Platinum dithiolene complexes of π-coordinating and π-interacting η4-cyclobutadiene ligands

Article abstract of DOI:10.1021/om900222s

Five new organometallic platinum dithiolene complexes of the η⁴-cyclobutadiene ligand [(η⁴-C₄Me ₄)Pt(dithiolene)] (dithiolene = mnt (2), dcmedt (3), tdt (4), dddt (5), dmit (6)) and one platinum diselenolene complex, [(η⁴-C ₄Me₄)Pt(dsit)] (7), were prepared from [(η⁴-C₄Me₄)Pt(Cl)(w-Cl)]₂ (1) and Na₂(mnt), O=C(dcmedt), H₂tdt, O=C(dddt), (NBu ₄)₂[Zn(dmit)₂], or (NEt₄) ₂[Zn(dsit)₂], respectively. The (η⁴-C ₄Me₄)Pt complexes 2-7 were characterized by NMR, UV-vis spectra, and CV. Those ¹H and ¹³C NMR spectra showed ¹⁹⁵Pt satellite coupling at the C₄Me₄ (J _pt-H = 13-15 Hz), at the C₄Me₄ (J _Pt-c = ca. 100 Hz), and at the dithiolene carbons. The complexes having an electron-rich dichalcogenolene ligand (5-7) resulted in lower energy electronic absorption compared with the electron-poor series 2-4. The η⁴-C₄Me₄ ligand was replaced by the nucleophilic substitution of bis(diphenylphosphino)ethane (DPPE) to form the square-planar [Pt(dithiolene)(dppe)] complex. 2, 3, and 5-7 were structurally determined by X-ray diffraction studies. All the molecules were monomeric, had two-legged piano-stool geometries, and were formal 16-electron complexes with the Pt^II (d⁸) center. The crystal structure of 2 showed an inversion-centered dyad. 5 had η⁴-C₄Me₄- ... -dithiolene plane-to-plane interaction in the crystal to form a zigzag chain. 6 and 7 were isostructural to each other and had intermolecular interactions through η⁴-C₄Me₄- ... -trithiocarbonate contacts to form a zigzag chain. The η⁴-C ₄Me₄ group behaves as a π-coordinating ligand and a π-interacting ligand as well. Dithiolene and diselenolene ligands used in this work were as follows: mnt = maleonitrile-1,2-dithiolate, dcmedt = 1,2-dimethoxycarbonylethylene-1,2-dithiolate, tdt = toluene-3,4-dithiolate, dddt = 5,6-dihydrol,4-dithiine-2,3-dithiolate, dmit = 1,3-dithiol-2-thione-4,5- dithiolate, and dsit = 1,3-dithiol-2-thione-4,5diselenolate.

Full text of DOI:10.1021/om900222s

3776 Organometallics 2009, 28, 3776–3784
DOI: 10.1021/om900222s
Platinum Dithiolene Complexes of π-Coordinating and π-Interacting
η4-Cyclobutadiene Ligands
Mitsushiro Nomura,*,† Takashi Fujii, and Masatsugu Kajitani*
Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1,
Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan. †Current address: Condensed Molecular Materials Laboratory,
RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan. E-mail: mitsushiro@riken.jp (M.N.)
Received March 24, 2009
Five new organometallic platinum dithiolene complexes of the η4-cyclobutadiene ligand
[(η4-C4Me4)Pt(dithiolene)] (dithiolene = mnt (2), dcmedt (3), tdt (4), dddt (5), dmit (6)) and one
platinum diselenolene complex, [(η4-C4Me4)Pt(dsit)] (7), were prepared from [(η4-C4Me4)Pt(Cl)-
(μ-Cl)]2 (1) and Na2(mnt), OdC(dcmedt), H2tdt, OdC(dddt), (NBu4)2[Zn(dmit)2], or (NEt4)2-
[Zn(dsit)2], respectively. The (η4-C4Me4)Pt complexes 2-7 were characterized by NMR, UV-vis
spectra, and CV. Those 1H and 13C NMR spectra showed 195Pt satellite coupling at the C4Me4 (JPt-H
=
13-15 Hz), at the C4Me4 (JPt-C = ca. 100 Hz), and at the dithiolene carbons. The complexes
having an electron-rich dichalcogenolene ligand (5-7) resulted in lower energy electronic absorption
compared with the electron-poor series 2-4. The η4-C4Me4 ligand was replaced by the nucleophilic
substitution of bis(diphenylphosphino)ethane (DPPE) to form the square-planar [Pt(dithiolene)(dppe)]
complex. 2, 3, and 5-7 were structurally determined by X-ray diffraction studies. All the molecules were
monomeric, had two-legged piano-stool geometries, and were formal 16-electron complexes with the PtII
(d8) center. The crystal structure of 2 showed an inversion-centered dyad. 5 had η4-C4Me4 dithiolene
3 3 3
plane-to-plane interaction in the crystal to form a zigzag chain. 6 and 7 were isostructural to each other
and had intermolecular interactions through η4-C4Me4 trithiocarbonate contacts to form a zigzag
3 3 3
chain. The η4-C4Me4 group behaves as a π-coordinating ligand and a π-interacting ligand as well.
Dithiolene and diselenolene ligands used in this work were as follows: mnt=maleonitrile-1,2-dithiolate,
dcmedt=1,2-dimethoxycarbonylethylene-1,2-dithiolate, tdt = toluene-3,4-dithiolate, dddt = 5,6-dihydro-
1,4-dithiine-2,3-dithiolate, dmit = 1,3-dithiol-2-thione-4,5-dithiolate, and dsit = 1,3-dithiol-2-thione-4,5-
diselenolate.
Introduction
based magnetic interaction,4 π-electron-induced electrical
conductivity,5 thermally driven valence tautomerism due to
the M/L-CT,6 photoexcited charge transfer due to the
π-electron,7 new olefin binding reactions derived from the
low-energy LUMO,8 and dithiolene-based “noninnocent
behavior”.9 Especially, homoleptic dithiolene complexes
such as square-planar bisdithiolene complexes and trigonal
prismatic trisdithiolene complexes,10 which include dithiolene
ligands only, exhibit a well-delocalized π-electron system.
Metal dithiolene complexes have an interesting π-electron
system because of π-electron delocalization for the low-
energy HOMO-LUMO gap,1 (4n+2)π-conjugation for
::
aromaticity (the Huckel’s rule),2 three-dimensional π-elec-
tron delocalization (nonplanar aromaticity),3 π-electron-
*Corresponding authors. E-mail: m-nomura@sophia.ac.jp (M.N.);
kajita-m@sophia.ac.jp (M.K.).
(1) (a) Kobayashi, A.; Sasa, M.; Suzuki, W.; Fujiwara, E.; Tanaka,
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r
2009 American Chemical Society
pubs.acs.org/Organometallics
Published on Web 05/28/2009

Article
Organometallics, Vol. 28, No. 13, 2009 3777
Recently, novel tetrakisdithiolene complexes of uranium and
cerium have been reported as well.11
Chart 1. 16-Electron Organometallic Dithiolene Complexes
with π-Coordinating Organic Ligand
In addition, heteroleptic dithiolene complexes, which have
a dithiolene ligand and some other ligands, are also attra-
ctive compounds. Especially, photophysical and optical
studies have been extensively investigated. Eisenberg et al.
reported the photoluminescence of [Pt(dithiolene)(N N)]
(N N=2,20-bipyridines, 1,10-phenanthrolines) and proved
the nature of the photoexcited state in 1990s.12 The
[Pt(dithiolene)(N N)] complex with a TiO2 system can be a
photocatalyst to generate molecular hydrogen from water,13
can also be one component of a dye-sensitized solar cell,14
and can exhibit nonlinear optical properties (NLO).15
Recently, Noh et al. reported [Pt(dithiolene)(P P)] (P P =
diphosphines) and their redox and photoluminescent prop-
erties.16 Furthermore, some conducting molecules have been
reported in the heteroleptic dithiolene complexes. The
partially oxidized [M(dithiolene)(C N)] (M = Au17 and Pt,18
C N = 2-phenylpyridine) complexes show electrical con-
ductivities.
On the other hand, organometallic dithiolene complexes
having η5-cyclopentadienyl (Cp) and η6-arene (η6-C6R6)
ligands are another category of dithiolene complexes.
Among them, the Cp/dithiolene complexes are further clas-
sified into four main categories:19 Cp/dithiolene ratio 2:1
complexes of general formula [Cp2M(dithiolene)]0,+1 (M =
group 4-6 metals), Cp/dithiolene ratio 1:2 complexes [CpM
(dithiolene)2]-1,0 (M = group 4-7 metals), Cp/dithiolene
ratio 1:1 complexes [CpM(dithiolene)] (M = group 9 and 10
metals, Chart 1), and bimetallic 1:1 complexes [CpM(dithio-
lene)]2 (M = group 5, 6, and 8 metals). In the η6-arene/
dithiolene category, only group 8 metal complexes have been
reported (Chart 1).20-24
Introducing these planar π-coordinating organic ligands,
Cp and η6-arene, is plausibly interesting for the structural
chemistry of dithiolenes because the complexes have inter-
molecular π-interactions through the π-coordinating organ-
ic ligand but show strong magnetic interactions in the solid
state while the complexes are paramagnetic. Recently, the
paramagnetic [CpNi(dithiolene)]• (S = 1/2) complexes have
been investigated from combined structural and magnetic
properties.25 For example, the Cp ligand of these complexes
exhibits a Cp dithiolene zigzag chain interaction in
[CpNi(tfd)] (tfd=1,2-bis(trifluoromethyl)ethene-1,2-dithio-
3 3 3
late),26 a Cp SdC interaction in [CpNi(dmit)] (dmit =
3 3 3
1,3-dithiol-2-thione-4,5-dithiolate),25,27 and
a
Cp Cp
3 3 3
dimeric interaction in [CpNi(adt)] (adt = acrylonitrile-1,2-
dithiolate),26 [CpNi(bdt)] (bdt = benzene-1,2-dithiolate),28
and [CpNi(bds)] (bds = benzene-1,2-diselenolate).28
A
theoretical study on [CpNi(dithiolene)] has indicated the
existence of some spin densities on the Cp ligand.25,26,28,29
In addition, the diamagnetic [Cp*Co(dithiolene)] (Cp* = η5-
pentamethylcyclopentadienyl) complexes exhibit Cp*
3 3 3
benzene interactions in the mononuclear Cp*Co with ben-
zene-1,2-dithiolate (bdt),30 the dinuclear (Cp*Co)2 with
benzene-1,2,4,5-tetrathiolate,30 and the trinuclear (Cp*Co)3
with benzenehexathiolate complexes.31 According to rea-
sons noted above, these planar π-coordinating organic
ligands behave also as intermolecular π-interacting ligands.
In this work, we attempted to introduce another planar
π-coordinating and probable π-interacting organic ligand,
η4-cyclobutadiene (η4-C4R4),32 to form a new organometal-
lic dithiolene complex. The dithiolene complex of the
η4-C4R4 ligand has been much less investigated compared
with the Cp and η6-C6R6 dithiolene complexes, because there
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3778 Organometallics, Vol. 28, No. 13, 2009
Nomura et al.
Scheme 1
Results and Discussion
1. Preparations, Characterizations, and Reactivity of
[(η4-C4Me4)Pt(dithiolene)] and [(η4-C4Me4)Pt(diselenolene)]
Complexes. Maitlis et al. have reported the facile preparation
of 1 by the reaction of [Pt(NCMe)2(Cl)2] with 2-butyne in
the presence of SnCl2, and the produced intermediate
[(η4-C4Me4)2Pt2(μ-Cl)3][(η4-C4Me4)Pt(SnCl3)3], when trea-
ted with aqueous HCl, forms 1.39 As shown in Scheme 1,
disodium maleonitrile-1,2-dithiolate (Na2mnt) reacted with
1 in MeOH solution at room temperature to form [(η4-
C4Me4)Pt(mnt)] (2) in 63% yield. The treatment of dimethyl
1,3-dithiol-2-one-4,5-dicarboxylate (OdC(dcmedt)) with 2
equiv of sodium methoxide in MeOH affords the corre-
sponding dithiolate dianion (dcmedt2-), and then successive
addition of 1 gave [(η4-C4Me4)Pt(dcmedt)] (3) in 42% yield. 1
reacted with toluene-3,4-dithiol (H2tdt) in the presence of
excess NEt3 to produce [(η4-C4Me4)Pt(tdt)] (4) in 59% yield.
[(η4-C4Me4)Pt(dddt)] (5) was prepared in 17% yield from
OdC(dddt) by a similar synthetic procedure to that of 3. [(η4-
C4Me4)Pt(dmit)] (6, 64% yield) and [(η4-C4Me4)Pt(dsit)]
(7, 48% yield) were obtained from 1 and (NBu4)2[Zn(dmit)2]
or (NEt4)2[Zn(dsit)2] without any base, respectively
(Scheme 1). The products 2-7 were air stable and could be
separated by column chromatography on silica gel. 2-7
were soluble in dichloromethane, chloroform, acetone, and
benzene. However, 6 and 7 were not soluble enough in
CDCl3 and CD2Cl2 for 13C NMR measurements. The dis-
elenolene complex 7 was less soluble than the others. 2-7
were characterized by spectroscopic data and elemental
analyses.
are some difficulties in the synthetic procedure. One possible
species is a η4-C4R4 complex of the group 10 metals. The
neutral η4-C4R4 ligand with its 4π-electron donation makes
formal MII (d8) dithiolene complexes, which are formulated
as [(η4-C4R4)MIV(dithiolene)] (Chart 1). They become
16-electron half-sandwich dithiolene complexes and are well
comparable with other 16-electron dithiolene complexes
such as [CpMIII(dithiolene)] (MIII = group 9 metals)19
and [(η6-C6R6)MII(dithiolene)] (MII = group 8 metals)
(Chart 1).20-24
The 1H NMR spectra of 2-7 showed four equivalent Me
groups around 1.9-2.1 ppm (vs TMS) and also resulted in
coupling effects due to the Pt satellite (195Pt natural abun-
dance = 33.80% (I = 1/2)), whose JPt-H values were 13-15
Hz (Table 1). The 13C NMR spectra showed equivalent
cyclobutadiene carbons (C4Me4) around 100 ppm (vs
TMS), which are an aromatic region, and also suggested Pt
satellite coupling with JPt-C = ca. 100 Hz (Table 1). These
results indicated an equivalent π-coordination by four car-
bons of the η4-cyclobutadiene ligand to the Pt center.
Furthermore, the 13C NMR spectra of 2-5 exhibited a
JPt-C at the dithiolene carbons, and the toluene-3,4-dithio-
late complex 4 showed a JPt-C at 2,5-carbons on the toluene
moiety as well, but the JPt-C values (JPt-C = 8.4, 8.8 Hz)
were relatively small because of the long distances between
the carbons and the Pt center. In previous papers, [Pt(cod)-
(dithiolene)] (cod = 1,5-cyclooctadiene) complexes have
shown a similar Pt satellite coupling at the dithiolene and
cod carbons, which have been reported by Bereman41 and
Eisenberg42 et al.
Some nickel and palladium complexes of the η4-C4R4
ligand have been reported as follows: [(η4-C4Me4)Ni-
(mnt)] (mnt = maleonitrile-1,2-dithiolate),33,34 [(η4-C4Ph4)-
Pd(mnt)],33 and [(η4-C4(Me)2(tBu)2)Pd(bdt)].35 However,
the highly toxic [Ni(CO)4]36 is required for the (η4-C4R4)Ni
complexes,37 and the Pd complex requires an expensive
asymmetric alkyne as a precursor.38 We noted that no
platinum dithiolene complex of the η4-C4R4 ligand has been
reported, and the possible starting material [(η4-C4Me4)-
Pt(Cl)(μ-Cl)]2 (1) is relatively easy to prepare compared with
the Ni and Pd precursors. The synthetic procedure of 1 has
been developed by Maitlis et al.39,40 Here we report on the
syntheses of five new [(η4-C4Me4)Pt(dithiolene)] (dithiolene =
dcmedt, mnt, tdt, dddt, dmit; see Scheme 1) complexes
from 1 and one [(η4-C4Me4)Pt(diselenolene)] (diselenolene =
dsit) complex as well. These new products were character-
ized by NMR and UV-vis spectra and CV measurements.
Especially, we discuss their crystal structures and review the
intermolecular π-interaction based on the π-interacting
η4-C4Me4 ligand.
The UV-vis spectra of 2-7 were obtained, and the
absorption maxima (λmax/nm) appeared as follows: 2 (430
nm), 3 (439 nm), 4 (449 nm), 5 (535 nm), 6 (512 nm), and
7 (503 nm) as lowest energy absorption bands (Table 2).
These results may indicate that the complex with the
more electron-rich dithiolene ligand shows lower energy
absorption. In fact, these results correlate with those of
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K. R.; Seevogel, K.; Krueger, C. J. Organomet. Chem. 1989, 367, 233.
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(38) Kelley, E. A.; Maitlis, P. M. J. Chem. Soc., Dalton Trans. 1979,
167.
(41) (a) Keefer, C. E.; Bereman, R. D.; Purrington, S. T.; Knight, B.
W.; Boyle, P. D. Inorg. Chem. 1999, 38, 2294. (b) Keefer, C. E.;
Purrington, S. T.; Bereman, R. D.; Boyle, P. D. Inorg. Chem. 1999, 38,
5437.
(42) (a) Cummings, S. D.; Eisenberg, R. Inorg. Chem. 1995, 34, 2007.
(b) Bevilacqua, J. M.; Eisenberg, R. Inorg. Chem. 1994, 33, 2913.
(39) Moreto, J.; Maitlis, P. M. J. Chem. Soc., Dalton Trans. 1980,
1368.
(40) Maitlis, P. M. Acc. Chem. Res. 1976, 9, 93.

Article
Organometallics, Vol. 28, No. 13, 2009 3779
Table 1. 1H NMR and 13C NMR Chemical Shiftsb (δ/ppm vs TMS) and Coupling Constants (JPt-H, JPt-C/Hz) by 195Pt Satellite in CDCl3
1H NMR
C4(CH3)4
13C NMR
C4(CH3)4
JPt-H
JPt-C
dithiolene-C
JPt-C
38.3
80.3
92.4, 93.6
9.6
others
JPt-C
2
3
4
5
6
7
2.11
2.06
2.06
2.02
2.08
1.91
13.2
13.2
13.2
13.7
14.3
15.1
104.8
102.0
100.2
100.3
99.7
98.4
98.4
100.6
102.0
131.8
167.7
130.3, 129.8
129.5
132.6, 124.3
8.4, 8.8
a
102.4
a
a
a No 13C NMR signals were found due to poor solubility. b Only δ values having 195Pt satellite coupling are shown.
Table 2. UV-Vis Spectral Data (λmax/nm (ε/M-1 cm-1)) in
Dichloromethane Solution
3
ligand
(η4-C4Me4)Pt complex
CpNi complex
ref
mnt
dcmedt
tdt
dddt
dmit
dsit
430 (4800) (2)
439 (5200) (3)
449 (9200) (4)
535 (5300) (5)
512 (8000) (6)
503 (7000) (7)
698 (2000)
695 (1500)
722a (2600)
1012 (4700)
967 (6000)
948 (3200)
43
43
28
28
28
28
a Benzene-1,2-dithiolate (bdt) ligand was used instead of tdt.
Table 3. Redox Potentials (vs Fc/Fc+) of 2-7 Obtained from CVa
Ep(red)/V
Ep(ox)/V
|Epa - Epc|/mV ipa/ipc Ep(2ox)/V
b
2
3
4
5
6
7
-1.74 (ir) +1.08 (ir)
-2.06 (ir) +0.74 (ir)
-2.11 (ir) +0.45 (ir)
(ir)
(ir)
(ir)
165
177
156
(ir)
(ir)
(ir)
1
0.65
0.50
b
b
-2.12 (ir)
0c (qr)
0.88 (ir)
+1.02 (ir)
+1.04 (ir)
-1.88 (ir) +0.35c (qr)
-1.85 (ir) +0.26c (qr)
a Ep = peak potentials. |Epa - Epc| = peak-to-peak separation. ipa/ipc
=
Figure 1. Cyclic voltammograms of 2-7 in dichloromethane
ratio of peak current. b Not observed in the potential window of dichlor-
omethane-TBAP. c Half-wave potentials (E1/2/V) were used. (qr) and (ir):
quasi-reversible and irreversible waves, respectively.
solution containing 0.1 M TBAP (c = 1.0 mmol dm-3, Φ = 1.6
3
mm Pt disk as a working electrode, v = 100 mV s-1).
3
are shown in Figure 1. Their reduction waves were comple-
tely irreversible, and the first oxidation waves of 2-4 were
also irreversible. These results explain that the reduced or
oxidized species are unstable on the CV time scale. In
contrast, the first oxidation waves of 5, 6, and 7 looked
quasi-reversible (Figure 1), because the peak-to-peak separa-
tion |Epa - Epc| values are 156-177 mV (Table 3). These
facts indicate that an electron-rich dithiolene ligand stabi-
lizes the oxidized complex. According to the ipa/ipc ratios, the
oxidized species of 5 is stable enough on the CV time scale
(ipa/ipc = 1), but those of 6 and 7 are less stable than that
of 5 (ipa/ipc = 0.65 and 0.50, respectively). The reduction
potential of 2-7 appeared in the range between -1.74 (mnt)
and -2.12 V (dddt). In contrast, the CVs indicated a wide
range of first oxidation potentials (Table 3). Although
2 (mnt) was oxidized at +1.08 V, 5 (dddt) was oxidized at
0 V (Table 3).
[CpNi(dithiolene)] and [CpNi(diselenolene)] complexes as
follows (Table 2): [CpNi(mnt)] (698 nm), [CpNi(dcmedt)]
(695 nm),43 [CpNi(bdt)] (722 nm), [CpNi(dmit)] (967 nm),
[CpNi(dsit)] (948 nm), and [CpNi(dddt)] (1012 nm).28 In the
square-planar complexes of bisdithiolene, the electron-rich
complexes [M(dddt)2],44 [M(dmit)2],44 [M(S2C2Fc2)2] (Fc =
ferrocenyl),45 and [M(R,R0timdt)2] (R,R0timdt = N,N0-disub-
stituted imidazolidine-2,4,5-trithione)46 indicated strong NIR
absorption. The low-energy absorption of the neutral or
monoanionic [M(dithiolene)2]n- complexes can be attributed
to the ligand-to-ligand charge transfer,10 and that of [Pt
(dithiolene)(N N)] (N N=2,2’-bipyridines, 1,10-phenanthro-
lines) can be assigned also to ligand(dithiolene)-to-ligand(N
N).12 The latter absorption is usually solvatochromic, and it
depends on the polarity of the solvent.12b
The redox potentials (vs Fc/Fc+) taken from CV measure-
ment are described in Table 3. These cyclic voltammograms
These results supported that modification of the dithiolene
ligand has a greater effect on oxidation potentials than
reduction potentials. Namely, the complexes of electron-rich
dithiolene ligands such as dddt, dmit, and dsit (5-7) have
higher energy HOMO levels, and eventually the HOMO-
LUMO gaps of 5-7 (503-535 nm) are much lower than
those of the others (430-449 nm). We may conclude that
the first oxidation of the [(η4-C4Me4)Pt(dithiolene)] complex
is based on the dithiolene ligand, and the first reduction is
due to the Pt center, because ligand modification does not
well contribute to the reduction potential. Normally, the
(43) Nomura, M.; Okuyama, R.; Fujita-Takayama, C.; Kajitani, M.
Organometallics 2005, 24, 5110.
(44) (a) Mueller-Westerhoff, U. T.; Yoon, D. I.; Plourde, K. Mol.
Cryst. Liq. Cryst. 1990, 183, 291. (b) Mueller-Westerhoff, U. T.; Vance,
B.; Yoon, D. I. Tetrahedron 1991, 47, 909.
(45) Mueller-Westerhoff, U. T.; Sanders, R. W. Organometallics
2003, 22, 4778.
(46) (a) Aragoni, M. C.; Arca, M.; Demartin, F.; Devillanova, F. A.;
Garau, A.; Isaia, F.; Lelj, F.; Lippolis, V.; Verani, G. J. Am. Chem. Soc.
1999, 121, 7098. (b) Arca, M.; Demartin, F.; Devillanova, F. A.; Garau,
A.; Isaia, F.; Lelj, F.; Lippolis, V.; Pedraglio, S.; Verani, G. J. Chem.
Soc., Dalton Trans. 1998, 3731.

3780 Organometallics, Vol. 28, No. 13, 2009
Nomura et al.
Figure 2. (a) Projection view along the a axis of 2 showing an inversion-centered dyad arrangement, (b) inversion-centered dyad of
[CpNi(mnt)], and (c) crisscross dyad of [CpNi(mnt)].43 Both (b) and (c) dyads are observed in the same unit cell.
Scheme 2
homoleptic dithiolene complexes [M(dithiolene)2] (M=Ni, Pd,
Pt) have a dithiolene ligand-based HOMO and LUMO. In
total, five different oxidation states (-2, -1, 0, +1, +2) have
been observed, because the dithiolene ligand itself involves
dithiolate (-2), dithiosemiquinone (-1), and dithioketone
(0).10 In addition, the heteroleptic dithiolene complexes
[Pt(dithiolene)(N N)] can be reduced at the N N moiety and
oxidized at the dithiolene ligand. Eventually, four different
oxidation states (-2, -1, 0, +1) were observed.12
Figure 3. ORTEP drawing of 3. Thermal ellipsoids are drawn at
the 30% probability level. All hydrogen atoms are omitted for
simplicity.
The reactivity of [(η4-C4Me4)Pt(dithiolene)] complexes
was investigated. The reaction of 3 with bis(diphenylpho-
sphino)ethane (DPPE) at room temperature gave the
square-planar Pt dithiolene complex that was formulated
as [Pt(dcmedt)(dppe)]47 in quantitative yield (Scheme 2).
This result suggests a ligand exchange reaction between
DPPE and the η4-C4Me4 ligand, followed by nucleophilic
attack of DPPE to the Pt center. Mashima et al. have
reported the synthesis of [(η4-C4(Me)2(tBu)2)Pd(bdt)]35 and
also its reactivity with PEt3 or isocyanide (CNR) to form the
corresponding square-planar Pd complex [Pd(bdt)(PEt3)2]
or [Pd(bdt)(CNR)2], respectively.35 Additionally, the cod
ligand in [Pt(cod)(dithiolene)] has also been substituted by
diphosphines or monophosphines to obtain the luminescent
[Pt(dithiolene)(P2)] complexes.42,48 Here we propose that
[(η4-C4Me4)Pt(dithiolene)] is also an important precursor
of the luminescent Pt dithiolene complexes and asymmetric
dithiolene complexes.
Figure 4. (a) Projection view along the c axis of 5 and the
zigzag-shaped intermolecular interaction running along the
a axis through the η4-C4Me4 dithiolene interaction. (b) Over-
3 3 3
lap pattern of η4-C4Me4 dithiolene stacking from the top
view.
3 3 3
2. X-ray Crystal Structure Analyses of [(η4-C4Me4)Pt-
(dithiolene)] and [(η4-C4Me4)Pt(diselenolene)] Complexes.
Single crystals of the products except for 4 were obtained
from recrystallization of dichloromethane/n-hexane solu-
tion. The ORTEP drawings and packing diagrams are
shown in Figures 2-6. Table 4 exhibits selected bond
lengths, bond angles, and dihedral angles. These crystal data
are summarized in Table 5. All molecules 2, 3, and 5-7 are
monomeric at room temperature, and each η4-C4Me4 ligand
is located in a perpendicular position with respect to the
Pt-dithiolene or Pt-diselenolene ring because the dihedral
angles of η4-C4Me4/PtE2 (E = S, Se) are almost 90°.
Thus, they have typical two-legged piano-stool geometries.
As shown in Table 4 for mean planes, the η4-C4Me4 and
PtE2C2 (E= S, Se) rings are extremely planar. Some dimeric
[CpM(dichalcogenolene)]2 and [Cp*M(dichalcogenolene)]2
with group 9 metal complexes have been reported in
(47) Ford, S.; Lewtas, M. R.; Morley, C. P.; Vaira, M. D. Eur.
J. Inorg. Chem. 2000, 933.
(48) Bevilacqua, J. M.; Zuleta, J. A.; Eisenberg, R. Inorg. Chem. 1994,
33, 258.

Article
Organometallics, Vol. 28, No. 13, 2009 3781
˚
Table 4. Selected Bond Lengths (A), Bond Angles (deg), and
Dihedral Angles (deg) in the PtE2C2 Metallacycle (E =S, Se)
2
3
5
6
7
Bond Lengths
Pt1-E1
Pt1-E2
E1-C1
E2-C2
C1-C2
2.277(3) 2.2594(10) 2.2714(9) 2.2856(17) 2.3955(7)
2.265(3) 2.2742(10) 2.2735(9) 2.2793(19) 2.3871(6)
1.724(11) 1.741(3) 1.735(4) 1.737(7) 1.895(6)
1.732(10) 1.733(4) 1.741(4) 1.719(7) 1.878(6)
1.343(15) 1.350(5) 1.355(5) 1.347(8) 1.330(7)
Bond Angles
Figure 5. ORTEP drawing of 7. Thermal ellipsoids are drawn at
the 30% probability level. All hydrogen atoms are omitted for
simplicity.
E1-Pt1-E2
Pt1-E1-C1
Pt1-E2-C2
E1-C1-C2
E2-C2-C1
89.71(10) 89.22(3) 89.00(3) 90.81(6) 92.83(2)
102.4(3) 103.82(13) 103.05(12) 101.1(2) 98.80(18)
102.7(3) 103.24(14) 103.00(14) 101.1(2) 99.16(17)
122.9(8) 121.3(3) 121.9(3) 122.6(5) 124.1(5)
122.3(8) 122.4(3) 121.7(3) 124.3(5) 124.8(5)
Dihedral Angle
η4-C4Me4/PtE2 91.805
89.254
96.083
92.539
87.027
Mean Plane
η4-C4Me4
PtE2C2
0.0088
0.0051
0.0012
0.0068
0.0064
0.1049
0.0057
0.0375
0.0108
0.0594
2-
S2- (1.70 A) and Se (1.84 A).57 Each cyclobutadiene ring is
rectangular as normally well-known in any η4-cyclobuta-
diene metal complex. For example, the C-C bond lengths in
the cyclobutadiene carbons (C5-C8) in 2 are as follows:
C5-C6=1.493(17), C5-C8=1.429(18), C6-C7=1.42(2),
˚
˚
˚
C7-C8 = 1.492(18) A.
The dmit complex 6 is crystallographically isostructural to
the corresponding selenium complex 7 (Table 5). Both com-
plexes crystallized as a monoclinic system, space group P21/n,
with one independent molecule in general position in the unit
cell. Such crystallographic similarity between dithiolene and
diselenolene complexes has been found as follows: [CpNi-
(dmit)] vs [CpNi(dsit)],27 [CpNi(bdt)] vs [CpNi(bds)],28 [CpNi-
(dddt)] vs [CpNi(ddds)] (ddds = 5,6-dihydro-1,4-dithiin-2,3-
diselenolate),28 and [CpCo(bdt)]249 vs [CpCo(bds)]2.50
Figure 6. (a) Crystal-packing diagram of 6 showing the
zigzag-shaped interaction running along the b axis through
the η4-C4Me4 trithiocarbonate interaction. (b) Overlap pat-
3 3 3
tern of η4-C4Me4 trithiocarbonate stacking from the top
view.
3 3 3
[CpCo(bdt)]2,49 [CpCo(bds)]2 (bds = benzene-1,2-diseleno-
late),50 [Cp*Rh(mnt)]2,51 [Cp*Rh(bdt)]2,52 and [Cp*Rh-
(dmit)]2.53 In the group 10 metal complexes of Cp and
η4-C4R4 ligands, no dimeric species has been observed.
The bond lengths in the metallacycle of [(η4-C4Me4)Pt-
The packing diagram of 2 demonstrated an inversion-
centered dyad in the unit cell. Two molecules are stacked
along the a axis (Figure 2a). The intermolecular distance
˚
between two molecules is ca. 3.8 A. According to early
˚
(dithiolene)] complexes are 2.26-2.28 A for Pt-S, 1.72-1.74
studies, the monomeric [CpM(mnt)] complexes have tended
to show an intermolecular dimeric interaction. In the CpCo
and CpNi complexes of mnt,43,58 there are two different
dyads. One is an inversion-centered dyad type as displayed in
Figure 2b, and the other is a crisscross type whose two
molecules are shifted at 90° (Figure 2c).43,58 In addition,
the monomeric [Cp*Ir(mnt)] complex has been reported.
There are two crystallographically independent molecules
in the unit cell. The same molecules interact as an inversion-
centered dyad.59 On the other hand, 3 does not have any
specific intermolecular interactions due to bulkiness of the
two ester groups. 5 crystallized as a monoclinic system, space
group P21/a, with one molecule in the unit cell. Figure 4
˚
˚
A for S-C, and 1.34-1.35 A for CdC bonds (Table 4).
These bond lengths are similar to those of the corres-
ponding square-planar Pt bisdithiolene complexes such as
[Pt(mnt)2]-,54 [Pt(dddt)2]-,55 and [Pt(dmit)2]-,56 and slightly
different from that of the diselenolene complex 7 (Table 4).
The difference of bond length between dithiolene and
diselenolene complexes is due to the atomic radius between
(49) Miller, E. J.; Brill, T. B.; Rheingold, A. L.; Fultz, W. C. J. Am.
Chem. Soc. 1983, 105, 7580.
(50) Habe, S.; Yamada, T.; Nankawa, T.; Mizutani, J.; Murata, M.;
Nishihara, H. Inorg. Chem. 2003, 42, 1952.
(51) Don, M.-J.; Yang, K.; Bott, S. G.; Richmond, M. G. J. Organo-
met. Chem. 1997, 544, 15.
(52) Xi, R.; Abe, M.; Suzuki, T.; Nishioka, T.; Isobe, K. J. Organo-
met. Chem. 1997, 549, 117.
indicates an intermolecular η4-C4Me4 dithiolene interac-
3 3 3
˚
tion whose plane-to-plane distance is ca. 3.7 A. The whole
(53) Kawabata, K.; Nakano, M.; Tamura, H.; Matsubayashi, G.
J. Organomet. Chem. 2004, 689, 405.
packing diagram exhibited a zigzag-shaped intermolecular
chain along the a axis in the unit cell. Some early papers have
(54) (a) Guentner, W.; Gliemann, G.; Klement, U.; Zabel, M. Inorg.
Chim. Acta 1989, 165, 51. (b) Clemenson, P. I.; Underhill, A. E.;
Hursthouse, M. B.; Short, R. L. J. Chem. Soc., Dalton Trans. 1989, 61.
(55) Welch, J. H.; Bereman, R. D.; Singh, P. Inorg. Chim. Acta 1989,
163, 93.
(57) Fujiwara, H.; Ojima, E.; Kobayashi, H.; Courcet, T.; Malfant, I.;
Cassoux, P. Eur. J. Inorg. Chem. 1998, 1631.
(58) Takayama, C.; Kajitani, M.; Sugiyama, T.; Sugimori, A.
J. Organomet. Chem. 1998, 563, 161.
(59) Ren, C.-X.; Ding, Y.-Q. Acta Crystallogr. 2007, E63, m249.
(56) Mentzafos, D.; Hountas, A.; Terzis, A. Acta Crystallogr. 1988,
C44, 1550.

3782 Organometallics, Vol. 28, No. 13, 2009
Nomura et al.
Table 5. Crystallographic Data
2
3
5
6
7
formula
fw (g mol-1
cryst color
cryst shape
C
443.45
orange
needle
12H12N2PtS2
C14H18O4PtS2
509.50
orange
C12H16PtS4
483.59
dark red
block
C11H12PtS5
499.61
red
C11H12PtS3Se2
593.41
red
)
3
block
block
block
cryst size (mm)
cryst syst
0.30ꢀ0.05ꢀ0.05
monoclinic
P21/n (No. 14)
298
7.8569(7)
16.0720(13)
11.4186(10)
94.1190(15)
1438.2(2)
4
2.048
9.987
10 963
3223 (0.042)
2788
0.0572
0.16ꢀ0.10ꢀ0.10
monoclinic
P21/a (No. 14)
298
13.3701(19)
9.6363(14)
13.491(2)
90.8299(5)
1737.9(4)
4
1.947
8.292
12 779
3933 (0.032)
3397
0.0284
0.21ꢀ0.21ꢀ0.18
monoclinic
P21/a (No. 14)
298
11.429(2)
9.9809(19)
13.087(3)
96.6553(7)
1482.8(5)
4
2.166
9.964
11 231
3393 (0.029)
2908
0.0232
0.07ꢀ0.05ꢀ0.03
monoclinic
P21/n (No. 14)
298
8.489(2)
14.062(4)
12.994(3)
102.6420(9)
1513.5(7)
4
2.192
9.898
11 771
3344 (0.035)
2486
0.0276
0.15ꢀ0.10ꢀ0.05
monoclinic
P21/n (No. 14)
298
8.588(2)
14.183(4)
13.174(4)
102.3993(11)
1567.3(7)
4
2.515
13.938
12 036
3500 (0.040)
2743
0.0288
space group
T (K)
˚
a (A)
˚
b (A)
˚
c (A)
β (deg)
3
V (A )
˚
Z
Dcalc (g cm-3
)
3
μ (mm-1
)
total reflns
unique reflns (Rint
)
unique reflns (I > 2σ(I))
R (I > 2σ(I))a
wR (I > 2σ(I))a
goodness-of-fit
0.1656
1.036
0.0783
1.025
0.0706
1.014
0.0826
1.022
0.0822
1.067
reported that the dithiolene ring interacts with other organic
aromatic rings, which involves Cp dithiolene26 and ben-
have been reported.62 The η4-C4Me4 ligand with group 10
metals can be used instead of Cp and η6-arene complexes. (2)
Introduction of the η4-Si4Me4 ligand is possible instead
of the η4-cyclobutadiene ligand,63 although η5-Si5R5 and
η6-Si6R6 π-coordination is not possible yet. They will be new
heteroleptic dithiolene complexes. (3) Electron-rich com-
plexes 5 (dddt) and 6 (dmit) are electrochemically and
reversibly oxidized (Figure 1). The oxidized species can be
paramagnetic and might be conductive. An intermole-
cular magnetic interaction through plane-to-plane interac-
tion by the π-interacting η4-C4Me4 ligand and conducting
behavior through the zigzag interaction (Figures 4 and 6)
can be expected. (4) The [(η4-C4Me4)Pt(dithiolene)] and
[(η4-C4Me4)Pt(diselenolene)] complexes are useful precur-
sors for luminescent Pt complexes12,42,48 through ligand
exchange reaction of η4-C4Me4 ligand with nucleophiles such
as N N, P P, As As, and S S bidentate (or two monodentate)
ligands. This reactivity indicates the formation of new
asymmetric dithiolene complexes.
3 3 3
zene dithiolene interactions.60 In addition, a dithiolene
3 3 3
3 3 3
dithiolene interaction has been reported as well.61 Most
probably, these π-interactions are due to the aromaticity and
good planarity of the dithiolene ring.2 In the dmit complex 6,
the η4-C4Me4 ligand interacts with the trithiocarbonate
moiety (C2S2CdS). The packing diagram of 6 (Figure 6)
displays
plane-to-plane distance is ca. 3.7 A. The dsit complex 7 also
showed a similar interaction to 6 because they are isostruc-
a zigzag-shaped intermolecular chain whose
˚
tural with each other. The η4-C4Me4 C2S2CdS plane-to-
3 3 3
˚
plane distance is 3.7 A.
Conclusion
In this work, we reported the preparation, spectroscopic
characterization, electrochemical behavior, chemical reactivity,
and crystal structures of the [(η4-C4Me4)Pt(dithiolene)] and
[(η4-C4Me4)Pt(diselenolene)] complexes. Although rich organo-
metallic dithiolene complexes of Cp and η6-arene ligands have
been reported, this work has described an introduction of the
new planar organic η4-C4Me4 ligand to prepare organometallic
dithiolene complexes (Chart 1). In conclusion, the η4-C4Me4
ligand behaves as a π-coordinating ligand to form the 16-
electron dithiolene complexes of group 10 metals (NiII, PdII,
PtII), but also behaves as a π-interacting ligand to form some
intermolecular plane-to-plane interactions in the crystal. How-
ever, the π-coordination of the η4-C4Me4 ligand to the metal was
not enough strong, because it was replaced by other nucleo-
philes (Scheme 2).
Experimental Section
General Remarks. All reactions were carried out under an
argon atmosphere by means of standard Schlenk techniques.
All solvents for reactions were purified by using CaH2 for
MeOH and dichloromethane before use. [Pt(NCMe)2(Cl)2],64
[(η4-C4Me4)Pt(Cl)(μ-Cl)]2 (1),39 disodium maleonitrile-1,2-dithiolate
(62) (a) Muratsugu, S.; Sodeyama, K.; Kitamura, F.; Sugimoto, M.;
Tsuneyuki, S.; Miyashita, S.; Kato, T.; Nishihara, H. J. Am. Chem. Soc.
2009, 131, 1388. (b) Nakagawa, N.; Murata, M.; Sugimoto, M.; Nishihara,
H. Eur. J. Inorg. Chem. 2006, 2129. (c) Murata, M.; Habe, S.; Araki, S.;
Namiki, K.; Yamada, T.; Nakagawa, N.; Nankawa, T.; Nihei, M.;
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(d) Nakagawa, N.; Yamada, T.; Murata, M.; Sugimoto, M.; Nishihara, H.
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Here we have reported only basic studies for [(η4-C4Me4)-
Pt(dithiolene)] and [(η4-C4Me4)Pt(diselenolene)] complexes.
However, these complexes will be interesting for other
chemical, photophysical, and solid state properties for
the following reasons: (1) Heteronuclear cluster complexes
of [{CpM(dithiolene)}2M0(CO)n] (M = group 9 metals) or
[{(η6-arene)M(dithiolene)}2M0(CO)n] (M = group 8 metals)
(60) Nomura, M.; Kajitani, M. J. Organomet. Chem. 2006, 691, 2691.
ꢀ
(61) Nomura, M.; Geoffroy, M.; Adkine, P.; Fourmigue, M. Eur. J.
Inorg. Chem. 2006, 5012.
(64) Bailey, P. M.; Mann, B. E.; Brown, I. D.; Maitlis, P. M. J. Chem.
Soc., Chem. Commun. 1976, 238.

Article
Organometallics, Vol. 28, No. 13, 2009 3783
(Na2mnt),65 dimethyl 1,3-dithiol-2-one-4,5-dicarboxylate (OdC-
(dcmedt)),66 OdC(dddt),67 (NBu4)2[Zn(dmit)2],68 and (NEt4)2[Zn-
(dsit)2]69 were prepared by literature methods. 2-Butyne, SnCl2
(for 1), toluene-3,4-dithiol, NEt3, and silica gel (Wakogel C-300)
were obtained from Wako Pure Chemical Industries, Ltd. Sodium
methoxide in MeOH solution was prepared from dry MeOH
and fresh sodium metal. Mass spectra were recorded on a
(20 mL). An orange solution was rapidly obtained, and the
reaction mixture was further stirred for 3 h. After the reaction,
the solvent was removed under reduced pressure. The residue
was separated by column chromatography on silica gel with
dichloromethane eluent. The resulting orange solid was recrys-
tallized from dichloromethane and n-hexane (1:1). 4 was ob-
tained in 59% yield.
[(η4-C4Me4)Pt(tdt)] (4). Mass (EI+, 70 eV): m/z (rel intensity)
457 ([M+], 100), 442 ([M+ - Me], 38), 349 ([M+-C4Me4], 25).
1H NMR (CDCl3, 500 MHz, vs TMS): δ 7.80 (d, J = 8.0 Hz, 1H,
benzene), 7.74 (d, J = 1.7 Hz, 1H, benzene), 6.83 (dd, J = 8.0,
1.7 Hz, 1H, benzene), 2.37 (s, 3H, Me), 2.06 (s with Pt satellites,
JPt-H = 13.2 Hz, 12H, Me). 13C NMR (CDCl3, 125 MHz, vs
TMS): δ 149.2 (s, benzene), 146.0 (s, benzene), 132.6 (s with Pt
JEOL JMS-D300. NMR spectra were measured with
a
JEOL LA500 spectrometer. The 1H and 13C chemical shifts (δ in
ppm) are referenced using chemical shifts of TMS at δ 0 ppm.
Chloroform-d was purchased from Aldrich Chemicals. UV-
vis spectra were recorded on a Hitachi model UV-2500PC. Ele-
mental analyses were determined by using a Shimadzu PE2400-II
instrument.
Preparation of [(η4-C4Me4)Pt(mnt)] (2). A mixture of 1 (187
mg, 0.25 mmol) and Na2(mnt) (93 mg, 0.5 mmol) was stirred in
MeOH (20 mL) at room temperature for 3 h. An orange cloudy
solution was obtained. After the reaction, the solvent was
removed under reduced pressure. The mixture was separated
by column chromatography on silica gel (eluent: dichloro-
methane). The resulting orange solid was further purified by
recrystallization from dichloromethane/n-hexane (1:1). The or-
ange product 2 was obtained in 63% yield.
satellites, JC-Pt = 8.4 Hz, benzene), 130.3 (s with Pt satellites, JC-Pt
=
92.4 Hz, benzene), 129.8 (s with Pt satellites, JC-Pt = 93.6 Hz,
benzene), 124.3 (s with Pt satellites, JC-Pt = 8.8 Hz, benzene),
100.2 (s with Pt satellites, JC-Pt = 97.8 Hz, C4Me4), 20.6 (s, Me),
9.0 (s, C4Me4). UV-vis (CH2Cl2): λmax/nm (ε/M-1 cm-1
449 (9200). Anal. Calcd for C15H18PtS2: C, 39.38; H, 3.97.
Found: C, 39.53; H, 3.84.
)
3
Preparation of [(η4-C4Me4)Pt(dddt)] (5). Sodium methoxide
(1.1 mmol) was added into a methanol solution (20 mL) of OdC
(dddt) (104 mg, 0.5 mmol) for 1 h at room temperature. The
initial colorless solution changed to yellow. 1 (187 mg, 0.25
mmol) was successively added to the reaction mixture and
further stirred for 3 h at room temperature. After the solvent
was removed under reduced pressure, the resulting mixture was
separated by column chromatography on silica gel. A red
fraction was extracted with dichloromethane. The resulting
red solid was further purified by recrystallization from dichlor-
omethane/n-hexane (1:1). The dark red crystal 5 was obtained in
17% yield.
[(η4-C4Me4)Pt(mnt)] (2). Mass (EI+, 70 eV): m/z (rel inten-
sity) 443 ([M+], 100), 428 ([M+ - Me], 15), 335 ([M+ - C4Me4],
1
48). H NMR (CDCl3, 500 MHz, vs TMS): δ 2.11 (s with Pt
satellites, JPt-H = 13.2 Hz, 12H, Me). 13C NMR (CDCl3, 125
MHz, vs TMS): δ 131.8 (s, dithiolene-C), 117.5 (s, CN), 104.8 (s
with Pt satellites, JC-Pt = 99.7 Hz, C4Me4), 9.3 (C4Me4). UV-
vis (CH2Cl2): λmax/nm (ε/M-1 cm-1) 267 (34 700), 430 (4800).
3
Anal. Calcd for C12H12N2PtS2: C, 32.50; H, 2.73; N, 6.32.
Found: C, 32.39; H, 2.46; N, 6.38.
Preparation of [(η4-C4Me4)Pt(dcmedt)] (3). Dimethyl 1,3-
dithiole-2-one-4,5-dicarboxylate, OdC(dcmedt) (380 mg, 1.62
mmol), was treated with 2 equiv of sodium methoxide in
methanol solution (50 mL) at room temperature. The colorless
solution changed to yellow after 1 h. When 1 (464 mg, 0.62
mmol) was added to this solution, the yellow solution changed
to brown. The reaction mixture was stirred at room temperature
for 24 h. After the solvent was removed under reduced pressure,
the residue was extracted and the organic layer was purified by
column chromatography on silica gel (eluent: dichloro-
methane). The product 3 was recrystallized with dichloro-
methane/n-hexane (1:1) and obtained as an orange solid in
42% yield.
[(η4-C4Me4)Pt(dddt)] (5). Mass (EI+, 70 eV): m/z (rel inten-
sity) 483 ([M+], 100), 468 ([M+ - Me], 3), 303 ([(C4Me4)Pt+],
38). 1H NMR (CDCl3, 500 MHz, vs TMS): δ 3.18 (s, 4H, CH2),
2.02 (s with Pt satellites, JPt-H = 13.7 Hz, 12H, Me). 13C NMR
(CDCl3, 125 MHz, vs TMS): δ 129.5 (s with Pt satellites, JC-Pt
9.6 Hz, dithiolene-C), 100.3 (s with Pt satellites, JC-Pt
=
=
100.8 Hz, C4Me4), 31.3 (s, CH2), 9.0 (s, C4Me4). UV-vis
(CH2Cl2): λmax/nm (ε/M-1 cm-1) 414 (1900), 535 (5300). Anal.
Calcd for C12H16PtS4: C, 29.80; H, 3.33. Found: C, 29.70; H,
3
3.13.
Preparations of [(η4-C4Me4)Pt(dmit)] (6) and [(η4-C4Me4)Pt-
(dsit)] (7). A mixture of 1 (187 mg, 0.25 mmol) and (NBu4)2[Zn-
(dmit)2] (236 mg, 0.25 mmol) was stirred in MeOH (20 mL) at
room temperature for 3 h. After the solvent was removed, the
mixture was separated by column chromatography on silica gel
with dichloromethane eluent. The resulting red solid was re-
crystallized from dichloromethane/n-hexane (1:1) to obtain 6 as
a red crystal in 64% yield. 7 (red crystal, 48% yield) was
obtained from (NEt4)2[Zn(dsit)2] by using a similar method to
that for 6.
[(η4-C4Me4)Pt(dcmedt)] (3). Mp: 219-221 °C. Mass (EI+, 70
eV): m/z (rel intensity) 509 ([M+], 100), 478 ([M+-OMe], 22.3),
1
450 ([M+ - COOMe], 15), 391 ([M+ - (COOMe)2], 23). H
NMR (CDCl3, 500 MHz, vs TMS): δ 3.98 (s, 6H, OMe), 2.06 (s
with Pt satellites, JPt-H=13.2 Hz, 12H, Me). 13C NMR (CDCl3,
125 MHz, vs TMS): δ 167.7 (s, dithiolene-C), 167.7 (d, JC-Pt
80.3 Hz, dithiolene-C), 146.7 (s, CdO), 102.0 (s with Pt satellites,
C-Pt=98.4 Hz, C4Me4), 52.8 (s, OMe), 9.1 (s, C4Me4). IR (KBr
=
J
disk): 2945, 1719, 1701, 1508, 1425, 1254, 1240, 1072, 1022 cm-1
.
[(η4-C4Me4)Pt(dmit)] (6). Mass (EI+, 70 eV): m/z (rel inten-
UV-vis (CH2Cl2): λmax/nm (ε/M-1 cm-1) 263 (29 000), 439
sity) 499 ([M+], 100), 484 ([M+ -Me], 4), 391 ([M+ - C4Me4],
3
1
(5200). Anal. Calcd for C14H18O4PtS2: C, 33.00; H, 3.56 Found:
C, 32.87; H, 3.28.
4). H NMR (CDCl3, 500 MHz, vs TMS): δ 2.08 (s with Pt
satellites, JPt-H = 14.3 Hz, 12H, Me). 13C NMR (CDCl3, 125
MHz, vs TMS): δ 144.6 (s, dithiolene-C), 102.4 (s with Pt
satellites, JC-Pt = 102.0 Hz, C4Me4), 9.2 (s, C4Me4), doublet
signal at 144.6 ppm and signal for CdS are not observed due to
poor solubility of the sample. UV-vis (CH2Cl2): λmax/nm (ε/
Preparation of [(η4-C4Me4)Pt(tdt)] (4). Two drops of NEt3
(excess) was added into the stirring solution of 1 (187 mg, 0.25
mmol) and toluene-3,4-dithiol (78 mg, 0.5 mmol) in MeOH
M-1 cm-1) 267 (26 300), 433 (15 200), 512 (8000). Anal. Calcd
3
(65) Holm, R. H.; Davison, A. Inorg. Synth. 1967, 10, 8.
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Commun. 1996, 205. (b) Challenger, F.; Mason, E. A.; Holdsworth, E. C.;
Emmott, R. J. Chem. Soc. 1953, 292.
(67) Liu, S.-G.; Wu, P.-J.; Liu, Y.-Q.; Zhu, D.-B. Phosphorus, Sulfur
Silicon Relat. Elem. 1995, 106, 145.
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Sulfur Silicon Relat. Elem. 1979, 7, 49.
(69) Poleschner, H.; Radeglia, R.; Fuchs, J. J. Organomet. Chem.
1992, 427, 213.
for C11H12PtS5: C, 26.44; H, 2.42. Found: C, 26.19; H, 2.21.
[(η4-C4Me4)Pt(dsit)] (7). Mass (EI+, 70 eV): m/z (rel intensity)
594 ([M+], 100). 1H NMR (CDCl3, 500 MHz, vs TMS): δ 1.91 (s
with Pt satellites, JPt-H = 15.1 Hz, 12H, Me). The 13C NMR
was not obtained due to poor solubility of the sample. UV-vis
(CH2Cl2): λmax/nm (ε/M-1 cm-1) 274 (30 200), 424 (17 100),
3
503 (7000). Anal. Calcd for C11H12PtS3Se2: C, 22.26; H, 2.04.
Found: C, 22.34; H, 2.15.

3784 Organometallics, Vol. 28, No. 13, 2009
Nomura et al.
Reaction of 3 with DPPE. A dichloromethane solution
(10 mL) of 3 (51 mg, 0.1 mmol) and DPPE (40 mg, 0.1 mmol)
was stirred at room temperature for 1 h. An orange product was
separated by column chromatography on silica gel with dichlor-
omethane. The orange product [Pt(dcmedt)(dppe)] was ob-
tained in quantitative yield. The [Pt(dcmedt)(dppe)] was
identified with the same product in the literature.47
Electrochemical Measurements. All electrochemical measure-
ments were performed under an argon atmosphere. Solvents for
electrochemical measurements were dried by molecular sieves
4A before use. A platinum wire served as a counter electrode,
and the reference electrode is Ag/AgCl corrected for junction
potentials by referencing internally to the ferrocene/ferrocenium
(Fc/Fc+) couple. Cyclic voltammetry was measured with model
were made on a Rigaku Mercury CCD diffractometer with
˚
graphite-monochromated Mo KR radiation (λ = 0.71073 A).
Each structure was solved by direct methods and expanded using
Fourier techniques.70 The non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were introduced at calculated
positions (riding model) and included in structure factor calcula-
tions, and these were not refined. Absorption corrections were
applied. All calculations were performed using the Crystal Struc-
ture software package.71 Crystallographic data are summarized
in Table 5.
Supporting Information Available: Crystallographic data,
atomic coordinates, bond distances, bond angles, and anisotro-
pic displacement parameters for 2, 3, and 5-7 in CIF format.
These materials are available free of charge via the Internet at
http://pubs.acs.org.
CV-50W of BAS Co. Sample complexes were done in 1 mmol
dm-3 dichloromethane solutions of complexes containing
3
0.1 mol dm-3 tetra-n-butylammonium perchlorate (TBAP) at
3
(70) Beurstkens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykala, C. The
DIRDIF Program System, Technical Report of the Crystallography
Laboratory; University of Nijmegen: Nijmegen, The Netherlands, 1992.
(71) Crystal Structure 3.6.0, Single Crystal Structure Analysis Soft-
ware; Molecular Structure Corp. and Rigaku Corp.: The Woodlands,
TX, and Tokyo, Japan, 2004.
25 °C. A stationary platinum disk (1.6 mm in diameter) was used
as a working electrode.
X-ray Diffraction Study. Single crystals of 2, 3, and 5-7 were
obtained by recrystallization from dichloromethane solutions
and then vapor diffusion of n-hexane into those solutions.
Crystals were mounted on top of a thin glass fiber. Measurements