Oxidative access to flexible {Pt2(μ-SAr)2} square motifs from platinum thiolato complexes with chelating diphosphine

Article abstract of DOI:10.1016/j.jorganchem.2012.07.001

Platinum(II) aryl thiolate complexes formulated as (P2)Pt(SAr)₂ are prepared from the chelating bis(diphenylphosphino)dimethyltetrathiafulvalene (P2), with aryl thiolate ligands (SAr), such as benzenethiolate (BT) and 3,5-dimethylbenzenethiolate (DMBT). The structurally characterized neutral (P2)Pt(SAr)₂ complexes afford, upon oxidation with TCNQF₄, dicationic bimetallic Pt(II) complexes formulated as [(P2)Pt(μ-SAr) ₂Pt(P2)]²⁺, characterized by a flexible {Pt ₂(μ-SAr)₂} square motif. The magnetic properties of the TCNQF₄^- salts of these bimetallic Pt(II) complexes are determined from susceptibility measurements and a tentative rationale for the formation of such {Pt₂(μ-SAr)₂} square complexes are provided, based on an original oxidative dimerization process.

Full text of DOI:10.1016/j.jorganchem.2012.07.001

Journal of Organometallic Chemistry 716 (2012) 237e244
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Oxidative access to flexible {Pt2(
m
-SAr)2} square motifs from platinum thiolato
complexes with chelating diphosphine
,
Su-Kyung Lee a, Olivier Jeannin b, Marc Fourmigué b, Wooyoung Suh a, Dong-Youn Noh a
*
a Department of Chemistry, Seoul Women’s University, Seoul 139-774, South Korea
b Institut des Sciences Chimiques de Rennes, Université de Rennes 1, UMR CNRS 6226, Rennes 35042, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Platinum(II) aryl thiolate complexes formulated as (P2)Pt(SAr)2 are prepared from the chelating bis(di-
phenylphosphino)dimethyltetrathiafulvalene (P2), with aryl thiolate ligands (SAr), such as benzene-
thiolate (BT) and 3,5-dimethylbenzenethiolate (DMBT). The structurally characterized neutral (P2)
Pt(SAr)2 complexes afford, upon oxidation with TCNQF4, dicationic bimetallic Pt(II) complexes formu-
Received 11 May 2012
Received in revised form
29 June 2012
Accepted 3 July 2012
lated as [(P2)Pt(
m m-SAr)2} square motif. The magnetic
-SAr)2Pt(P2)]2þ, characterized by a flexible {Pt2(
properties of the TCNQFꢀ4ꢁ salts of these bimetallic Pt(II) complexes are determined from susceptibility
Keywords:
Heteroleptic P2Pt(II)S2 complex
Aryl thiolate
measurements and a tentative rationale for the formation of such {Pt2(
provided, based on an original oxidative dimerization process.
m-SAr)2} square complexes are
Ó 2012 Elsevier B.V. All rights reserved.
{Pt2(m-SR)2} square motif
Oxidative dimerization
X-ray crystal structure
1. Introduction
Redox activity can also be observed on diphosphine ligand itself,
for example in ferrocene-based complexes (dppf)Pt(SR)2 (R ¼ Ph
[8], nPr [8], C6F5 [13], p-C6HF4 [7a]). However, in these complexes,
irreversible redox processes associated to the thiolate ligands were
observed before ferrocene oxidation. A combination of both redox
active dppf and dithiolene ligands was also reported, as in (dppf)
Pt(bdt) [14] (bdt: 1,2-benzenedithiolate) or (dppf)Pt(dmit) [7c]
(Scheme 2). In these complexes, two reversible oxidation waves
were observed, which were attributed to the oxidation of the
ferrocene core and the Pt(dithiolene) metallacycle, respectively.
Square-planar palladium(II) and platinum(II) complexes have
been intensively investigated for their structural diversity [1,2],
anticancer activity [3], catalytic effect [4] and photochemical prop-
erties [5], as well as their capacity to sustain reversible oxidation to
the radical state, toward the formation of conducting materials [6].
Mononuclear systems with {P2PtS2} coordination motifs are espe-
cially attractive in this respect, specifically those with chelating
dithiolate ligands or with redox active diphosphines such as 1,10-
bis(diphenylphosphino)ferrocene (dppf) [7,8] or 3,4-dimethyl-30,40-
bis(diphenylphosphino) tetrathiafulvalene (hereafter, abbreviated
as P2) [9e11]. Indeed, the 16-electron (diphosphine)Pt(dithiolene)
complexes, for example, (dppe)Pt(dmit) [12] (dmit: 2-thio-1,3-
dithiole-4,5-dithiolato; dppe: 1,2-bis(diphenylphosphino)ethane)
or (dppe)Pt(dddt) [10] (dddt: 4,5-dihydro-1,4-dithiine-2,3-
dithiolato) (Scheme 1), have shown reversible oxidation as the
cation radical state. This is attributed to the non-innocent character
of the dithiolene ligands.
Similarly,
in
tetrathiafulvalenyl-based
(P2)Pt(dithiolene)
complexes such as (P2)Pt(dmit) or (P2)Pt(dddt) (Scheme 3) [10,11], up
to four oxidation waves were identified, which were attributed to the
sequential oxidation of the independent redox moieties, namely the
TTF core on the one hand and the Pt(dddt) moiety on the other hand.
In this respect, it is of interest to investigate the corresponding
simple bis(monothiolate) derivatives, (P2)Pt(SR)2, in order to
determine their redox behavior and their capacity to form radical
species, compared to the corresponding dithiolene analogs. We
describe herein the preparation, structural and electronic proper-
ties of two (P2)Pt(SAr)2 complexes with different aryl thiolate (SAr)
ligands. Their oxidation with TCNQF4 led to unexpected dicationic
bimetallic [(P2)Pt(m
-SAr)2Pt(P2)]2þ complexes. The structure and
magnetic properties of these TCNQFꢀ4ꢁ radical salts are described
* Corresponding author. Tel.: þ82 2 970 5656; fax: þ82 2 970 5972.
E-mail address: dynoh@swu.ac.kr (D.-Y. Noh).
and a rationale is proposed for the formation of these flexible
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.07.001

238
S.-K. Lee et al. / Journal of Organometallic Chemistry 716 (2012) 237e244
Ph2
P
Ph2
P
Ph2
Ph2
S
S
S
S
S
S
S
S
S
S
S
S
P
S
S
P
S
S
S
S
S
S
Pt
Pt
Pt
P
Ph2
S
P
P
Ph2
P
Ph2
Ph2
P2
(P2)Pt(dddt)
(dppe)Pt(dddt)
(dppe)Pt(dmit)
Ph2
S
S
S
S
P
S
S
S
Scheme 1. (dppe)Pt(dithiolate) complexes.
Pt
S
P
S
Ph2
{Pt2S2} motifs, which are currently the subject of renewed interest
(P2)Pt(dmit)
because of their attractive flexibility and reactivity [15,16].
Scheme 3. P2 free ligand and (P2)Pt(dithiolate) complexes.
2. Results and discussion
2.1. Syntheses
assumption, we also investigated the electrochemical response of
the analogous dppe complexes described above, which lack the
redox active TTF core. As shown in Fig. 2, the oxidation of (dppe)
Pt(BT)2 clearly shows an irreversible wave at exactly the same
potential where the shoulder was found in the oxidation of (P2)
Pt(BT)2. We can tentatively conclude that the first irreversible
process is associated with thiolate oxidation, leaving a cationic
intermediate [(P2)Pt(BT)]þ species. The reversible oxidation
processes observed at higher potentials in (P2)Pt(BT)2 and (P2)
Pt(DMBT)2 (Fig. 1) are thus attributable to the TTF core oxidation,
shifted to more anodic potentials than is (P2)PtCl2 because of the
positive charge of the intermediate.
The thiolate (P2)Pt(SAr)2 complexes where SAr is benzene-
thiolate (BT), or 3,5-dimethylbenzenethiolate (DMBT), were
prepared as previously described for dithiolene complexes [10,11],
by the metathesis reaction of (P2)PtCl2 [9g] with the corresponding
arylthiols (ArSH) in the presence of NEt3 (Scheme 4). Purification by
column chromatography afforded the products in 60% yield. In
order to evaluate the respective role of the TTF core and the bis(-
thiolate)Pt moiety in the electrochemical properties of these
complexes, (dppe)Pt(BT)2 [17] and (dppe)Pt(DMBT)2 [18] were
prepared as described above. They were also obtained by another
route using lead thiolates [19], potentially a good alternative, since
the side-product (PbCl2) precipitates out from the reaction mixture
but reaction yields were disappointing (15%).
All of the platinum(II) complexes were characterized by spec-
troscopic methods such as FT-IR, NMR, UV/vis and/or MALDI-TOF
MS. Actually, in the mass spectra of the (P2)Pt(SAr)2 complexes,
the intensities for the Mþ peak are less than 1%, while those for
(Mþ ꢁ SAr) are 100%, indicating that the loss of one monothiolate
ligand to give a fragment of [(P2)Pt(SAr)]þ is favored under such
measurement conditions. This result contrasts strongly with those
described earlier for (P2)Pt(dithiolene) complexes incorporating
a chelating 1,2-dithiolate moiety, where the intensity of the
(Mþ þ 1) peak was reported to be 100% [10]. This behavior also
indicates that the bis(monothiolate) complexes described herein
are less stable than their corresponding dithiolate analogs, which is
a consequence of the absence of the chelate effect.
The oxidation of the (P2)Pt(SAr)2 complexes were also investi-
gated chemically by reacting them with TCNQF4, a well known
electron acceptor whose reduction potential to the TCNQFꢀ4ꢁ radical
anion (0.53 V vs SCE [20], z0.75 V vs Ag/AgCl) approximately
matches with the oxidation potential of the (P2)Pt(SAr)2 complexes
[21]. Mixing solution of the two compounds immediately afforded
a dark green colored solution from which crystals could be
obtained. X-ray crystal structure determinations (see below)
showed that the oxidation had indeed affected the electron-rich
thiolate ligands, since bimetallic dicationic species formulated as
[(P2)Pt(m
-SAr)2Pt(P2)]2þ were identified, which co-crystallized
with two TCNQFꢀ4ꢁ radical anions.
2.3. Structural properties
2.2. Electrochemical properties
Crystal structures could be obtained from X-ray diffraction on
single crystals for the two neutral complexes (P2)Pt(BT)2 and (P2)
Pt(DMBT)2, together with their TCNQF4 oxidation products. As
shown in Fig. 3, the coordination chemistry around the Pt atom in
(P2)Pt(BT)2 and (P2)Pt(DMBT)2 is close to square planar with
dihedral angles between the P2Pt and S2Pt mean planes of 8.04(3)ꢂ
and 6.86(3)ꢂ in (P2)Pt(DMBT)2 and (P2)Pt(BT)2, respectively.
Similarly, the TTF moiety is essentially planar, in contrast with other
P2-metal complexes where a stronger folding of the dithiole rings
along the S/S hinges has been reported [9]. The bond distances
and angles (Table 2) in the Pt coordination sphere are comparable
with those described for analogous complexes such as (dppe)
Pt(BT)2 [22], (dppv)Pt(BT)2 [23], (dppe)Pt(SeC6F5)2, or (dppe)
Pt(SeC6H4(o-CF3))2 [24].
The cyclic voltammograms of (P2)PtCl2, (P2)Pt(BT)2 and (P2)
Pt(DMBT)2 are compared in Fig. 1 and the numerical data are
collected in Table 1. While (P2)PtCl2 exhibits two reversible redox
waves upon oxidation, attributed to the redox behavior of TTF core
[9g], an additional shoulder is clearly identified at lower potentials
in the two aryl thiolate complexes, with an associated anodic shift
of the two following reversible waves. This behavior might indicate
the existence of a first oxidation process affecting the electron-rich
thiolate ligands before TTF oxidation itself. In order to test this
Ph2
P
Ph2
P
S
S
S
S
S
S
The oxidation of the complexes with TCNQF4 afforded two salts
incorporating the dicationic [(P2)Pt(m m-
-BT)2Pt(P2)]2þ and [(P2)Pt(
Pt
Fe
Pt
Fe
S
DMBT)2Pt(P2)]2þ species (Fig. 4). Since the BT-derivative is located
at an inversion center (Fig. 4a), the {Pt2S2} square metallacycle is
planar as shown in Fig. 5a. On the other hand, it adopts a butterfly
shape in the DMBT-derivative (Fig. 5b) with a folding angle
between the two PtS2 planes of 147.24(8)ꢂ. This difference between
P
P
Ph2
Ph2
(dppf)Pt(dmit)
(dppf)Pt(bdt)
Scheme 2. (dppf)Pt(dithiolate) complexes.

S.-K. Lee et al. / Journal of Organometallic Chemistry 716 (2012) 237e244
239
R
Ph2
P
Ph2
R
R
ArSH
S
S
S
S
P
S
S
S
S
S
S
PtCl2
Pt
CH2Cl2
P
P
Ph2
Ph2
(P2)PtCl2
(P2)Pt(SAr)2
R
S
SAr :
BT
DMBT
R = H R = Me
R
R
R
Ph2
P
Ph2
P
R
Pb(SAr)2
acetone
S
S
PtCl2
Pt
P
P
R
Ph2
Ph2
(dppe)PtCl2
(dppe)Pt(SAr)2
R
Scheme 4. Syntheses of (P2)Pt(SAr)2 and (dppe)Pt(SAr)2.
these two otherwise similar complexes illustrates the flexibility of
the {Pt2S2} core is hinged (Tables 3 and 4). The coordination around
the Pt atom is still very close to square-planar, with angles between
the PtS2 and PtP2 planes of 6.4(5)ꢂ in the BT-derivative and 6.0(9)
and 6.5(9)ꢂ in the DMBT-one.
these square motifs, as discussed below.
[(PeP)Pt(
usually have an anti conformation, R-groups pointing in opposite
directions, as in [(P2)Pt(
-BT)2Pt(P2)]2þ and other such compounds
m
-SR)2Pt(PeP)]2þ complexes with a planar {Pt2S2} core
m
The central C]C bond distance is a valuable indicator of the
oxidation state of the TTF as it adopts a short length in the reduced
form, while the lengthening of this bond accompanies the oxida-
tion of TTF, up to a full single bond character in the TTF2þ dication
[26]. The C]C bond distances in (P2)Pt(DMBT)2 and (P2)Pt(BT)2
amount to 1.351(6) and 1.334(7) Å, respectively. Turning to the
dicationic bimetallic species, these C]C bond distances are found
at comparable values, 1.343(8) Å in the centrosymmetric BT-
derivative and 1.337(16) and 1.351(16) Å in the DMBT-one. The
close proximity of these values clearly confirms that the TTF
moieties are not oxidized in these dicationic complexes. This
becomes more obvious if they are compared with the C]C bond
distances of the oxidized TTF moiety of a P2 radical cation, [(P2)
Mo(CO)4]2[Mo6O19] (1.388(5) Å) [27]. The dicationic charge in [(P2)
[15]. On the contrary, complexes with a hinged {Pt2S2} core domi-
nantly have a syn-exo conformation (R-groups on the same side)
[16d,24,25], possibly because the hinged {Pt2S2} core sterically
prefers the syn-exo conformation rather than the sterically unfa-
vored anti conformation. Therefore, to our knowledge, the [(P2)
Pt(m
-DMBT)2Pt(P2)]2þ complex with a hinged {Pt2S2} core is the
first compound that has an anti conformation. This sterically
unfavored conformation is allowed in this complex possibly due to
the comparatively bulky DMBT bridging and P2 terminal ligands.
The intramolecular Pt/Pt distance in the {Pt2S2} core is moderately
short (3.607(6) Å) in the BT-derivative and shorter in DMBT-
derivative (3.4562(7) Å) where the {Pt2S2} core is hinged along
the S/S axis. On the other hand, the intramolecular S/S distances
do not vary significantly (3.116(8) Å and 3.082(4) Å, respectively) as
Pt(m m
-BT)2Pt(P2)]2þ and [(P2)Pt( -DMBT)2Pt(P2)]2þ is therefore
concentrated on the {P2PtS2} core. Besides, since the redox process
involved the TCNQF4 as an oxidant (toward the thiolate ligand), the
latter is now reduced in its radical TCNQFꢀ4ꢁ anion form. This state is
unambiguously confirmed by several observations, (1) the averaged
distances of CeC (1.422(5) Å) and C]C (1.361(6) Å) bonds in the
quinone ring, and those of CeF (1.351(4) Å) and C^N (1.157(6) Å)
bonds in TCNQF4, (2) the IR n(C^N) stretching frequency observed
at 2192 cmꢁ1 compared to that of neutral TCNQF4 (2226 cmꢁ1), all
Table 1
Cyclic voltammetry data for the (P2)Pt complexes.a
b
b
Complex
E1pa
E2pa
E3pa
E2pc
E3pc
E21/2
E31/2
(P2)PtCl2
(P2)Pt(DMBT)2
(P2)Pt(BT)2
0.777
0.833
0.827
1.245
1.290
1.276
0.691
0.736
0.733
1.166
1.181
1.184
0.734
0.785
0.780
1.206
1.236
1.230
0.706
0.732
50 mV sꢁ1 scan rate; Supporting electrolyte: 0.1 M n-Bu4N$PF6; Working Elec-
trode: Pt disk; Counter electrode: Pt wire; Ref. electrode: Ag/AgCl; 1 mM samples in
CH2Cl2: E1/2 ¼ 0.565 V for Fcþ/Fc.
a
Fig. 1. The cyclic voltammograms of the (P2)Pt complexes measured in CH2Cl2 (Fc/
Fcþ ¼ 0.565 V vs Ag/AgCl).
b
E1/2 ¼ (Epa þ Epc)/2.

240
S.-K. Lee et al. / Journal of Organometallic Chemistry 716 (2012) 237e244
Table 2
Selected bond distances (Å) and angles (ꢂ) for (P2)Pt(BT)2 and (P2)Pt(DMBT)2.
(P2)Pt(BT)2
(P2)Pt(DMBT)2
PteP(1)
PteP(2)
PteS(5)
PteS(6)
S(5)eC(33)
S(6)eC(39)
P(1)ePteP(2)
P(1)ePteS(5)
P(2)ePteS(5)
P(1)ePteS(6)
P(2)ePteS(6)
S(5)ePteS(6)
2.2362(10)
2.2324(10)
2.3729(10)
2.3787(9)
1.762(4)
1.766(4)
88.63(4)
90.57(4)
PteP(1)
PteP(2)
PteS(5)
PteS(6)
S(5)eC(33)
S(6)eC(41)
P(1)ePteP(2)
P(1)ePteS(5)
P(2)ePteS(5)
P(1)ePteS(6)
P(2)ePteS(6)
S(5)ePteS(6)
2.2459(12)
2.2429(12)
2.3348(12)
2.3808(11)
1.780(5)
1.775(5)
87.92(4)
171.56(4)
100.43(4)
84.75(4)
169.22(4)
87.14(4)
174.36(3)
173.43(3)
86.51(3)
94.70(4)
temperature dependence of the magnetic susceptibility of both
salts was fitted within the singlet-triplet model (BleaneyeBowers)
with
Fig. 2. Comparison of cyclic voltammograms of (P2)Pt(BT)2 and (dppe)Pt(BT)2
measured in CH2Cl2 (Fc/Fcþ ¼ 0.565 V vs Ag/AgCl).
!
3Ng2b2
kT½3 þ expðꢁJ=kTÞꢃ
c
¼
c0 þ xcCurie
þ
1 ꢁ x
unambigously correspond to those of the TCNQFꢀ4ꢁ radical anion
[28,29].
where c0 is a temperature-independent contribution, x the fraction
of Curie-type magnetic defaults and J the magnetic coupling
interaction, giving c0(BT)
¼
5
ꢄ
10ꢁ5 cm3 molꢁ1
,
2.4. Magnetic properties in the solid state
c0(DMBT) ¼ 8.8 ꢄ 10ꢁ4 cm3 molꢁ1, xBT ¼ 0.058, xDMBT ¼ 0.046, J/
k(BT) ¼ ꢁ765(9) K (ꢁ532 cmꢁ1) and J/k(DMBT) ¼ ꢁ587(9) K
(ꢁ408 cmꢁ1).
The temperature dependence of the magnetic susceptibility of
both TCNQFꢀ4ꢁ salts (Fig. 6) show weak paramagnetism with the
susceptibility going through a rounded maximum, around room
temperature for the DMBT-salt and above room temperature for the
BT-salt. This behavior is characteristic of antiferromagnetic inter-
actions which settle between the TCNQFꢀ4ꢁ radical species.
Actually, the solid state arrangement in the BT-salt (Fig. 7) shows
that the TCNQFꢀ4ꢁ moieties are associated two-by-two and sand-
wiched between the planar TTF moieties in the P2 ligand. A similar
organization is also found for the DMBT-salt (Fig. 8), even though
the TTF moieties are also facing each other. The overlap interaction
between the TCNQFꢀ4ꢁ radical species is shown in Fig. 9. Of partic-
ular note is the short intermolecular C/C distances within these
dianionic dyads, which are as short as 3.166(10) Å in the BT-salt and
3.05(1) Å in the more distorted DMBT-salt. These very short
contacts allow for a strong interaction between the singly occupied
TCNQF4 LUMOs, leading to the formation of (fully filled) bonding
and (empty) antibonding combinations. Accordingly, the
3. Conclusions
We have shown here that the tetrathiafulvalenyl diphosphine
platinum bis(thiolate) complexes (P2)Pt(BT)2 and (P2)Pt(DMBT)2
exhibit a low potential irreversible oxidation wave not observed in
the (P2)PtCl2 complex. Based on the behavior of analogous (dppe)
Fig. 4. Molecular structures of (a) [(P2)Pt(
DMBT)2Pt(P2)]2þ in the form of their TCNQF4 salts.
m m-
-BT)2Pt(P2)]2þ and (b) [(P2)Pt(
Fig. 3. Molecular structures of (a) (P2)Pt(BT)2 and (b) (P2)Pt(DMBT)2.

S.-K. Lee et al. / Journal of Organometallic Chemistry 716 (2012) 237e244
241
Table 4
Selected bond distances (Å) and angles (ꢂ) in [(P2)Pt(
m
-DMBT)2Pt(P2)](TCNQF4)2.
Distance (Å)
Angle (ꢂ)
Pt(1)eP(1)
Pt(1)eP(2)
Pt(1)eS(5)
Pt(1)eS(6)
Pt(2)eP(3)
Pt(2)eP(4)
Pt(2)eS(5)
Pt(2)eS(6)
Pt(1)/Pt(2)
S(5)/S(6)
2.253(3)
2.264(3)
2.362(3)
2.374(3)
2.257(3)
2.263(3)
2.372(3)
2.375(3)
3.4562(7)
3.082(4)
P(1)ePt(1)eP(2)
P(2)ePt(1)eS(5)
P(1)ePt(1)eS(6)
S(5)ePt(1)eS(6)
P(3)ePt(2)eP(4)
P(3)ePt(2)eS(5)
P(4)ePt(2)eS(6)
S(5)ePt(2)eS(6)
Pt(1)eS(5)ePt(2)
Pt(1)eS(6)ePt(2)
86.11(10)
100.01(9)
92.81(10)
81.22(9)
87.83(10)
98.28(10)
92.91(9)
80.99(9)
93.79(9)
93.41(9)
Fig. 5. Geometries of {P2Pt(
(planar) and (b) [(P2)Pt(
-DMBT)2Pt(P2)]2þ (bent).
m-S)2PtP2} core observed in (a) [(P2)Pt(m
-BT)2Pt(P2)]2þ
m
Pt(BT)2 and (dppe)Pt(DMBT)2 complexes lacking the TFF redox core,
it was tentatively associated to thiolate oxidation. This was further
confirmed by the TCNQF4 oxidation of the two complexes, which
affords dicationic [(P2)Pt(m
-SAr)2Pt(P2)]2þ species. Their forma-
tions are associated with loss (and potential oxidation) of one thi-
olate ligand, as tentatively illustrated in Scheme 5, with the reduced
TCNQF4 radical anion precipitating as radical anion with the
dimerized dicationic species, [(P2)Pt(
It should be also emphasized here that this oxidative dimeriza-
tion mechanism for the formation of the {Pt2( -SAr)2} bimetallic
m .
-SAr)2Pt(P2)]2þ
room temperature with a CHI 620A Electrochemical Analyzer (CHI
Instrument Inc.) in 3 mL of CH2Cl2 solution containing 1 mM of the
sample, using 0.1 M n-Bu4N$PF6 as the supporting electrolyte, Ag/
AgCl as a reference electrode, a Pt button working electrode, a Pt
wire as the counter electrode and with a scan rate of 50 mV sꢁ1. All
redox potentials were referenced against the Fcþ/Fc redox couple
(E1/2 ¼ 0.565 V). The magnetic susceptibility measurements were
obtained with the use of a Quantum Design SQUID magnetometer
MPMS-XL. This magnetometer works between 1.8 and 400 K for DC
applied fields ranging from ꢁ5 to 5 T. The measurements were
performed at 5 kG on polycrystalline TCNQF4 salts of the BT
(3.2 mg) and DMBT (6.3 mg). The magnetic data were corrected for
the sample holder and the diamagnetic contributions.
m
square motif complements the other previously described
methods, which involved (i) the alkylation of a pre-formed {Pt2S2}
motif [15], (ii) the in situ combination (metathesis) of (PeP)Pt and
bridging thiolate ligand [25], (iii) the nucleophilic displacement
(metathesis) of the triflate leaving group by a pre-formed (PeP)
Pt(SR)2 complex [24], and (iv) the ring-opening of the thiaplatina-
cycle [30]. It provides a potential better approach to the synthesis of
such bimetallic complexes particularly adapted to electron-rich
thiolate ligands, but whose promise has yet to be demonstrated
with other diphosphines than P2.
The crystallographic determinations of the two bimetallic
compounds, [(P2)Pt(m m ,
-BT)2Pt(P2)]2þ and [(P2)Pt( -DMBT)2Pt(P2)]2þ
4.2. Preparation of (P2)Pt(SAr)2 complexes
give also two other examples of structural flexibility in such bimetallic
systems incorporating the {Pt2S2} square motif with bridging RSꢁ and/
or S2ꢁ ligands [15,16].
A CH2Cl2 solution (25 mL) of (P2)PtCl2 (0.2 mmol, 173 mg), trie-
thylamine (0.8 mmol, 81 mg) and aryl thiol (0.4 mmol, 55 mg) for
3,5-dimethylbenzenethiol (DMBT-H) 44 mg for benzenethiol (BT-H)
was stirred for 24 h at room temperature under an argon atmo-
sphere. The red-orange solution was evaporated and the solid
residue was purified by column chromatography (SiO2, CH2Cl2). The
red-orange products were recrystallized from CH2Cl2/MeOH.
(P2)Pt(BT)2. Yield: 69% (140 mg); m.p. >275 ꢂC (decomp.); 1H
4. Experimental
4.1. General procedures
First grade organic solvents were purchased and used without
further purification. They were degassed by bubbling Ar prior to
use. All reactions and recrystallizations involving Pt(II) complexes
were carried out under protection from light and air. The starting Pt
complex (P2)PtCl2 was prepared as previously described [9g] from
P2 [9a]. The melting points were determined using a Stuart SMP3
(Barloworld Scientific Ltd.). The MALDI-TOF mass spectra were
measured with a Voyager-DEÔ STR Biospectrometry Workstation
(Applied Biosystems Inc.). The infrared spectra were recorded by
the KBr pellet method on a Perkin Elmer Spectrum 100 in the range
of 4000e400 cmꢁ1. The 1H/31P NMR measurements were per-
formed at room temperature using an Avance 500 (Bruker,
500 MHz) with the samples dissolved in CDCl3. The positive
chemical shifts are reported downfield from the external standards,
viz. 85% H3PO4 for the 31P{1H} resonances. The UV/vis spectra were
obtained on an HP 8452A diode array spectrophotometer in CH2Cl2.
The cyclic voltammetry (CV) measurements were carried out at
NMR (300 MHz, CDCl3, TMS):
7.02 (m, 4H, CH in BT), 6.70 (m, 6H, CH in BT),1.87 ppm (s, 6H, CH3 in
d
¼ 7.76 (m, 8H, Ph), 7.47 (m, 12H, Ph),
Table 3
Selected bond distances (Å) and angles (ꢂ) in [(P2)Pt(
m-BT)2Pt(P2)](TCNQF4)2.
Distance (Å)
Angle (ꢂ)
Pt(1)eP(1)
Pt(1)eP(2)
Pt(1)eS(5)
Pt(1)eS(5)i
Pt(1)/Pt(1)i
S(5)/S(5)i
2.2766(9)
2.2548(10)
2.3784(9)
2.3879(9)
3.607(6)
P(1)ePt(1)eP(2)
P(2)ePt(1)eS(5)i
S(5)ePt(1)eS(5)
P(1)ePt(1)eS(5)
P(2)ePt(1)eS(5)i
Pt(1)eS(5)ePt(1)i
87.19(3)
94.09(3)
81.64(3)
97.39(3)
94.09(3)
98.36(3)
Fig. 6. Temperature dependence of the magnetic susceptibility for [(P2)Pt(
BT)2Pt(P2)]2þ[(TCNQF4)2]2ꢁ and [(P2)Pt( -DMBT)2Pt(P2)]2þ[(TCNQF4)2]2ꢁ. Solid lines
are fits to the singlet-triplet model (see text).
m-
3.116(8)
m
i
Symmetry code: ꢁx, ꢁy, ꢁz.

242
S.-K. Lee et al. / Journal of Organometallic Chemistry 716 (2012) 237e244
Fig. 7. View of the solid state organization within one layer in [(P2)Pt(m
-BT)2Pt(P2)][(TCNQF4)2], with [(TCNQF4)2]2ꢁ dimers sandwiched between the TTF moieties. Solvent
molecules and hydrogen atoms were omitted for clarity.
Fig. 8. View of the solid state organization within one layer in [(P2)Pt(m
-DMBT)2Pt(P2)][(TCNQF4)2], with [(TCNQF4)2]2ꢁ dimers sandwiched between the TTF moieties. Solvent
molecules and hydrogen atoms were omitted for clarity.
TTF); 31P NMR (121 MHz, CDCl3, 85% H3PO4):
d
¼ 31.99 ppm
(JPteP ¼ 2862 Hz); FT-IR (KBr): 3058 (Ar CeH), 2989, 2913 (eCH3),
1577, 1480, 1469, 1434 (Ar C]C), 1101, 1085 (PePh), 1023, 1008,
998 (Ar CeH ip def), 882 (asym SeCeS), 731, 686 (Ar CeH oop def)
548, 520, 484 cmꢁ1 (Ar ring oop def); UV/vis (CH2Cl2): lmax ¼ 232 (s),
276 (m), 340 (sh), 420 nm (w); MALDI-TOF MS: m/z (%) 1012.8970 (1)
[Mþ]; 904.9208 (100) [Mþ ꢁ SC6H5]. EA calcd for C44H36P2PtS6 (MW:
1013.14 g/mol): C 52.12; H 3.58%. Found: C 51.92; H 3.62%.
(P2)Pt(DMBT)2. Yield: 62% (133 mg); m.p. 256e257 ꢂC; 1H NMR
(500 MHz, CDCl3, TMS):
d
¼ 7.72 (m, 8H, Ph), 7.46 (t, 4H, Ph), 7.39
(t, 8H, Ph), 6.64 (s, 4H, CH in DMBT), 6.32 (s, 2H, CH in DMBT), 1.88
(s, 12H, CH3 in DMBT), 1.86 ppm (s, 6H, CH3 in TTF); 31P NMR
(202 MHz, CDCl3, 85% H3PO4):
d
¼ 32.12 ppm (JPteP ¼ 2888 Hz);
FT-IR (KBr): 3049, 3020 (Ar CeH), 2912, 2853 (eCH3), 1594,
1574, 1480, 1434 (Ar C]C), 1099 (PePh), 1027, 1008, 999 (Ar CeH
ip def), 839 (asym SeCeS), 744, 689 (Ar CeH oop def), 546, 519,
480 cmꢁ1 (Ar ring oop def); UV/vis (CH2Cl2): lmax ¼ 232 (s), 276
(m), 340 (sh), 420 nm (w); MALDI-TOF MS: m/z (%) 1068.9532 (1)
[Mþ], 932.9751 (100) [Mþ ꢁ SC6H3Me2]. EA calcd for C48H44P2PtS6
(MW: 1069.20 g/mol): C 53.87; H 4.15%. Found: C 53.69; H 4.20%.
Fig. 9. Overlap modes of TCNQF4 observed in [(P2)Pt(m
-SAr)2Pt(P2)]2þ[(TCNQF4)2]2ꢁ
where SAr is (a) BT and (b) DMBT.

S.-K. Lee et al. / Journal of Organometallic Chemistry 716 (2012) 237e244
243
Ar
4.22. Found: C, 55.27; H, 4.20%. Inclusion of one water molecule
gives calculated values for C38H34P2PtS2$H2O: C, 55.00; H, 4.37,
which is in good accordance with the experimental values.
(dppe)Pt(DMBT)2. Yield: 15% (12.6 mg); m.p. >160 ꢂC (decomp);
Ar
Ph2
P
Ph2
P
S
S
S
S
S
S
S
S
S
S
Pt
Pt
S
P
P
1H NMR (300 MHz, CDCl3, TMS):
d
¼ 7.66 (m, 8H, Ph), 7.33 (m, 12H,
Ph2
Ph2
Ar
(P2)Pt(SAr)2
S-Ar
TCNQF4
Ph), 6.71 (s, 4H, CH in DMBT), 6.31 (s, 2H, CH in DMBT), 2.21 (s, 4H,
PCH2CH2P), 1.86 ppm (s, 12H, CH3 in DMBT); 31P NMR (121 MHz,
TCNQF4
Ph2
CDCl3, 85% H3PO4):
d
¼ 46.26 ppm (JPteP ¼ 2951 Hz); FT-IR (KBr):
3051, 3021 (Ar CeH), 2914, 2856 (eCH3), 1595, 1575, 1464, 1434 (Ar
C]C), 1104 (PePh), 1028, 998 (Ar CeH ip def), 840 (asym SeCeS),
747, 75, 689 (Ar CeH oop def), 532, 486 cmꢁ1 (Ar ring oop def); UV/
vis (CH2Cl2): lmax ¼ 230 (s), 260 nm (sh). EA calcd for C42H42P2PtS2
(MW: 867.96 g/mol): C 58.12; H 4.88%. Found: C 57.95; H 4.75%.
ArS-SAr
Ar
Ph2
P
2+
S
S
S
S
S
P
S
S
S
Pt
Pt
P
S
P
S
Ph2
Ph2
Ar
4.4. Preparation of TCNQF4 salts
2+
µ
[(P2)Pt( -SAr)2Pt(P2)]
[(P2)Pt(m-BT)2Pt(P2)](TCNQF4)2$(PhCl)4. To a chlorobenzene
Scheme 5. The proposed dimerization process to the [(P2)Pt(m
-SAr)2Pt(P2)]2þ dication.
solution (1 mL) of (P2)Pt(BT)2 (0.01 mmol, 10 mg) was added
a chlorobenzene solution (1 mL) of TCNQF4 (0.01 mmol, 2.8 mg).
The dark green solution was heated at 70 ꢂC for 40 min. Some black
crystals began to form, as the reaction solution was stored in
a freezer. The product was filtered off, washed with cold chloro-
benzene and dried under vacuum.
4.3. Preparation of (dppe)Pt(SAr)2 complexes
An acetone solution (5 mL) of Pb(SAr)2 [19] (0.1 mmol,
SAr ¼ DMBT (48 mg) and BT (43 mg)) was added to an acetone
suspension (5 mL) of (dppe)PtCl2 (0.1 mmol, 66 mg) with stirring
for 24 h at room temperature. The PbCl2 precipitate was separated
by filtration and the purified product was recrystallized from
acetone/pentane.
FT-IR (KBr): 2192, 2170 cmꢁ1 (C^N). EA calcd for
C124H82Cl4F8N8P4Pt2S10 (MW: 2812.52 g/mol): C 52.92; H 2.94; N
3.99; Found: C 52.68; H 3.10; N 4.74.
[(P2)Pt(m-DMBT)2Pt(P2)](TCNQF4)2$(PhCH3)(CHCl3)3. To a toluene
solution (0.8 mL) of (P2)Pt(DMBT)2 (0.01 mmol, 11 mg) was added
a CHCl3 (1.3 mL) and toluene solution (0.2 mL) of TCNQF4 (0.01 mmol,
3 mg). The dark green solution was heated at 55 ꢂC for 40 min. Some
black crystals began to form as the reaction solution cooled down to
room temperature and the solution was then stored in a freezer. The
product was filtered off, washed with cold chlorobenzene and dried
under vacuum.
(dppe)Pt(BT)2. Yield: 15% (12.0 mg); m.p. >188 ꢂC (decomp); 1H
NMR (300 MHz, CDCl3, TMS):
7.05 (m, 4H, CH in BT), 6.61 (m, 6H, CH in BT), 2.18 ppm (s, 4H,
PCH2CH2P); 31P NMR (121 MHz, CDCl3, 85% H3PO4):
d
¼ 7.65 (m, 8H, Ph), 7.36 (m, 12H, Ph),
d
¼ 45.78 ppm
(JPteP ¼ 2880 Hz); FT-IR (KBr): 3051 (Ar CeH), 1577, 1484, 1471, 1435
(Ar C]C), 1102, 1085 (PePh), 1025, 998 (Ar CeH ip def), 880 (asym
SeCeS), 749, 735, 689 (Ar CeH oop def) 530, 486 cmꢁ1 (Ar ring oop
def); UV/vis (CH2Cl2): lmax ¼ 232 (s), 262 (m), 360 nm (w). EA calcd
for C38H34P2PtS2 (MW: 811.24 g/mol): C38H34P2PtS2 C, 56.22; H,
FT-IR (KBr): 2192, 2170 cmꢁ1 (C^N). EA calcd for
C114H81Cl9F8N8P4Pt2S10 (MW: 2866.50 g/mol): C 47.73; H 2.85; N
3.91. Found: C 48.09; H 2.53; N 4.03.
Table 5
Crystal data and structure refinement parameters for platinum(II) complexes.
(P2)Pt(DMBT)2
(P2)Pt(BT)2
[(P2)Pt(
m
-BT)2Pt(P2)]
[(P2)Pt(m-DMBT)2Pt(P2)]
(TCNQF4)2$4PhCl
(TCNQF4)2$MePh$3CHCl3
Formula
C48H44P2PtS6
1070.22
Monoclinic
P21/c
9.0616(5)
23.8498(15)
20.7935(14)
90.00
94.005(2)
90.00
C44H36P2PtS6
1014.12
Monoclinic
P21/n
16.0528(6)
15.9253(6)
17.3584(7)
90.00
110.567(2)
90.00
C124H82Cl4F8N8P4Pt2S10
2812.52
Triclinic
Pꢁ1
C114H81Cl9F8N8P4Pt2S10
2868.58
Monoclinic
P21/n
15.0588(11)
20.2005(13)
38.277(3)
90.00
92.896(2)
90.00
Formula weight
Crystal system
Space group
a (Å)
14.0911(11)
14.6513(10)
14.7880(11)
80.652(4)
72.806(4)
82.403(4)
2866.0(4)
1
b (Å)
c (Å)
a
b
g
(ꢂ)
(ꢂ)
(ꢂ)
Volume (Å3)
Z
4482.9(5)
4
1.586
4154.8(3)
4
1.621
11628.8(14)
4
1.638
Dcal (Mg/m3)
1.630
2.837
m
(mmꢁ1
)
3.515
3.788
2.910
F(000)
Cryst. size (mm3)
range (ꢂ)
2144
2016
1398
5688
0.5 ꢄ 0.3 ꢄ 0.2
1.30e27.47
ꢁ11 ꢅ h ꢅ 7
ꢁ30 ꢅ k ꢅ 30
ꢁ26 ꢅ l ꢅ 26
0.293, 0.495
10,245/0/520
1.084
0.3 ꢄ 0.2 ꢄ 0.1
1.49e27.46
ꢁ16 ꢅ h ꢅ 20
ꢁ20 ꢅ k ꢅ 20
ꢁ22 ꢅ l ꢅ 18
0.419, 0.685
9496/0/480
1.128
0.3 ꢄ 0.1 ꢄ 0.05
2.42e27.55
ꢁ18 ꢅ h ꢅ 18
ꢁ18 ꢅ k ꢅ 18
ꢁ19 ꢅ l ꢅ 17
0.719, 0.868
12,654/68/787
1.188
0.1 ꢄ 0.06 ꢄ 0.01
1.07e27.54
ꢁ19 ꢅ h ꢅ 19
ꢁ18 ꢅ k ꢅ 26
ꢁ49 ꢅ l ꢅ 49
0.811, 0.971
26,785/0/1392
1.074
q
Index ranges
Tmin, Tmax
Data/restr./param.
GOF
wR(F2) [all data]
R(F) [I > 2sigma(I)]
Res. dens. (e/Å3)
0.1068
0.0311
ꢁ1.06, 1.01
0.0956
0.0316
ꢁ1.74, 0.79
0.0982
0.0301
ꢁ1.84, 2.93
0.1613
0.0716
ꢁ2.14, 2.44

244
S.-K. Lee et al. / Journal of Organometallic Chemistry 716 (2012) 237e244
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The experimental data and refinement results are given in
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diffractometer with Mo-K
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the structure factor calculation but not refined. [(P2)Pt(m-
BT)2Pt(P2)](TCNQF4)2 crystallizes with four PhCl solvent molecules,
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Acknowledgments
This French-Korean collaborative work was supported by the
bilateral STAR program under the reference numbers 19036SM and
12974RC, as well as by the CNRS (France) and the University Rennes
1 through the GDRI program “Functional Material for Organic
Optics, Electronics, and Devices” (FUN MOOD). Work at Seoul
Women’s University was supported by Basic Science Research
Program through the National Research Foundation of Korea (NRF)
funded by the Ministry of Education, Science and Technology
(NRF2010-0011478). We thank CDIFX (Rennes) for access to X-ray
diffractometers for X-ray data collections.
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Appendix A. Supplementary material
CCDC 826353e826356 contains the supplementary crystallo-
graphic data for (P2)Pt(BT)2, (P2)Pt(DMBT)2, [(P2)Pt(
DMBT)2Pt(P2)](TCNQF4)2$MePh$3CHCl3 and [(P2)Pt(
m
m
-
-
(b) M.E. Peach, Can. J. Chem. 46 (1968) 2699e2706.
BT)2Pt(P2)](TCNQF4)2$4PhCl, respectively. These data can be
obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.
html or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK [fax: þ44 1223/336 033.
E-mail: deposit@ccdc.cam.ac.uk].
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