, CDCl3): δ = 1.37–1.64
(m, 8 H), 1.71–1.79 (m, 2 H), 1.98–2.05 (m, 2 H), 2.89–2.90 (m, 2
[(PPh3)2Pt(µ-S,S-trans-C8H14)IrCl(η5-C5Me5)][SbF6] (6): A solu-
tion of AgSbF6 (52.2 mg, 0.152 mmol) in thf (5 mL) was added to
a suspension of 4 (136.6 mg, 0.152 mmol) in thf (5 mL). The mix-
ture was stirred at room temperature for 10 min and then a solution
of [IrCl(µ-Cl)(η5-Cp*)]2 (60.5 mg, 0.076 mmol) in thf (5 mL) was
added. The color of the solution changed to yellow from colorless.
The silver chloride salts formed were removed by filtration through
a pad of Celite and rinsed with hexane. After removal of the solvent
in vacuo, the residual yellow solid was purified by washing with
hexane (ca. 5ϫ3 mL) to give analytically pure complex
6
(141.4 mg, 61%) as yellow crystals. M.p. 200–201 °C (decomp.). 1H
NMR (400 MHz, CDCl3): δ = 1.06–1.39 (m, 8 H), 1.66 (m, 15 H),
H), 7.11–7.14 (m, 12 H), 7.23–7.26 (m, 6 H), 7.43–7.47 (m, 12 H) 1.82–1.86 (m, 2 H), 1.97–1.99 (m, 2 H), 2.82–3.05 (m, 2 H), 7.21–
ppm. 13C NMR (100.6 MHz, CDCl3): δ = 26.1 (CH2), 26.4 (CH2),
33.8 (CH2), 56.0 (CH), 127.4 (t, 2JP,C = 5.9 Hz), 129.9 (s), 134.9 (t,
3JP,C = 5.1 Hz) ppm. 31P NMR (162 MHz, CDCl3): δ = 21.4 (s,
1JPt,P = 2847 Hz) ppm. C43H38P2PtS2 (875.93): calcd. C 55.21, H
4.74; found C 55.38, H 4.62.
7.34 (m, 18 H), 7.38–7.47 (m, 12 H) ppm. 13C NMR (100.6 MHz,
CDCl3): δ = 9.5 (CH3), 23.9 (CH2), 24.3 (CH2), 25.7 (CH2), 26.2
(CH2), 35.6 (CH2), 38.8 (CH2), 62.6 (CH), 23.8 (CH), 90.9 (C),
128.4 (d, 2JP,C = 11.1 Hz), 128.5 (d, 1JP,C = 57.4 Hz), 129.3 (d, 1JP,C
4
4
= 59.4 Hz), 131.0 (d, JP,C = 1.0 Hz), 131.1 (d, JP,C = 1.0 Hz),
3
3
133.7 (d, JP,C = 11.1 Hz), 134.1 (d, JP,C = 10.1 Hz) ppm. 31P
[(PPh3)2Pt(µ-S,S-cis-C8H14)IrCl(η5-C5Me5)][SbF6] (5): A solution
of AgSbF6 (21.1 mg, 0.064 mmol) in thf (5 mL) was added to a
suspension of 3 (50.9 mg, 0.057 mmol) in thf (7 mL). The mixture
was stirred at room temperature for 10 min, and then a solution of
[IrCl(µ-Cl)(η5-Cp*)]2 (23.1 mg, 0.029 mmol) in thf (7 mL) was
added. The color of the solution changed to yellow from colorless.
The silver chloride salts formed were removed by filtration through
a pad of Celite and rinsed with hexane. After removal of the solvent
in vacuo, the residual yellow solid was purified by washing with
hexane (ca. 5ϫ3 mL) to give analytically pure complex 5 (61.4 mg,
71%) as yellow crystals. M.p. 198–200 °C (decomp.). 1H NMR
(400 MHz, CDCl3): δ = 1.09–1.56 (m, 12 H), 1.68 (s, 15 H), 3.00–
3.14 (m, 2 H), 7.24–7.28 (m, 12 H), 7.32–7.42 (m, 18 H) ppm. 13C
NMR (100.6 MHz, CDCl3): δ = 8.7 (CH3), 25.4 (CH2), 30.8 (CH2),
2
1
NMR (162 MHz, CDCl3): δ = 11.6 (d, JP,P = 16.2 Hz, JPt,P
3240 Hz), 14.4 (d, JP,P = 16.2 Hz, JPt,P = 3269 Hz) ppm. HRMS:
calcd. for C54H59ClIrP2PtS2 [M
1257.2489.
=
2
1
–
SbF6]+ 1257.2494; found
General Protocol for the Catalytic Hydrosilylation of Terminal Al-
kynes: The hydrosilylation of terminal alkynes with Et3SiH or
Ph3SiH was performed by using 1 mol-% of Pt–Ir complexes 5 and
6 in thf. The mixture was stirred under reflux for 3 h, and the sol-
vent was removed under reduced pressure. The residue was purified
by silica-gel column chromatography (hexane/CH2Cl2, 4:1). The
relative proportion of products was determined by careful integra-
tion of the 1H NMR spectrum. The assignments for the β-(Z), and
β-(E)-vinylsilanes were based upon spectroscopic comparison with
literature.[21a,25]
2
32.4 (CH2), 64.5 (CH), 90.5 (C), 128.4 (t, JP,C = 6.0 Hz), 129.3 (d,
1JP,C = 59.4 Hz), 131.2 (s), 134.4 (t, 3JP,C = 5.0 Hz) ppm. 31P NMR
X-ray Crystallographic Studies: Pale-yellow single crystals of 3 and
4 were grown by the slow evaporation of saturated CH2Cl2 and
hexane solutions, respectively, and yellow single crystals of 5 were
grown by the slow evaporation of its saturated thf and hexane solu-
1
(162 MHz, CDCl3): δ = 14.5 (s, JPt,P = 3188 Hz) ppm. HRMS:
calcd. for C54H59ClIrP2PtS2 [M
1257.2489.
–
SbF6]+ 1257.2494; found
Table 4. Crystallographic data and details of refinement for 3, 4, and 5.
3
4
5
Formula
Formula weight
Color
Crystal size [mm]
Temperature [K]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C45H46Cl2P2PtS2
978.87
pale yellow
0.36ϫ0.23ϫ0.21
103
C45H46Cl2P2PtS2
978.87
pale yellow
0.42ϫ0.40ϫ0.32
103
C62H75ClF6IrO2P2PtS2Sb
1636.77
yellow
0.24ϫ0.20ϫ0.11
103
orthorhombic
Pbca
16.7715(8)
21.4419(10)
34.3421(17)
90
triclinic
triclinic
¯
¯
P1
P1
11.3697(4)
14.8444(6)
14.8930(6)
60.6520(10)
68.6770(10)
86.1650(10)
2021.73(14)
2
11.3832(10)
14.7997(14)
14.8307(14)
61.780(2)
69.821(2)
73.570(2)
2044.6(3)
2
90
90
γ [°]
V [Å3]
12349.9(10)
8
Z
Dcalcd. [gcm–3]
No. of unique data
No. of parameters
No. of restraints
R1 [IϾ2σ(I)]
wR2 (all data)
GOF
1.608
8769
579
29
0.0313
0.0823
1.019
1.590
7579
497
0
0.0295
0.0756
1.034
1.761
11478
708
0
0.0333
0.0820
1.031
452
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 447–453

Bimetallic PtII–IrIII Complexes Bridged by Cyclooctane-1,2-dithiolato Ligands
win, J. D. Woollins, Eur. J. Inorg. Chem. 2007, 247–253; m) J. L.
tion in a Schlenk tube. The intensity data were collected at 103 K
for 3–5 with a Bruker AXS SMART diffractometer by employing
graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å). The
determination of crystal class and unit-cell parameters was carried
out by the SMART program package. The raw frame data were
processed by using SAINT and SADABS to yield the reflection
data file.[26] The structures were solved by direct methods and re-
fined by full-matrix least-squares procedures on F2 for all reflec-
tions (SHELX-97).[27] The hydrogen atoms were placed at the cal-
culated positions and were included in the structure calculation
without further refinement of the parameters. Crystal data, data
collection, and processing parameters for complexes 3–5 are sum-
marized in Table 4. CCDC-743418 (for 3), -743419 (for 4), and
-743420 (for 5) contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Hess, H. L. Conder, K. N. Green, M. Y. Daresbourg, Inorg.
Chem. 2008, 47, 2056–2063; n) J. Vicente, P. González-Herrero,
Y. G a r c ía-Sánchez, D. Bautista, Inorg. Chem. 2008, 47, 10662–
10673.
[5] J. Forniés-Cámer, A. M. Masdeu-Bultó, C. Claver, C. J. Cardin,
Inorg. Chem. 1998, 37, 2626–2632.
[6] J. Forniés-Cámer, A. M. Masdeu-Bultó, C. Claver, C. Tejel,
M. A. Ciriano, C. J. Cardin, Organometallics 2002, 21, 2609–
2618.
[7] J. Forniés-Cámer, C. Claver, A. M. Masdeu-Bultó, C. J. Cardin,
J. Organomet. Chem. 2002, 662, 188–191.
[8] S. M. Aucott, D. Duerden, Y. Li, A. M. Z. Slawin, J. D. Wool-
lins, Chem. Eur. J. 2006, 12, 5495–5504.
[9] A. Ishii, M. Suzuki, T. Sone, N. Nakata, Phosphorus Sulfur
Silicon Relat. Elem. 2009, 184, 1184–1205.
[10] A. Ishii, A. Ono, N. Nakata, J. Sulfur Chem. 2009, 30, 236–
244.
[11] For a recent application of trans-cyclooctane-1,2-dithiol, see:
A. Ishii, T. Toda, N. Nakata, T. Matsuo, J. Am. Chem. Soc.
2009, 131, 13566–13567.
[12] A. Ishii, S. Kashiura, Y. Hayashi, W. Weigand, Chem. Eur. J.
2007, 13, 4326–4333.
Acknowledgments
[13] N. Nakata, S. Yamamoto, W. Hashima, A. Ishii, Chem. Lett.
2009, 38, 400–401.
[14] S. M. Aucott, P. Kilian, S. D. Robertson, A. M. Z. Slawin, J. D.
Woollins, Chem. Eur. J. 2006, 12, 895–902.
This work was supported by the Ministry of Education, Science,
Sports, and Culture of Japan through a Grant-in-Aid for Scientific
Research (Nos. 18750026, 19027014, and 20036013).
[15] F. Estudiante-Negrete, R. Redón, S. Hernández-Ortega, R. A.
Toscano, D. Morales-Morales, Inorg. Chim. Acta 2007, 360,
1651–1660.
[16] S. M. Aucott, H. L. Milton, S. D. Robertson, A. M. Z. Slawin,
G. D. Walker, J. D. Woollins, Chem. Eur. J. 2004, 10, 1666–
1676.
[17] Y.-F. Han, Y.-B. Huang, Y.-J. Lin, G.-X. Jin, Organometallics
2008, 27, 961–966.
[18] M. Gorol, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt, Eur.
J. Inorg. Chem. 2005, 4840–4844.
[19] B. Marciniec in Comprehensive Handbook on Hydrosilylation,
Pergamon, Oxford, 1992, p. 130.
[20] J. W. Faller, D. G. D’Alliessi, Organometallics 2002, 21, 1743–
1746.
[21] For recent examples of highly β-(Z)-selective, Ir-catalyzed
hydrosilylations, see: a) V. S. Sridevi, W. Y. Fan, W. K. Leong,
Organometallics 2007, 26, 1157–1160; b) Y. Miyake, E. Iso-
mura, M. Iyoda, Chem. Lett. 2006, 35, 836–837; c) M. Viciano,
E. Mas-Marza, M. Sanau, E. Peris, Organometallics 2006, 25,
3063–3069; d) E. Mas-Marza, M. Sanau, E. Peris, Organome-
tallics 2006, 25, 3713–3720; e) E. Mas-Marza, M. Sanau, E.
Peris, Inorg. Chem. 2005, 44, 9961–9967.
[1] For general reviews, see: a) P. Braunstein, J. Rose in Compre-
hensive Organometallic Chemistry II (Eds.: G. Wilkinson,
F. G. A. Stone, E. W. Abel), Pergamon, Oxford, 1995, vol. 10,
p. 351; b) R. D. Adams, M. J. Chetcuti in Comprehensive Orga-
nometallic Chemistry II (Eds.: G. Wilkinson, F. G. A. Stone,
E. W. Abel), Pergamon, Oxford, 1995, vol. 10, p. 1, p. 23; c)
for the chemistry of heteronuclear clusters and multimetallic
catalysts, see: R. D. Adams, W. A. Herrmann, Polyhedron 1988,
7, 2251–2253; d) N. Wheatley, P. Kalck, Chem. Rev. 1999, 99,
3379–3403.
[2] a) D. W. Stephan, Coord. Chem. Rev. 1989, 95, 41–107; b)
M. D. Janssen, D. M. Grove, G. Van Koten, Prog. Inorg. Chem.
1997, 46, 97–149; c) M. Y. Darensbourg, M. Pala, S. A. Houlis-
ton, K. P. Kidwell, D. Spencer, S. S. Chojnacki, J. H. Reibensp-
ies, Inorg. Chem. 1992, 31, 1487–1493; d) V. W.-W. Yam, K. M.-
C. Wong, K.-K. Cheung, Organometallics 1997, 16, 1729–1734;
e) R. Rousseau, D. W. Stephan, Organometallics 1991, 10,
3399–3403.
[3] T. T. Nadasdi, D. W. Stephan, Inorg. Chem. 1994, 33, 1532–
1538 and references cited therein.
[4] a) J. Vicente, M. T. Chicote, S. Huertas, D. Bautista, P. G.
Jones, A. K. Fischer, Inorg. Chem. 2001, 40, 2051–2057; b) J.
Vicente, M. T. Chicote, S. Huertas, P. G. Jones, A. K. Fischer,
Inorg. Chem. 2001, 40, 6193–6200; c) J. Forniés-Cámer, A. M.
Masdeu-Bultó, C. Claver, Inorg. Chem. Commun. 2002, 5, 351–
354; d) R. Y. C. Shin, J. J. Vittal, Z.-Y. Zhou, L. L. Koh, L. Y.
[22] a) J. F. Harrod, A. J. Chalk, I. Wender, P. Pino in Organic Syn-
thesis via Metal Carbonyls, Wiley, New York, 1977, vol. 2, p.
673; b) M. A. Schroeder, M. S. Wrighton, J. Organomet. Chem.
1977, 128, 345–358.
[23] R. H. Crabtree, New J. Chem. 2003, 27, 771–772.
Goh, Inorg. Chim. Acta 2003, 352, 220–228; e) S. M. Aucott, [24] M.-J. Fernandez, P. M. Maitlis, J. Chem. Soc., Dalton Trans.
H. L. Milton, S. D. Robertson, A. M. Z. Slawin, J. D. Woollins,
Dalton Trans. 2004, 3347–3352; f) R. Y. C. Shin, G. K. Tan,
L. L. Koh, L. Y. Goh, R. D. Webster, Organometallics 2004, 23,
6108–6115; g) Y.-D. Chen, L.-Y. Zhang, L.-X. Shi, Z.-N. Chen,
Inorg. Chem. 2004, 43, 7493–7501; h) R. Y. C. Shin, M. E. Teo,
G. K. Tan, L. L. Koh, J. J. Vittal, L. Y. Goh, K. S. Murray, B.
Moubaraki, X.-Y. Zhou, Organometallics 2005, 24, 4265–6273;
i) S. Takemoto, D. Shimadzu, K. Kamikawa, H. Matsuzaka,
R. Nomura, Organometallics 2006, 25, 982–988; j) J. Vicente, P.
González-Herrero, M. Pérez-Cadenas, P. G. Jones, D. Bautista,
Inorg. Chem. 2007, 46, 4718–4732; k) R. Y. C. Shin, V. W. L.
Ng, L. L. Koh, G. K. Tan, L. Y. Goh, R. D. Webster, Organo-
metallics 2007, 26, 4555–4561; l) S. D. Robertson, A. M. Z. Sla-
1984, 2063–2066.
[25] a) E. Lukevics, R. Ya. Sturkovich, O. A. Pudova, J. Organomet.
Chem. 1985, 292, 151–158; b) E. Lukevics, V. V. Dirnens, Y. S.
Goldberg, E. E. Liepinsh, J. Organomet. Chem. 1986, 316, 249–
254.
[26] G. M. Sheldrick, SADABS: Program for Empirical Absorption
Correction of Area Detector Data, University of Göttingen,
Göttingen, Germany, 1996.
[27] G. M. Sheldrick, SHELXTL 5.10 for Windows NT: Structure
Determination Software Programs, Bruker Analytical X-ray
Systems, Inc., Madison, WI, 1997.
Received: September 25, 2009
Published Online: December 8, 2009
Eur. J. Inorg. Chem. 2010, 447–453
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
453