Syntheses and characterization of heterobimetallic complexes (dppf)Pt(dithiolate) (dppf: bis(diphenylphosphino)ferrocene); X-ray crystal structures of (dppf)PtL where L = dmit, phdt and i-mnt

Article abstract of DOI:10.1016/S0277-5387(01)00783-5

Hetrobimetallic complexes of the type (dppf)PtL (dppf = 1,1′-bis(diphenylphosphino)ferrocene; L = dmit (1,3-dithiole-2-thione-4,5-dithiolate), dddt (5,6-dihydro-1,4-dithiin-2,3-dithiolate), phdt (6-hydro-5-phenyl-1,4-dithiin-2,3-dithiolate), dphdt (5,6-diphenyl-1,4-dithiin-2,3-dithiolate), mtdt (1,2-bis(methylthio)ethylene-1,2-dithiolate), i-mnt (2,2-dicyano-1,1-ethylenedithiolate)) have been synthesized and studied by a high-resolution FAB-MS, cyclic voltammetry and ³¹P NMR. (Dppf)Pt(i-mnt) exhibits one reversible redox peak at E_1/2 = 1.225 V and a strong Pt-P coupling constant (J_Pt-P = 3237 Hz) due to the electron-accepting property of i-mnt ligand. On the contrary, (dppf)Pt(mtdt) shows three reversible redox peaks corresponding to [dppf]^0/+ (E_1/2¹ = 0.470 V), [Pt(mtdt)]^0/+ (E_1/2² = 1.050 V) and [Pt(mtdt)]^+/2+ (E_1/2³ = 1.405 V) processes and a weak Pt-P coupling constant (J_Pt-P = 2962 Hz) due to relatively strong electron-donor property of mtdt ligand. X-ray structural analyses were performed for the three complexes: (dppf)PtL where L = dmit, phdt and i-mnt. The P₂PtS₂ core shows a distorted square planar geometry for the three complexes with P(1)-Pt-P(2) bite angle being larger than 96°. The S(1)-Pt-S(2) bite angle of the i-mnt complex is the smallest (74.42°) because of the formation of the four-membered ring.

Full text of DOI:10.1016/S0277-5387(01)00783-5

Polyhedron 20 (2001) 1939–1945
www.elsevier.com/locate/poly
Syntheses and characterization of heterobimetallic complexes
(dppf)Pt(dithiolate) (dppf: bis(diphenylphosphino)ferrocene); X-ray
crystal structures of (dppf)PtL where L=dmit, phdt and i-mnt
Dong-Youn Noh a,*, Eun-Me Seo a, Ha-Jin Lee a, Hong-Young Jang b,
Moon-Gun Choi b, Young Hwan Kim c, Jongki Hong c
a Department of Chemistry, Seoul Women’s Uni6ersity, Seoul 139-774, South Korea
b Department of Chemistry, Yonsei Uni6ersity, Seoul 120-749, South Korea
c Mass Spectrometry Analysis Group, Korea Basic Science Institute, Taejon 305-333, South Korea
Received 18 December 2000; accepted 9 March 2001
Abstract
Heterobimetallic complexes of the type (dppf)PtL (dppf=1,1%-bis(diphenylphosphino)ferrocene; L=dmit (1,3-dithiole-2-thione-
4,5-dithiolate), dddt (5,6-dihydro-1,4-dithiin-2,3-dithiolate), phdt (6-hydro-5-phenyl-1,4-dithiin-2,3-dithiolate), dphdt (5,6-
diphenyl-1,4-dithiin-2,3-dithiolate), mtdt (1,2-bis(methylthio)ethylene-1,2-dithiolate), i-mnt (2,2-dicyano-1,1-ethylenedithiolate))
have been synthesized and studied by a high-resolution FAB-MS, cyclic voltammetry and 31P NMR. (Dppf)Pt(i-mnt) exhibits one
reversible redox peak at E1/2=1.225 V and a strong Pt–P coupling constant (JPt–P=3237 Hz) due to the electron-accepting
property of i-mnt ligand. On the contrary, (dppf)Pt(mtdt) shows three reversible redox peaks corresponding to [dppf]0/+
(E11/2=0.470 V), [Pt(mtdt)]0/+ (E12/2=1.050 V) and [Pt(mtdt)]+/2+ (E13/2=1.405 V) processes and a weak Pt–P coupling constant
(JPt–P=2962 Hz) due to relatively strong electron-donor property of mtdt ligand. X-ray structural analyses were performed for
the three complexes: (dppf)PtL where L=dmit, phdt and i-mnt. The P2PtS2 core shows a distorted square planar geometry for
the three complexes with P(1)–Pt–P(2) bite angle being larger than 96°. The S(1)–Pt–S(2) bite angle of the i-mnt complex is the
smallest (74.42°) because of the formation of the four-membered ring. © 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Pt(II); Dithiolate; Dppf; X-ray crystal structures; Cyclic voltammetry; 31P NMR
I [2,5–7]. Some variations of these complexes have been
reported, among which chloride ions are replaced by
1. Introduction
Since the discovery of ferrocene (di(h5-cyclopentadi-
the dithiolate ligand to obtain (phosphine)2M-
(dithiolate) complexes [8–10]. They were studied in the
enyl)iron: Fe(C5H5)2: Fc) [1], the cylindrical molecule
light of charge-transfer property, coordination chem-
with electron-rich aromatic systems has been widely
istry and the development of water-soluble phosphine
used in the development of catalyst, conducting/optical
material, molecular magnet, liquid crystal and polymer
because it shows the reversible redox behaviour [2]. One
of the representative ligand containing ferrocene is 1,1%-
complex.
Here, we report the syntheses of new heterobimetallic
(dppf)Pt(dithiolate) complexes where dithiolate ligands
are 1,3-dithiole-2-thione-4,5-dithiolate (dmit), 5,6-dihy-
bis(diphenylphosphino)ferrocene (dppf) [2–4] which is
dro-1,4-dithiin-2,3-dithiolate (dddt), 6-hydro-5-phenyl-
frequently utilized as a bidentate ligand in the design of
1,4-dithiin-2,3-dithiolate
(phdt),
5,6-diphenyl-1,4-
catalyst such as (dppf)MX2 heterobimetallic complex
dithiin-2,3-dithiolate (dphdt), 1,2-bis(methylthio)-1,2-
ethylenedithiolate (mtdt) and 2,2-dicyano-1,1-ethylene-
dithiolate (i-mnt), along with a facile synthetic way of
(dppf)PtCl2 in the three-components solvent system.
Chemical properties of [(dppf)Pt] unit are sensitive to
where M=Ni, Pd, Pt, Co, Zn, Cd, Hg and X=Cl, Br,
* Corresponding author. Tel.: +82-2-9705656; fax: +82-2-
9705660.
E-mail address: dynoh@swu.ac.kr (D.-Y. Noh).
0277-5387/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(01)00783-5

1940
D.-Y. Noh et al. / Polyhedron 20 (2001) 1939–1945
Bruker AXS SMART diffractometer equipped with
,
CCD area detector and Mo Ka (u=0.71073 A) radia-
tion, and centered in the beam at 293(2) K. The struc-
tures were solved and refined with the SHELX-97 [11]
using direct method and expanded using Fourier tech-
niques. All non-hydrogen atoms were refined anisotrop-
ically and hydrogens isotropically.
Scheme 1. Dithiolate ligand precursors.
2.3. Synthesis
the dithiolate ligand, which is studied by means of 31P
NMR and cyclic voltammetry. The crystal structures of
(dppf)PtL (L=dmit, phdt, i-mnt) are elucidated and
compared each other.
Nitrogen bubbling with heating was performed prior
to use degassed solvent water. Dithiolate ligand precur-
sors (4,5-dimethylthio-1,3-dithiole-2-one (DMT–DTO)
[12],
4,5-ethylenedithio-1,3-dithiole-2-one
(EDT–
DTO) [13], 4,5-phenylethylenedithio-1,3-dithiole-2-one
(PhEDT–DTO) [14], 4,5-diphenyl-ethylenedithio-1,3-
dithiole-2-one (dPhEDT–DTO) [14] (Scheme 1),
Na2(dmit) [13] and K2(i-mnt) [15] (Scheme 2) were
prepared under a dry nitrogen condition according to
the literature procedures. All reactions and recrystal-
lizations involving platinum complex were carried out
under the protection from light and air.
2. Experimental
2.1. Instrumentation
Melting points were determined using an electrother-
mal digital melting point apparatus IA9100 without
calibration. The normal FAB mass spectra were taken
with the first of the two mass spectrometers of a
JMS-HX110/110A tandem mass spectrometer (JEOL,
Tokyo, Japan) with mass resolution of 1000 (10% val-
ley) using a JMS-DA 9000 data system. 31P NMR
spectra were obtained on Varian Unity plus 300 spec-
trometer using H3PO4 as an external reference, infrared
spectra by KBr pellet method on MIDAC FT-IR spec-
trometer, UV–Vis spectra in acetonitrile on HP 8452A
diode array spectrometer. Cyclic voltammetry measure-
ments were carried out at room temperature with an
EG&G VersaStat model potentiostat/galvanostat in 10
ml CH2Cl2 solution containing 0.1 M n-Bu4N·BF4 as
electrolyte, Ag/Ag+ as a reference electrode, Pt-button
working electrode, platinum wire as a counter electrode
and a 0.05 V s−1 scan rate (E1/2=0.705 V for Fc/Fc+
couple).
2.3.1. (dppf )PtCl2
To a 12 ml ethanol suspension of K2PtCl4 (0.5 mmol,
21 mg) was added minimum amount of water until the
suspension becomes clear. A 12 ml benzene solution of
dppf (0.5 mmol, 28 mg) was slowly dropped to this
solution with continuous stirring for 12 h. The yellow
product was filtered and washed with distilled water
and MeOH, and recrystallized from CH2Cl2+MeOH.
Yield 93%; M.p. 305°C (dec.); HR-FABMS Calc. for
C34H28P2Cl2PtFe 820.0035. Found 820.0062 (M+); FT-
IR (KBr, cm−1) 3077, 3054 (Ar C–H), 1620, 1481,
1435 (Ar, CꢀC), 1387, 1308, 1264, 1171, 1096, 1038,
999, 824, 747, 694 (Ar, C–H), 640, 563, 519, 496, 471,
448 (ring-tilt and Fe–Cp in Fc); UV (CH3CN, nm)
218(st), 268(sh), 432(w).
2.2. X-ray data collection and structure determination
2.3.2. (dppf )Pt(dmit)
To a 5 ml ethanol solution of Na2dmit (0.11 mmol,
27 mg) was slowly added a 5 ml CHCl3 solution of
(dppf)PtCl2 (0.1 mmol, 82 mg). The yellow product
Single crystals suitable for X-ray diffraction study
were mounted on a glass capillary, transferred to a
Scheme 2. Synthesis of platinum complexes.

D.-Y. Noh et al. / Polyhedron 20 (2001) 1939–1945
1941
2.3.4. (dppf )Pt(i-mnt)
obtained after 1 h stirring was filtered and washed with
distilled water and MeOH, and recrystallized from
CHCl3+MeOH. Yield 91%; M.p. 218ꢀ220°C (dec.);
FABMS (m/z) 945.65 (M+); FT-IR(KBr, cm−1) 3052
(Ar, C–H), 1636, 1462, 1435 (Ar, CꢀC), 1387, 1306,
1262, 1167, 1096, 1053, 1032 (CꢀS), 997, 911, 845, 814,
745, 693 (Ar, C–H), 637, 554, 517, 492, 471, 438, 417
(ring-tilt and Fe–Cp in Fc); UV (CH3CN, nm) 212(st),
268(sh), 312(w), 466(w).
This was prepared following the procedure for
(dppf)Pt(dddt) by using excess K2(i-mnt) (0.2 mmol, 44
mg) instead of K2(dddt). Yield 90%; m.p. 217ꢀ220°C
(dec.); HR-FABMS Calc. for C38H29P2N2PtFeS2
890.0249. Found 890.0245 (M+); FT-IR (KBr, cm−1
)
3057 (Ar, C–H), 2209 (CꢁN), 1630, 1481, 1439 (Ar,
CꢀC), 1385, 1308, 1169, 1098, 1026, 997, 926, 889, 824,
748, 696 (Ar, C–H), 637, 559, 515, 494, 473, 440
(ring-tilt and Fe–Cp in Fc); UV (CH3CN, nm) 214(st),
274(sh), 340(m), 432(w).
2.3.3. (dppf )PtL (L=dddt, phdt, dphdt and mtdt)
Dddt complex was prepared as follows: to a 5 ml
ethanol suspension of EDT-DTO (0.11 mmol, 23 mg)
was added KOH (0.22 mmol, 12 mg) with stirring until
it dissolved completely by forming K2(dddt), and then a
5 ml CHCl3 solution of (dppf)PtCl2 (0.1 mmol, 82 mg).
This solution turned to orange colour immediately and
yellow precipitate was formed after stirring for 3 h. The
yellow product was filtered and washed with distilled
water and MeOH, and recrystallized from CH2Cl2+
MeOH. Phdt, dphdt and mtdt complexes were also
prepared by using an equimolar amount of PhEDT–
DTO, dPhEDT–DTO and DMT–DTO, respectively,
instead of EDT–DTO.
(dppf)Pt(dddt): yield 86%; m.p. 221ꢀ223°C (dec.);
HR-FABMS Calc. for C38H32P2PtFeS4 929.9866.
Found 929.9865 (M+); FT-IR (KBr, cm−1) 3050 (Ar,
C–H), 2913 (–CH2), 1636, 1480, 1435 (Ar, CꢀC), 1385,
1306, 1165, 1096, 1028, 999, 920, 884, 849, 820, 745,
694 (Ar, C–H), 637, 554, 515, 494, 469, 440 (ring-tilt
and Fe–Cp in Fc); UV (CH3CN, nm) 220(st), 246(sh),
316(w), 448(w).
3. Results and discussion
3.1. Synthesis and IR/UV–Vis/FABMS analysis
(dppf)PtCl2 was synthesized in three-solvent system
(ethanol:water:benzene=1:1:1, v/v) by stirring the reac-
tion mixture for 12 h at room temperature without
exposure to air and light (Scheme 2). This is a much
more facile way of preparing (dppf)PtCl2 compared to
the previous method [6,7] in which a benzene solution
of dppf suspended with PtCl2 was refluxed for 20 h.
The yield is 93% for the two cases. (dppf)PtL complexes
were easily prepared by mixing (dppf)PtCl2 prepared
thereby and the corresponding dithiolates (Scheme 2) in
chloroform via a salt elimination process. The elemen-
tal compositions of these complexes were identified by
the high-resolution FAB mass measurements except
dmit and dphdt complexes that showed relatively low
abundance of the molecular ion peaks in the normal
FAB mass spectra. In all of the FAB mass spectra
measured in this study, the peak at m/z 749 corre-
sponding to [(dppf)Pt]+ ion was detected as one of the
major peaks.
Infrared spectra of the platinum complexes exhibit
w(ring-tilt and Fe–Cp in Fc) at 555ꢀ440 cm−1 in
common. The characteristic vibrational peaks origi-
nated from the dithiolate ligands are also observed for
each complexes: w(CꢀS) at 1053 and 1032 cm−1 for
(dppf)Pt(dmit); w(–CH2) at 2913 and 2907 cm−1 for
(dppf)Pt(dddt) and (dppf)Pt(phdt), respectively; w(–
CH3) at 2976 cm−1 for (dppf)Pt(mtdt); w(CꢁN) at 2208
cm−1 for (dppf)Pt(i-mnt). UV–Vis spectra of
(dppf)PtL show a weak band at 432ꢀ450 nm which is
attributed to an e2g“e1g transition of the ferrocenyl
moiety [7]. As for (dppf)Pt(dmit) complex, however, a
medium intensity band observed at 466 nm (an n“p*
transition of CꢀS moiety) is overlapped with the weak
band from the ferrocenyl moiety.
(dppf)Pt(phdt): yield 84%; m.p. 185ꢀ187°C (dec.);
HR-FABMS Calc. for C44H36P2PtFeS4 1006.0181.
Found 1006.0173 (M+); FT-IR (KBr, cm−1) 3052 (Ar,
C–H), 2907 (–CH2), 1638, 1480, 1435 (Ar, CꢀC), 1385,
1306, 1167, 1096, 1026, 999, 858, 820, 745, 694 (Ar,
C–H), 639, 588, 556, 515, 494, 471, 442 (ring-tilt and
Fe–Cp in Fc); UV (CH3CN, nm) 220(st), 246(sh),
316(w), 444(w).
(dppf)Pt(dphdt): yield 93%; m.p. 173ꢀ174°C (dec.);
FABMS (m/z) 1081.77 (M+); FT-IR (KBr, cm−1
)
3055, 3034 (Ar, C–H), 1636, 1481, 1435 (Ar, CꢀC),
1387, 1304, 1265, 1167, 1098, 1028, 999, 889, 849, 818,
745, 694 (Ar, C–H), 637, 588, 554, 517, 492, 469, 442
(ring-tilt and Fe–Cp in Fc); UV (CH3CN, nm) 222(st),
248(sh), 304(w), 450(w).
(dppf)Pt(mtdt): yield 93%; m.p. 250ꢀ252°C (dec.);
HR-FABMS Calc. for C38H34P2PtFeS4 932.0023.
Found 932.0037 (M+); FT-IR (KBr, cm−1) 3052 (Ar,
C–H), 2976, 2913 (–CH3), 1638, 1480, 1435 (Ar, CꢀC),
1385, 1304, 1165, 1096, 1028, 999, 965, 870, 849, 826,
747, 696 (Ar, C–H), 637, 554, 517, 496, 471, 438
(ring-tilt and Fe–Cp in Fc); UV (CH3CN, nm) 214(st),
314(w), 438(w).
3.2. X-ray molecular structure
Molecular structures of (dppf)PtL (L=dmit, phdt
and i-mnt) with the selected atom numbering scheme

1942
D.-Y. Noh et al. / Polyhedron 20 (2001) 1939–1945
compared to the complexes which contain the less
strained five-membered rings such as (dppf)Pt(dmit)
,
,
(2.327(2) A), (dppe)Pt(dmit) (2.312(3) A) [9] and
,
(dppf)Pt(phdt) (2.311(1) A). And it also affects the
electrochemical properties of the complexes as will be
discussed below. Two types of (dppf)Pt(dmit) molecules
(denoted by A and B as shown in Fig. 1) are in a unit
cell, which are crystallographically independent. [Pt(d-
mit)] units are almost planar but the torsion angle of
P(1)–P(2)–S(2)–S(1) for molecule A (6.0°) is larger
than the corresponding angle for molecule B (2.9°). The
triclinic unit cell contains, together with six CHCl3
molecules, two A molecules and two B molecules which
form centrosymmetric pairs of A–A and B–B with a
head-to-tail mode. Crystal structures of (dppf)Pt(i-mnt)
and (dppf)Pt(phdt) show a similar pairing arrangement.
Molecular planarity of (dppf)Pt(phdt) is the worst out
of the three complexes: the ethylene moiety at the
periphery of phdt ligand is folded up with 55° of
folding angle and P2PtS2 core deviates from the planar-
ity with 10.0° of torsion angle for P(2)–S(2)–S(1)–P(1)
plane.
Fig. 1. ORTEP plot of (dppf)Pt(dmit)·1.5(CHCl3) structure (30% ellip-
soids). Solvent molecules are omitted for clarity.
3.3. 31P NMR and cyclic 6oltammetry
Fig. 2. ORTEP plot of (dppf)Pt(phdt) structure (30% ellipsoids).
The 31P NMR parameters for the platinum com-
plexes are collected in Table 5 along with the data
obtained by cyclic voltammetry measurements. The 31P
NMR spectra give a typical 1:4:1 triplet [16] centered at
12.760–14.631 ppm depending upon the dithiolate lig-
ands. The magnitude for the Pt–P coupling (JPt–P) falls
in the range of 2962–3237 Hz suggesting a cis coordi-
nation of the phosphine ligand [5]. The variation of the
NMR parameters can be attributed to the difference of
an electron-donation ability of the dithiolate ligand:
The better donor property of the dithiolate ligand like
phdt the complex contains, the weaker the electron
donation of P“Pt becomes. Therefore, 31P NMR reso-
nance peak at the higher field (14.518–14.631 ppm) and
the weaker Pt–P coupling (JPt–P=2989–3000 Hz) was
observed for (dppf)PtL complexes (L=dddt, phdt and
dphdt). On the other hand, the complex with a poor
electron-donor (or a good electron-acceptor) such as
i-mnt ligand, the P“Pt donation becomes promoted
due to the electron-withdrawing effect of i-mnt ligand
resulting in the low-field resonance (12.760 ppm) and a
strong Pt–P coupling (JPt–P=3237 Hz). This behaviour
can be observed more obviously in (dppf)PtCl2 complex
(l=11.152 ppm and JPt–P=3764 Hz).
Fig. 3. ORTEP plot of (dppf)Pt(i-mnt)·(CH2Cl2) structure (30% ellip-
soids). Solvent molecules are omitted for clarity.
are shown in Figs. 1–3. The crystal data and the
selected bond lengths and angles are collected in Tables
1–4. Dithiolate and dppf coordinate to Pt(II) as biden-
tate ligands, and that the P2PtS2 core has a distorted
square planar geometry with P(1)–Pt–P(2) bite angle
being larger than 96°. This bite angle is also larger than
that observed in (dppe)Pt(dmit) (85.2(1)°; dppe=1,2-
bis(diphenylphosphino)ethane) [9] due to the ferrocenyl
group in dppf ligand. As for the (dppf)Pt(i-mnt) com-
plex, in addition, the S(1)–Pt–S(2) angle is as small as
74.42(11)° due to the four-membered ring formation of
1,1-dithiolate ligand (i-mnt) with Pt(II). The strained
structure of Pt(i-mnt) moiety can cause the less effective
overlap between p(S) and d(Pt) orbitals and thereby the
The platinum complexes show different redox be-
haviour in CH2Cl2 depending upon the donor ability of
a dithiolate ligand. (Dppf)Pt(i-mnt) exhibits only one
reversible redox peak at E1/2=1.225 V, which is very
close to that of (dppf)PtCl2 (E1/2=1.275 V). It means
that the i-mnt ligand undergoes the strong electron-
withdrawing effect as the chloride ligand in (dppf)PtCl2
,
longer Pt–S distance (2.352(3) A). This fact is distinctly

D.-Y. Noh et al. / Polyhedron 20 (2001) 1939–1945
1943
Table 1
Crystal data and structure refinement for (dppf)Pt(dmit)·1.5(CHCl3), (dppf)Pt(phdt) and (dppf)Pt(i-mnt)·(CH2Cl2)
(dppf)Pt(dmit)·1.5(CHCl3)
(dppf)Pt(phdt)
(dppf)Pt(i-mnt)·(CH2Cl2)
Empirical formula
Formula weight
Crystal system
C77H59Cl9Fe2P4Pt2S10
2249.65
triclinic
C44H36FeP2PtS4
1005.85
monoclinic
C39H30Cl2FeN2P2PtS2
974.55
monoclinic
(
Space group
Unit cell dimensions
P1 (no. 2)
P21/n (no. 14)
P21/n (no. 14)
,
a (A)
15.3323(8)
17.3610(10)
19.1005(11)
69.3370(10)
69.0170(10)
66.3340(10)
4215.9(4)
2
1.772
4.296
2204
0.95×0.53×0.23
yellow
11.8051(2)
11.8712(2)
28.9891(4)
90.0
97.6270(10)
90.0
4026.61(11)
4
1.659
4.149
13.0408(2)
17.35960(10)
16.6756(2)
90.0
96.8030(10)
90.0
3748.49(8)
4
1.727
4.486
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
3
,
Z
Dcalc (Mg m−3
)
Absorption coeff. (mm−1
F(000)
)
1992
0.71×0.42×0.34
red brown
1912
0.21×0.22×0.71
red brown
Crystal size (mm3)
Colour
2q range for data collection (°)
Index ranges
1.18 to 24.69
−185h516, −205k520,
−225l513
19675/13680 [Rint=0.0735]
13680/0/937
1.139
R1=0.0502, wR2=0.1329
R1=0.0569, wR2=0.1442
1.510 and 1.938
1.42 to 24.71
−135h513, −135k59,
−335l534
18712/6812 [Rint=0.0408]
6812/0/469
1.70 to 24.85
−115h515, −205k55,
−115l519
6133/5265 [Rint=0.0623]
5265/0/442
Reflections collected/unique
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I)]
R indices (all data)
1.213
1.279
R1=0.0343, wR2=0.0683
R1=0.0392, wR2=0.0704
0.755 and 1.202
R1=0.0658, wR2=0.1424
R1=0.0712, wR2=0.1460
1.213 and 1.363
Largest difference peak and hole (e,
−3
,
A
)
does: (dppf)PtCl2 has been known to show more anodic
half-wave potential than that of uncoordinated dppf
due to the electron-withdrawing property of the chlo-
ride ligand as well as the Lewis-acid character of Pt(II)
ion [2,7]. The platinum complexes containing 1,2-dithi-
olate ligands such as mtdt, dmit, dddt, phdt, dphdt give
richer cyclic voltammograms than that of i-mnt com-
plex: mtdt complex shows three reversible redox peaks
and the others exhibit two reversible and one quasi-re-
versible peaks. The cyclic voltammograms of mtdt and
phdt complexes are demonstrated in Fig. 4. As to the
mtdt complex, for example, the electron density on the
ferrocene moiety is no more significantly withdrawn by
Pt(II) ion and diphenylphosphine moiety because the
mtdt ligand is a good electron-donor compared to the
i-mnt ligand. This can be further supported by the 31P
Table 2
,
Selected bond lengths (A) and bond angles (°) for
(dppf)Pt(dmit)·1.5(CHCl3)
Bond lengths
Pt–P(1)
Pt–S(1)
2.284(2)
2.3302(19)
1.748(8)
1.728(9)
1.715(9)
1.661(8)
2.281(2)
2.322(2)
1.732(8)
1.728(9)
1.718(9)
1.662(9)
Pt–P(2)
Pt–S(2)
2.3053(19)
2.323(2)
1.736(8)
1.752(8)
1.750(8)
1.333(11)
2.3131(19)
2.3306(19)
1.740(8)
1.745(9)
1.744(8)
1.350(11)
S(1)–C51)
S(3)–C(53)
S(4)–C(53)
S(5)–C(53)
Pt%–P(1%)
S(2)–C(52)
S(3)–C(51)
S(4)–C(52)
C(51)–C(52)
Pt%–P(2%)
Table 3
,
Selected bond lengths (A) and bond angles (°) for (dppf)Pt(phdt)
Pt%–S(1%)
Pt%–S(2%)
S(1%)–C(51%)
S(3%)–C(53%)
S(4%)–C(53%)
S(5%)–C(53%)
S(2%)–C(52%)
S(3%)–C51%)
S(4%)–C(52%)
C(51%)–C(52%)
Bond lengths
Pt–P(1)
Pt–S(1)
S(1)–C(51)
S(3)–C(51)
S(4)–C(52)
C(51)–C(52)
2.2921(13)
2.3119(14)
1.742(6)
1.756(6)
1.746(5)
1.336(8)
Pt–P(2)
Pt–S(2)
S(2)–C(52)
S(3)–C(54)
S(4)–C(53)
C(53)–C(54)
2.2767(13)
2.3097(13)
1.756(5)
1.770(8)
1.764(9)
Bond angles
P(1)–Pt–P(2)
P(2)–Pt–S(2)
P(2)–Pt–S(1)
P(1%)–Pt%–P(2%)
P(2%)–Pt%–S(1%)
P(2%)–Pt%–S(2%)
95.96(7)
86.54(7)
174.97(7)
96.37(7)
87.03(7)
176.33(7)
P(1)–Pt–S(2)
P(1)–Pt–S(1)
S(2)–Pt–S(1)
P(1%)–Pt%–S(1%)
P(1%)–Pt%–S(2%)
S(1%)–Pt%–S(2%)
173.85(7)
88.20(7)
89.59(7)
174.87(8)
87.30(7)
89.33(7)
1.331(11)
Bond angles
P(1)–Pt–P(2)
P(1)–Pt–S(2)
P(1)–Pt–S(1)
98.25(5)
169.84(5)
85.81(5)
P(2)–Pt–S(2)
P(2)–Pt–S(1)
S(2)–Pt–S(1)
88.80(4)
173.19(5)
87.90(5)

1944
D.-Y. Noh et al. / Polyhedron 20 (2001) 1939–1945
(E11/2=0.470 V) among those of the platinum com-
plexes measured in this study. It also suggests that
[dppf]+ formed during the first oxidation process is well
stabilized by [Pt(mtdt)] moiety. Consequently, the sec-
ond and the third half-wave potentials of mtdt complex
(E21/2=1.050 V and E13/2=1.405 V) correspond to the
Table 4
,
Selected bond lengths (A) and bond angles (°) for (dppf)Pt(i-
mnt)·(CH2Cl2)
Bond lengths
Pt–P(1)
Pt–S(2)
S(1)–C(51)
N(1)–C(53)
C(51)–C(52)
C(52)–C(54)
2.285(3)
2.338(3)
1.739(13)
1.137(19)
1.372(17)
1.43(2)
Pt–P(2)
Pt–S(1)
S(2)–C(51)
N(2)–C(54)
C(52)–C(53)
2.271(3)
2.365(3)
1.728(12)
1.121(18)
1.42(2)
redox processes of [Pt(mtdt)]o/+ and [Pt(mtdt)]+/2+
,
respectively. Compared to the redox behaviour of mtdt
complex, the platinum complex containing a cyclic
1,2-dithiolate ligand such as phdt, for example, gives
two reversible redox peaks at 0.625 and 1.295 V, and
one quasi-reversible peak at Epa=1.51 V. The E11/2 is
observed at a higher potential than that of mtdt com-
plex, indicating that phdt is not a better donor than
mtdt ligand. Judging from the JPt–P and E11/2 values, the
order of the donor ability of the dithiolate ligands can
be estimated as follows:
Bond angles
P(1)–Pt–P(2)
P(1)–Pt–S(2)
P(1)–Pt–S(1)
8.80(11)
168.22(11)
93.80(11)
P(2)–Pt–S(2)
P(2)–Pt–S(1)
S(2)–Pt–S(1)
2.96(11)
167.26(11)
74.42(11)
Table 5
31P NMR and cyclic voltammetry parameters for (dppf)PtL com-
plexes
mtdt\dddt:phdt:dphdt\dmit\i-mnt.
L
31P NMR a
Cyclic voltammetry b (V)
The dddt, phdt and dphdt ligands contain a 1,4-dithiin
ring in common which are known to be an extended
p-electron system [14]. The quasi-reversibility of the
third redox peak could be attributed to the properties
of these ligands as can be seen in the electrochemical
studies of [Pt(dddt)2]2− complex [17]. This can be ap-
plied to the dmit complex, too.
l (ppm)
JPt–P (Hz)
E11/2
E21/2
E31/2
2Cl
11.152
12.760
13.213
13.902
14.593
14.631
14.518
3764
3237
2962
3024
2989
3000
2989
1.275
1.225
0.470
0.915
0.660
0.625
0.615
i-mnt
mtdt
dmit
dddt
phdt
dphdt
1.050
1.325
1.340
1.295
1.245
1.405
1.69 c
1.56 c
1.51 c
1.47 c
a l (ppm)=−19.227 for dppf.
4. Supplementary material
b 0.01 M samples in CH2Cl2 at ca. 298 K, 0.1 M (n-Bu4N)·BF4
supporting electrolyte, 0.05 V s−1 scan rate, Pt-button working
electrode vs. Ag/Ag+, Pt wire counter electrode, E1/2=0.705 V for
ferrocene.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 145445–145447 for com-
pounds (dppf)Pt(dmit)·1.5(CHCl3), (dppf)Pt(phdt) and
(dppf)Pt(i-mnt)·(CH2Cl2), respectively. Copies of this
information may be obtained from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44-1233-336-033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
c Epa of the quasi-reversible processes.
Acknowledgements
This work was supported by Korea Research Foun-
dation Grant (KRF-99-D00272).
Fig. 4. Cyclic voltammograms of (dppf)Pt(mtdt) and (dppf)Pt(phdt)
measured in CH2Cl2 with Pt-button working electrode vs. Ag/Ag+
,
Pt wire counter electrode and 0.05 V s−1 scan rate.
References
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ing effect of i-mnt ligand [5]. Considering these facts
together, the first half-wave potential of mtdt complex
can be attributed to the redox process of Fc/Fc+ in
dppf and is observed at the most cathodic potential
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