(Fluoren-9-ylidene)methanedithiolato complexes of platinum: Synthesis, reactivity, and luminescence

Article abstract of DOI:10.1021/ic050748o

Platinum(II) complexes with (fluoren-9-ylidene)methanedithiolato and its 2,7-di-tert-butyl- and 2,7-dimethoxy-substituted analogues were obtained by reacting different chloroplatinum(II) precursors with the piperidinium dithioates (pipH)-[(2,7-R₂

Full text of DOI:10.1021/ic050748o

Inorg. Chem. 2005, 44, 7200−7213
(Fluoren-9-ylidene)methanedithiolato Complexes of Platinum: Synthesis,
Reactivity, and Luminescence1
|
Jose´ Vicente,†, Pablo Gonza´lez-Herrero,*,† Mar´ıa Pe´rez-Cadenas,† Peter G. Jones,‡, and
Delia Bautista§,#
Grupo de Qu´ımica Organometa´lica, Departamento de Qu´ımica Inorga´nica, Facultad de Qu´ımica,
UniVersidad de Murcia, Apdo. 4021, 30071 Murcia, Spain, Institut fu¨r Anorganische und
Analytische Chemie, Technische UniVersita¨t Braunschweig, Postfach 3329, 38023 Braunschweig,
Germany, and SACE, UniVersidad de Murcia, Apdo. 4021, 30071 Murcia, Spain
Received May 11, 2005
Platinum(II) complexes with (fluoren-9-ylidene)methanedithiolato and its 2,7-di-tert-butyl- and 2,7-dimethoxy-substituted
analogues were obtained by reacting different chloroplatinum(II) precursors with the piperidinium dithioates (pipH)-
[(2,7-R2C12H6)CHCS2] [R
Q2[Pt S2C C(C12H6R2-2,7)
prepared from PtCl2, piperidine, the corresponding QCl salt, and 1a
QCl, the complexes (pipH)22b and [Pt(pip)4]2b were isolated depending on the PtCl2:pip molar ratio. The neutral
complexes [Pt S2C C(C12H6R2-2,7)L2] [L PPh3, R H (3a), t-Bu (3b), OMe (3c); L PEt3, R H (4a), t-Bu
(4b), OMe (4c); L2 dbbpy, R H (5a), t-Bu (5b), OMe (5c) (dbbpy 4,4 -di-tert-butyl-2,2 -bipyridyl)] were
similarly prepared from the corresponding precursors [PtCl2L2] and 1a c in the presence of piperidine. Oxidation
of Q22b with [FeCp2]PF6 afforded the mixed Pt(II) Pt(IV) complex Q2[Pt2
Et4N+, Pr4N+). The protonation of (Pr4N)22b with 2 equiv of triflic acid gave the neutral dithioato complex [Pt2
CCH[C12H6(t-Bu)2-2,7]
Pr4N[Pt S2C C[C12H6(t-Bu)2-2,7]}{S2CCH[C12H6(t-Bu)2-2,7]
obtained by treating 7 with 2 equiv of 1,8-bis(dimethylamino)naphthalene (DMAN). The crystal structures of 3b and
5c CH2Cl2 have been solved by X-ray crystallography. All the platinum complexes are photoluminescent at 77 K
in CH2Cl2 or KBr matrix, except for Q26. Compounds 5a c and Q8 show room-temperature luminescence in fluid
)
}
H (1a), t-Bu (1b), or OMe (1c)] in the presence of piperidine. The anionic complexes
2] [R H, (Pr4N)22a; R t-Bu, (Pr4N)22b, (Et4N)22b; R OMe, (Pr4N)22c] were
c in molar ratio 1:2:2:2. In the absence of
{
d
)
)
)
−
{
d
)
)
)
)
)
)
)
′
′
−
−
{
S2Cd
C[C12H6(t-Bu)2-2,7]
}
4] (Q26, Q
)
{
S2-
}
4] (7). The same reaction in 1:1 molar ratio gave the mixed dithiolato/dithioato complex
{
d
}
] (Pr4N8) while the corresponding DMANH+ salt was
‚
−
solution. The electronic absorption and emission spectra of the dithiolato complexes reveal charge-transfer absorption
and emission energies which are significantly lower than those of analogous platinum complexes with previously
described 1,1-ethylenedithiolato ligands and in most cases compare well to those of 1,2-dithiolene complexes.
Introduction
properties, which make them interesting candidates for
numerous technological applications.2 The majority of in-
vestigations concentrate on 1,2-dithiolene complexes, i.e.,
those containing the parent ligands 1,2-ethylenedithiolate and
1,2-benzenedithiolate or their derivatives. The chemistry of
complexes with the 1,1-ethylenedithiolate structural isomers
has developed in parallel3 but has been studied to a lesser
extent, mostly because of the reduced degree of metal-ligand
Transition metal complexes with unsaturated dithiolato
ligands are currently the subject of intensive research because
of their outstanding electronic, spectral, magnetic, and redox
* To whom correspondence should be addressed. E-mail: pgh@um.es.
WWW: http://www.um.es/gqo/.
† Grupo de Qu´ımica Organometa´lica, Departamento de Qu´ımica Inor-
ga´nica, Facultad de Qu´ımica, Universidad de Murcia, Apdo. 4021, 30071
Murcia, Spain.
(1) (Fluoren-9-ylidene)methanedithiolato Complexes. 2. For part 1, see
ref 26.
(2) Karlin, K. D., Stiefel, E. I., Eds. Dithiolene Chemistry: Synthesis,
Properties, and Applications; Progress in Inorganic Chemistry Vol.
52; Wiley-Interscience: New York, 2004.
‡ Institut fu¨r Anorganische und Analytische Chemie, Technische Uni-
versita¨t Braunschweig, Postfach 3329, 38023 Braunschweig, Germany.
§ SACE, Universidad de Murcia, Apdo. 4021, 30071 Murcia, Spain.
| E-mail: jvs1@um.es. WWW: http://www.um.es/gqo/.
E-mail: p.jones@tu-bs.de.
(3) Coucouvanis, D. Prog. Inorg. Chem. 1970, 11, 233-371. Coucouvanis,
# E-mail: dbc@um.es.
D. Prog. Inorg. Chem. 1979, 26, 301.
7200 Inorganic Chemistry, Vol. 44, No. 20, 2005
10.1021/ic050748o CCC: $30.25
© 2005 American Chemical Society
Published on Web 08/30/2005

Platinum (Fluoren-9-ylidene)methanedithiolates
delocalization and subsequently diminished ability to undergo
facile redox changes. However, there has been considerable
interest in 1,1-ethylenedithiolates in connection with their
ability to form clusters4 and heteropolynuclear complexes,5
stabilize high oxidation states,6 or make use of multiple donor
atoms to form coordination polymers.7
been ascribed to a charge-transfer transition involving a
HOMO of mixed metal/dithiolato character and a LUMO
which is a diimine-based π* orbital. This transition has been
referred to as mixed-metal/ligand-to-ligand charge-transfer
(MMLLCT) or, more generally, charge-transfer-to-diimine.
The presence of strongly electron-withdrawing functional
groups is a common feature of the majority of 1,1-
ethylenedithiolato ligands described to date. In the case of
platinum, the most widely used ligands of this kind are i-mnt
(XYCdCS22- with X ) Y ) CN) and ecda (X ) CN, Y )
CO2Et),8-13,18,19 and all other ligands contain at least one CN,
C(O)R, or CO2R function,14,20-22 with the exception of
(cyclopentadienylidene)methanedithiolate, which was em-
ployed by Bereman for the preparation of anionic Ni, Pd,
and Pt complexes.23 Probably as a result of this, the
exhaustive studies based on systematic ligand variation,
which have been carried out to understand the influence of
dithiolato and diimine ligands in the photoluminescence of
their platinum complexes, have not found appreciable
differences among the 1,1-ethylenedithiolato complexes and
have attributed little or no influence to the substituents on
these ligands.15,16,18 Usually, the greatest differences are found
between 1,2-dithiolenes and 1,1-ethylenedithiolates, the
former showing much lower charge-transfer absorption and
emission energies.2
Following our work on the synthesis and study of the
reactivity and properties of gold, palladium, and platinum
complexes containing the 2,2-diacetyl-1,1-ethylenedithiolato
ligand,24,25 we recently started to investigate the reactivity
and emission properties of transition metal complexes
containing the (fluoren-9-ylidene)methanedithiolato ligand
and its 2,7-di-tert-butyl- and 2,7-bis(octyloxy)-substituted
derivatives with the preparation of the first series of gold
complexes.26 These ligands show remarkable differences with
respect to the previously used 1,1-ethylenedithiolates, which
are mainly due to the absence of strongly electron-withdraw-
ing substituents. Thus, the very low energies of the LMCT
emissions of the gold(I) complexes with (fluoren-9-ylidene)-
Platinum complexes with 1,1-ethylenedithiolates have been
the subject of intensive research because of their interesting
excited-state properties. Dianionic complexes of the type [Pt-
(1,1-ethylenedithiolato)2]2- 8 and neutral complexes [Pt(1,1-
ethylenedithiolato)L2] with phosphines, diphosphines, phos-
phates,9,10 and 1,5-cyclooctadiene11 are luminescent, and their
emissions have been assigned to a charge-transfer excited-
state involving a HOMO that is a mixture of dithiolate and
metal orbital character and a LUMO that is a dithiolate-based
π* orbital. Special attention has been devoted to platinum
diimine complexes containing 1,1-ethylenedithiolato or 1,2-
dithiolene ligands, which display solvatochromic behavior
and room-temperature luminescence in solution12-14 and have
been considered suitable candidates for applications as
photocatalysts in light-to-chemical energy conversion pro-
cesses.15-17 In these systems, the observed luminescence has
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Inorganic Chemistry, Vol. 44, No. 20, 2005 7201

Vicente et al.
Chart 1
Table 1. Crystallographic Data for 3b and 5c‚CH2Cl2
param
formula
3b
5c‚CH2Cl2
C58H54P2PtS2
1072.16
133(2)
C35H38Cl2N2O2PtS2
848.78
100(2)
fw
T (K)
λ (Å)
cryst syst
space group
a (Å)
b (Å)
c (Å)
0.710 73
orthorhombic
P212121
13.1260(8)
14.7812(8)
24.6345(14)
4779.5(5)
4
1.490
3.129
0.0193
0.0405
0.710 73
orthorhombic
P212121
8.1462(4)
17.0641(9)
24.0539(13)
3343.7(3)
4
1.686
4.516
0.0279
0.0670
V (Å3)
Z
methanedithiolate and its substituted derivatives, as well as
their facile oxidation to gold(III) under atmospheric condi-
tions, revealed a marked influence of the strongly electron-
donating character of the new ligands on the emission
properties and redox behavior of their complexes.
F
calcd (Mg m-3
)
µ (mm-1
R1a
)
wR2b
a R1 ) Σ||Fo| - |Fc||/Σ|Fo| for reflections with I > 2σ(I). b wR2 )
In this paper, we describe the preparation and character-
ization of the first series of platinum(II) complexes with
(fluoren-9-ylidene)methanedithiolate and its 2,7-di-tert-butyl-
and 2,7-dimethoxy-substituted derivatives (Chart 1) and
report on the effect of the electron-donating character of the
dithiolato ligands on their photoluminescence and reactivity.
The complexes studied are of the basic types [Pt(dithiolate)2]2-
and [Pt(dithiolate)L2], with L ) PPh3, PEt3 or L2 ) 4,4′-di-
tert-butyl-2,2′-bipyridyl (dbbpy). We also present the oxida-
tion and protonation reactions of the anionic complex with
(2,7-di-tert-butylfluoren-9-ylidene)methanedithiolate, which
lead to the formation of an unprecedented Pt(II)-Pt(IV)
dithiolato complex or dithioato complexes, respectively.
[Σ[w(Fo2 - Fc )2]/Σ[w(Fo )2]0.5 for all reflections; w-1 ) σ2(F2) + (aP)2 +
2
2
2
bP, where P ) (2Fc2 + Fo )/3 and a and b are constants set by the program.
visible absorption spectra were recorded on Unicam UV500 (range
190-900 nm) or Hitachi U-2000 (range 190-1100 nm) spectro-
photometers. Excitation and emission spectra were recorded on a
Jobin Yvon Fluorolog 3-22 spectrofluorometer with a 450 W xenon
lamp, double-grating monochromators, and a Hamamatsu R-928P
photomultiplier. The solid-state measurements were made in front-
face configuration using finely pulverized KBr dispersions of the
samples in 5 mm quartz NMR tubes; the solution measurements
were carried out in right angle configuration using degassed
solutions of the samples in 10 mm quartz fluorescence cells (298
K) or 5 mm quartz NMR tubes (77 K). The solvents used were
CH2Cl2 at 298 K and CH2Cl2, DMF/CH2Cl2/MeOH (1:1:1), or PrCN
at 77 K, as specified. For the low-temperature measurements a
liquid-nitrogen dewar with quartz windows was employed. Emission
quantum yields were calculated relative to [Ru(bpy)3](PF6)2 in
MeCN (Φ ) 0.062)28 at 298 K for those compounds which are
emissive at room temperature, using the method described by
Demas and Crosby.29
X-ray Structure Determinations. Crystals of 3b and 5c‚CH2-
Cl2 suitable for X-ray diffraction studies were obtained by slow
diffusion of Et2O into solutions of the compounds in CH2Cl2.
Numerical details are presented in Table 1. Data for 3b were
recorded on a Bruker SMART 1000 CCD diffractometer to 2θmax
60°; data for 5c‚CH2Cl2 on a Bruker SMART APEX diffractometer
to 2θmax 56°. Multiscan absorption corrections were performed
(program SADABS). The structures were refined on F2 using the
program SHELXL-97 (G. M. Sheldrick, University of Go¨ttingen).
Hydrogen atoms were included using rigid methyl groups or a riding
model. The Flack parameters refined to -0.014(2) and 0.039(6),
although the concept of absolute configuration is not applicable to
the bulk materials. Some restraints to local aromatic ring symmetry
or light atom displacement factor components were applied. One
methoxy group of 5c‚CH2Cl2 is disordered over two sites.
General Procedure for the Preparation of Q2[Pt{S2CdC-
(C12H6R2-2,7)}2] (Q22a-c). To a suspension of PtCl2 (1.30 mmol)
in CH2Cl2 (40 mL) were added piperidine (300 µL, 3.03 mmol)
and the corresponding QCl salt (2.66 mmol). A pale yellow solution
formed, which was filtered through Celite to remove a small amount
of colloidal Pt. Addition of dithioate 1a, 1b, or 1c (2.62 mmol) led
to immediate reaction with formation of an orange precipitate. After
the mixture was stirred for 1 h, the solvent was partially evaporated
Experimental Section
General Considerations, Materials, and Instrumentation. All
preparations were carried out at room temperature unless otherwise
stated. Solvents were dried by standard methods. The ligand
precursors piperidinium 9H-fluorene-9-carbodithioate and its 2,7-
di-tert-butyl- and 2,7-dimethoxy-substituted analogues (1a-c) were
prepared by following the published procedure.27 The platinum
compounds cis-[PtCl2L2] with L ) PPh3 or PEt3 were prepared
from commercial PtCl2 and the corresponding phosphine (1:2) in
CH2Cl2. The complex [PtCl2(dbbpy)] was prepared by refluxing
PtCl2 with dbbpy in Me2CO for 3 h and purified by recrystallization
from hot CHCl3. All other reagents were obtained from commercial
sources and used without further purification. NMR spectra were
recorded on Bruker Avance 200, 300, 400, or 600 spectrometers
usually at 298 K, unless otherwise indicated. Chemical shifts are
referred to internal TMS (1H and 13C{H}), external 85% H3PO4
(31P{H}), or external Na2PtCl6 195Pt{H}). The 13C{H} NMR
(
resonances arising from the cations are not given. The assignments
1
of the H and 13C{H} NMR spectra were made with the help of
HMBC and HSQC experiments. Chart 1 shows the atom numbering
of the dithiolato ligands. Solution conductivities were measured in
Me2CO or MeNO2 with a Crison microCM 2200 conductimeter.
Melting points were determined on a Reichert apparatus and are
uncorrected. Elemental analyses were carried out with a Carlo Erba
1106 microanalyzer. Infrared spectra were recorded in the range
4000-200 cm-1 on a Perkin-Elmer 16F PC FT-IR spectrophotom-
eter using Nujol mulls between polyethylene sheets or KBr pellets.
FAB mass spectra were recorded on a VG Autospec 5000 mass
spectrometer using 3-nitrobenzyl alcohol as matrix. ESI mass
spectra were recorded on an Agilent 1100 LC/MSD VL. UV-
(28) Caspar, J. V.; Meyer, T. J. J. Am. Chem. Soc. 1983, 105, 5583-5590.
(29) Demas, J. N.; Crosby, G. A. J. Am. Chem. Soc. 1970, 95, 7262-
7270.
(27) Vicente, J.; Gonza´lez-Herrero, P.; Garc´ıa-Sa´nchez, Y.; Pe´rez-Cadenas,
M. Tetrahedron Lett. 2004, 45, 8859-8861.
7202 Inorganic Chemistry, Vol. 44, No. 20, 2005

Platinum (Fluoren-9-ylidene)methanedithiolates
(15 mL) and the solid was filtered off, washed with CH2Cl2 (2 ×
5 mL) and MeOH (2 × 5 mL), and vacuum-dried to give Q22a-c.
Data for (Pr4N)22a. Yield: 41%. Anal. Calcd for C52.5H73ClN2-
PtS4: C, 59.57; H, 6.92; N, 2.67; S, 12.23. Found: C, 59.48; H,
7.09; N, 2.83; S, 12.04. Mp: 237 °C. ΛM (MeNO2, 1.2 × 10-4
M): 130 Ω-1 cm2 mol-1. IR (Nujol, cm-1): ν(CdCS2), 1500; ν-
procedure described for (pipH)22b but using equimolar amounts
of PtCl2 (372 mg, 1.40 mmol) and 1b (668 mg, 1.40 mmol) and 3
equiv of piperidine (420 µL, 4.25 mmol). Yield: 830 mg, 83%.
Anal. Calcd for C64H92N4Pt2S4: C, 53.54; H, 6.46; N, 3.90; S, 8.93.
Found: C, 53.62; H, 6.65; N, 3.97; S, 8.66. Mp: 207 °C (dec).
Λ
M (Me2CO, 4.2 × 10-4 M): 74 Ω-1 cm2 mol-1. IR (Nujol, cm-1):
1
(Pt-S), 341. 1H NMR [400.9 MHz, (CD3)2SO]: δ 8.65 (d, 3JHH
7.8 Hz, 4 H, H1, H8), 7.81 (d, 3JHH ) 7.6 Hz, 4 H, H4, H5), 7.18
)
ν(NH), 3280, 3165; ν(CdCS2), 1503; ν(Pt-S), 348. H NMR
[300 MHz, (CD3)2SO]: δ 8.79 (d, JHH ) 1.8 Hz, 2 H, H1, H8),
4
3
3
3
3
7.63 (d, JHH ) 8.1 Hz, 2 H, H4, H5), 7.22 (dd, JHH ) 8.1 Hz,
4JHH ) 1.8 Hz, 2 H, H3, H6), 2.88 (m, 8 H, NCH2), 1.55 (m, 12 H,
CH2), 1.36 (s, 18 H, t-Bu). 13C{1H} NMR [75.5 MHz, (CD3)2SO]:
δ 183.8 (CS2), 147.0 (C2, C7), 138.3 (C8a, C9a), 131.9 (C4a, C4b),
126.0 (C9), 119.5 (C1, C8), 118.7 (C3, C6), 117.4 (C4, C5), 44.7
(NCH2), 34.6 (CMe3), 31.8 (CMe3), 23.6 (CH2), 22.6 (CH2).
[Pt{S2CdC(C12H8)}(PPh3)2] (3a). To a solution of 1a (80 mg,
0.25 mmol) and piperidine (26 µL, 0.26 mmol) in CH2Cl2 (10 mL)
was added cis-[PtCl2(PPh3)2] (153 mg, 0.20 mmol), and the mixture
was stirred for 15 min. Partial evaporation of the clear orange
solution (2 mL) and addition of Et2O (15 mL) led to the precipitation
of a yellow microcrystalline solid, which was filtered off, washed
with MeOH (2 × 3 mL) and Et2O (2 × 3 mL), and vacuum-dried
to give 3a‚0.5Et2O. Yield: 120 mg, 60%. Anal. Calcd for
C52H43O0.5P2PtS2: C, 62.64; H, 4.35; S, 6.43. Found: C, 62.56; H,
4.63; S, 6.32. Mp: 130 °C (dec). IR (Nujol, cm-1): ν(CdCS2),
(t, JHH ) 7.6 Hz, 4 H, H2, H7), 7.04 (t, JHH ) 7.6 Hz, 4 H, H3,
3
H6), 3.10 (m, 16 H, NCH2), 1.58 (m, 16 H, CH2), 0.86 (t, JHH
)
7.3 Hz, 24 H, Me). 13C{1H} NMR [100.8 MHz, (CD3)2SO]: δ 187.1
(CS2), 137.8 (C8a, C9a), 134.0 (C4a, C4b), 125.3 (C9), 125.0 (C2,
C7), 122.5 (C1, C8), 121.1 (C3, C6), 118.3 (C4, C5).
Data for (Et4N)22b. Yield: 43%. Anal. Calcd for C60H88N2-
PtS4: C, 62.09; H, 7.64; N, 2.41; S, 11.05. Found: C, 61.73; H,
7.70; N, 2.51; S, 11.05. Mp: 242 °C. ΛM (MeNO2, 1.2 × 10-4
M): 128 Ω-1 cm2 mol-1. IR (Nujol, cm-1): ν(CdCS2), 1500; ν-
(Pt-S), 342. 1H NMR [400.9 MHz, (CD3)2SO]: δ 8.78 (d, 4JHH
)
1.6 Hz, 4 H, H1, H8), 7.63 (d, 3JHH ) 8.0 Hz, 4 H, H4, H5), 7.07
(dd, 3JHH ) 8.0 Hz, 4JHH ) 1.6 Hz, 4 H, H3, H6), 3.15 (q, 3JHH
)
7.2 Hz, NCH2, 16 H), 1.35 (s, 36 H, t-Bu), 1.11 (tt, 3JHH ) 7.2 Hz,
3JHN ) 1.7 Hz, 24 H, Me, Et4N+).
Data for (Pr4N)22b. Yield: 51%. Anal. Calcd for C68H104N2-
PtS4: C, 64.16; H, 8.24; N, 2.20; S, 10.08. Found: C, 64.42; H,
8.30; N, 2.38; S, 9.80. Mp: 230 °C. ΛM (MeNO2, 1.0 × 10-4 M):
134 Ω-1 cm2 mol-1. IR (Nujol, cm-1): ν(CdCS2), 1500; ν(Pt-
S), 338. 1H NMR [400.9 MHz, (CD3)2SO]: δ 8.78 (d, 4JHH ) 1.6
Hz, 4 H, H1, H8), 7.62 (d, 3JHH ) 8.0 Hz, 4 H, H4, H5), 7.07 (dd,
1
1530. H NMR (400.9 MHz, CDCl3): δ 8.26 (m, 2 H, H1, H8),
7.69 (m, 2 H, H4, H5), 7.52 (m, 12 H, o-H, Ph), 7.34 (m, 6 H,
p-H, Ph), 7.23 (m, 12 H, m-H, Ph), 7.09 (m, 4 H, H2, H3, H6,
3
H7), 3.47 (q, JHH ) 7.0 Hz, 2 H, CH2, Et2O), 1.21 (t, 3 H,
Me, Et2O). 13C{1H} NMR (75.5 MHz, CDCl3): δ 162.5 (CS2),
138.6 (C8a, C9a), 137.2 (C4a, C4b), 134.6 (m, o-C, Ph), 130.7
(m, p-C, Ph), 129.4 (m, i-C, Ph), 127.9 (m, m-C, Ph), 125.9 (C2,
C7), 124.4 (C1, C8), 123.6 (C3, C6), 118.4 (C4, C5) (C9 not
observed). 31P{H} NMR (121.5 MHz, CDCl3): δ 14.8 (1JPtP ) 3031
Hz).
4
3JHH ) 8.0 Hz, JHH ) 1.6 Hz, 4 H, H3, H6), 3.11 (m, NCH2, 16
3
H), 1.59 (m, CH2, 16 H), 1.34 (s, 36 H, t-Bu), 0.87 (t, JHH ) 7.2
Hz, 24 H, Me, Pr4N+).
Data for (Pr4N)22c. Yield: 60%. Anal. Calcd for C56H80N2O4-
PtS4: C, 57.56; H, 6.90; N, 2.40; S, 10.98. Found: C, 57.79; H,
6.54; N, 2.29; S, 11.00. Mp: 229 °C. ΛM (Me2CO, 2.3 × 10-4
M): 94 Ω-1 cm2 mol-1. IR (Nujol, cm-1): ν(CdCS2), 1500; ν-
[Pt{S2CdC[C12H6(t-Bu)2-2,7]}(PPh3)2] (3b). This yellow com-
plex was prepared as described for 3a, from cis-[PtCl2(PPh3)2] (143
mg, 0.19 mmol) and 1b (100 mg, 0.21 mmol). Yield: 151 mg,
76%. Anal. Calcd for C58H54P2PtS2: C, 64.97; H, 5.08; S, 5.98.
Found: C, 64.65; H, 5.25; S, 5.61. Mp: 120 °C (dec). IR (Nujol,
(Pt-S), 340. 1H NMR [300.1 MHz, (CD3)2SO]: δ 8.24 (d, 4JHH
)
2.2 Hz, 4 H, H1, H8), 7.55 (d, 3JHH ) 8.2 Hz, 4 H, H4, H5), 6.60
(dd, 4 H, H3, H6), 3.76 (s, 12 H, OMe), 3.10 (m, 16 H, NCH2),
3
1.58 (m, 16 H, CH2), 0.87 (t, JHH ) 7.2 Hz, 24 H, Me, Pr4N+).
13C{1H} NMR [75.5 MHz, (CD3)2SO]: δ 186.5 (CS2), 157.2 (C2,
C7), 139.1 (C8a, C9a), 128.0 (C4a, C4b), 125.4 (C9), 117.9 (C4,
C5), 108.6 (C3, C6), 106.9 (C1, C8), 54.9 (OMe).
cm-1): ν(CdCS2), 1538. H NMR (400.9 MHz, CDCl3): δ 8.33
1
(d, 4JHH ) 1.7 Hz, 2 H, H1, H8), 7.53 (d, 3JHH ) 8.0 Hz, 2 H, H4,
H5), 7.49 (m, 12 H, o-H, Ph), 7.32 (m, 6 H, p-H, Ph), 7.22 (m, 12
3
4
H, m-H, Ph), 7.10 (dd, JHH ) 8.0 Hz, JHH ) 1.7 Hz, 2 H, H3,
H6), 1.21 (s, 18 H, t-Bu). 13C{1H} NMR (100.8 MHz, CDCl3): δ
159.5 (CS2), 148.2 (C2, C7), 139.0 (C8a, C9a), 134.9 (C4a, C4b),
134.6 (m, o-C, Ph), 130.6 (m, p-C, Ph), 129.4 (m, i-C, Ph), 127.9
(m, m-C, Ph), 121.7 (C1, C8), 120.8 (C3, C6), 117.5 (C4, C5),
34.6 [C(CH3)3], 31.7 [C(CH3)3] (C9 not observed). 31P{H} NMR
(162.3 MHz, CDCl3): δ 19.6 (1JPtP ) 3018 Hz).
(pipH)2[Pt{S2CdC(C12H6R2-2,7)}2] ((pipH)22b). To a suspen-
sion of PtCl2 (272 mg, 1.02 mmol) in CH2Cl2 (50 mL) was added
piperidine (250 µL, 2.53 mmol), and the resulting pale yellow
solution was filtered through Celite to remove a small amount of
colloidal Pt. Addition of 1b (973 mg, 2.04 mmol) led to immediate
reaction with formation of an orange precipitate, which was filtered
off, washed with CH2Cl2 (2 × 5 mL), and vacuum-dried to give
(pipH)22b. Yield: 810 mg, 74%. Anal. Calcd for C54H72N2PtS4:
C, 60.47; H, 6.77; N, 2.61; S, 11.96. Found: C, 60.39; H, 6.89; N,
2.72; S, 11.63. Mp: 239 °C. ΛM (Me2CO, 4.7 × 10-4 M): 83 Ω-1
cm2 mol-1. IR (Nujol, cm-1): ν(NH), 3168; ν(CdCS2), 1506; ν-
[Pt{S2CdC[C12H6(OMe)2-2,7]}(PPh3)2] (3c). This yellow com-
plex was prepared as described for 3a, from cis-[PtCl2(PPh3)2] (159
mg, 0.21 mmol) and 1c (86 mg, 0.22 mmol). Yield: 83 mg, 40%.
Anal. Calcd for C52H42O2P2PtS2: C, 61.23; H, 4.15; S, 6.29.
Found: C, 61.40; H, 4.24; S, 6.07. Mp: 125 °C (dec). IR (Nujol,
(Pt-S), 348. 1H NMR [300.1 MHz, (CD3)2SO]: δ 8.78 (d, 4JHH
1.5 Hz, 4 H, H1, H8), 7.63 (d, 3JHH ) 7.8 Hz, 4 H, H4, H5), 7.07
)
1
cm-1): ν(CdCS2), 1537. H NMR (400.9 MHz, CDCl3): δ 7.86
3
4
(d, 4JHH ) 2.2 Hz, 2 H, H1, H8), 7.51 (m, 12 H, o-H, Ph), 7.44 (d,
3JHH ) 8.3 Hz, 2 H, H4, H5), 7.32 (m, 6 H, p-H, Ph), 7.23 (m, 12
H, m-H, Ph), 6.65 (dd, 2 H, H3, H6), 3.63 (s, 6 H, OMe). 13C{1H}
NMR (100.8 MHz, CDCl3): δ 162.3 (CS2), 157.7 (C2, C7), 139.6
(C8a, C9a), 134.6 (m, o-C, Ph), 130.8 (C4a, C4b), 130.6 (m, p-C,
Ph), 129.4 (m, i-C, Ph), 128.8 (C9), 127.9 (m, m-C, Ph), 118.2
(C4, C5), 111.5 (C3, C6), 108.3 (C1, C8), 55.2 (OMe). 31P{H}
NMR (162.3 MHz, CDCl3): δ 19.3 (1JPtP ) 3030 Hz).
(dd, JHH ) 8.1 Hz, JHH ) 1.6 Hz, 4 H, H3, H6), 3.36 (br, 4 H,
NH2), 2.99 (m, NCH2, 8 H), 1.60 (m, CH2, 8 H), 1.53 (m, CH2, 4
H), 1.35 (s, 36 H, t-Bu). 13C{1H} NMR [100.8 MHz, (CD3)2SO]:
δ 183.6 (CS2), 147.3 (C2, C7), 138.5 (C8a, C9a), 132.1 (C4a, C4b),
126.3 (C9), 119.7 (C1, C8), 118.9 (C3, C6), 117.6 (C4, C5), 34.8
(CMe3), 32.0 (CMe3).
[Pt(pip)4][Pt{S2CdC[C12H6(t-Bu)2-2,7]}2] ([Pt(pip)4]2b). This
orange microcrystalline compound was obtained by following the
Inorganic Chemistry, Vol. 44, No. 20, 2005 7203

Vicente et al.
[Pt{S2CdC(C12H8)}(PEt3)2] (4a). This yellow complex was
prepared as described for 3a, from cis-[PtCl2(PEt3)2] (126 mg, 0.25
mmol) and 1a (93 mg, 0.28 mmol). Yield: 109 mg, 65%. Anal.
Calcd for C26H38P2PtS2: C, 46.49; H, 5.70; S, 9.55. Found: C,
46.48; H, 5.84; S, 9.42. Mp: 228 °C. IR (Nujol, cm-1): ν(Cd
CS2), 1527. 1H NMR (400.9 MHz, CDCl3): δ 8.73 (d, 3JHH ) 7.7
(324 mg, 0.61 mmol) and 1b (296 mg, 0.62 mmol). Yield: 428
mg, 86%. Anal. Calcd for C40H48N2PtS2: C, 58.87; H, 5.93; N,
3.43; S, 7.86. Found: C, 58.85; H, 6.14; N, 3.41; S, 7.56. Mp:
180 °C (dec). IR (Nujol, cm-1): ν(CdCS2), 1538, 1520. 1H NMR
4
(400.9 MHz, CDCl3): δ 8.82 (d, JHH ) 1.4 Hz, 2 H, H1, H8),
3
4
8.50 (d, JHH ) 5.9 Hz, 2 H, H6, dbbpy), 8.04 (d, JHH ) 1.7 Hz,
3
3
Hz, 2 H, H1, H8), 7.75 (d, JHH ) 7.4 Hz, 2 H, H4, H5), 7.26 (t,
2 H, H3, dbbpy), 7.67 (d, JHH ) 7.9 Hz, 2 H, H4, H5), 7.48 (dd,
3
3JHH ) 7.7 Hz, 2 H, H2, H7), 7.17 (t, JHH ) 7.4 Hz, 2 H, H3,
2 H, H5, dbbpy), 7.25 (dd, 2 H, H3, H6), 1.47, 1.42 (both s, 18 H
each, t-Bu). 13C{1H} NMR (100.8 MHz, CDCl3): δ 162.8 (C4,
dbbpy), 159.1 (CS2), 155.0 (C2, dbbpy), 148.6 (C2, C7), 147.3 (C6,
dbbpy), 138.8 (C8a, C9a), 134.9 (C4a, C4b), 130.0 (C9), 124.7
(C5, dbbpy), 121.4 (C3, C6), 119.9 (C1, C8), 119.8 (C3, dbbpy),
117.9 (C4, C5), 35.9, 35.0 (CMe3), 31.9, 30.2 (CMe3).
H6), 1.83 (m, 12 H, CH2), 1.16 (m, 18 H, Me, PEt3). 13C{1H} NMR
(75.5 MHz, CDCl3): δ 165.2 (CS2), 138.7 (C8a, C9a), 137.2 (C4a,
C4b), 129.9 (C9), 126.0 (C2, C7), 124.7 (C1, C8), 123.7 (C3, C6),
118.5 (C4, C5), 15.9 (m, CH2), 8.1 (3JPtC ) 23 Hz, Me, PEt3). 31P-
{H} NMR (81.0 MHz, CDCl3): δ 4.0 (1JPtP ) 2902 Hz).
[Pt{S2CdC[C12H6(t-Bu)2-2,7]}(PEt3)2] (4b). This yellow com-
plex was prepared as described for 3a, from cis-[PtCl2(PEt3)2] (137
mg, 0.27 mmol) and 1b (132 mg, 0.28 mmol). Yield: 114 mg,
53%. Anal. Calcd for C34H54P2PtS2: C, 52.09; H, 6.94; S, 8.18.
Found: C, 51.72; H, 7.19; S, 8.02. Mp: 246 °C (dec). IR (Nujol,
[Pt{S2CdC[C12H6(OMe)2-2,7]}(dbbpy)] (5c). This purple com-
plex was prepared as described for 5a, from [PtCl2(dbbpy)] (359
mg, 0.93 mmol) and 1c (393 mg, 0.74 mmol). Yield: 444 mg,
79%. Anal. Calcd for C34H36N2O2PtS2: C, 53.46; H, 4.75; N, 3.67;
S, 8.40. Found: C, 53.31; H, 4.88; N, 3.78; S, 8.24. Mp: 190 °C
(dec). IR (Nujol, cm-1): ν(CdCS2), 1537. 1H NMR (400.9 MHz,
CDCl3): δ 8.61 (d, 3JHH ) 5.9 Hz, 2 H, H6, dbbpy), 8.33 (d, 4JHH
) 2.2 Hz, 2 H, H1, H8), 7.95 (d, 4JHH ) 1.8 Hz, 2 H, H3, dbbpy),
1
cm-1): ν(CdCS2), 1536. H NMR (400.9 MHz, CDCl3): δ 8.78
(d, 4JHH ) 1.7 Hz, 2 H, H1, H8), 7.60 (d, 3JHH ) 8.0 Hz, 2 H, H4,
3
4
H5), 7.19 (dd, JHH ) 8.0 Hz, JHH ) 1.7 Hz, 2 H, H3, H6), 1.90
(m, 12 H, CH2), 1.39 (s, 18 H, t-Bu), 1.20 (m, 18 H, Me, PEt3).
13C{1H} NMR (50.3 MHz, CDCl3): δ 162.7 (t, 3JPC ) 79 Hz, CS2),
148.4 (C2, C7), 139.1 (C8a, C9a), 134.9 (C4a, C4b), 130.4 (t, 4JPC
) 3 Hz, C9), 121.8 (C1, C8), 121.1 (C3, C6), 117.6 (C4, C5),
34.9 (CMe3), 31.8 (CMe3), 15.8 (m, CH2), 8.2 (3JPtC ) 22 Hz, Me,
PEt3). 31P{H} NMR (162.3 MHz, CDCl3): δ 3.28 (1JPtP ) 2894
Hz).
3
7.57 (d, JHH ) 8.1 Hz, 2 H, H4, H5), 7.48 (dd, 2 H, H5, dbbpy),
6.77 (dd, 2 H, H3, H6), 3.94 (s, 6 H, OMe), 1.42 (s, 18 H, t-Bu).
13C{1H} NMR (100.8 MHz, CDCl3): δ 163.0 (C4, dbbpy), 158.2
(C2, C7), 155.0 (C2, dbbpy), 147.7 (C6, dbbpy), 139.6 (C8a, C9a),
130.8 (C4a, C4b), 124.7 (C5, dbbpy), 119.5 (C3, dbbpy), 118.4
(C4, C5), 110.7 (C3, C6), 108.2 (C1, C8), 55.7 (OMe), 35.9 (CMe3),
30.2 (CMe3) (CS2, C9 not observed).
[Pt{S2CdC[C12H6(OMe)2-2,7]}(PEt3)2] (4c). This yellow com-
plex was prepared as described for 3a, from cis-[PtCl2(PEt3)2] (69
mg, 0.14 mmol) and 1c (71 mg, 0.18 mmol). Yield: 72 mg, 73%.
Anal. Calcd for C28H42O2P2PtS2: C, 45.96; H, 5.79; S, 8.76.
Found: C, 46.15; H, 5.99; S, 8.78. Mp: 240 °C (dec). IR (Nujol,
(Pr4N)2[Pt2{S2CdC[C12H6(t-Bu)2-2,7]}4] [(Pr4N)26]. To a sus-
pension of (Pr4N)22b (553 mg, 0.43 mmol) in THF (25 mL) was
added [FeCp2]PF6 (151 mg, 0.46 mmol), and the mixture was stirred
for 1.5 h. Partial evaporation of the resulting dark brown solution
(10 mL) and addition of Et2O (25 mL) caused the precipitation of
a reddish brown solid, which was filtered off, washed with MeOH
(2 × 5 mL), and vacuum-dried to give (Pr4N)26. Yield: 231 mg,
49%. Anal. Calcd for C112H152N2Pt2S8: C, 61.90; H, 7.05; N, 1.29;
S, 11.80. Found: C, 61.70; H, 7.27; N, 1.30; S, 11.70. Mp: 211
°C (dec). ΛM (Me2CO, 3.6 × 10-4 M): 121 Ω-1 cm2 mol-1. IR
1
cm-1): ν(CdCS2), 1532. H NMR (400.9 MHz, CDCl3): δ 8.31
(d, 4JHH ) 2.2 Hz, 2 H, H1, H8), 7.53 (d, 3JHH ) 8.2 Hz, 2 H, H4,
H5), 6.73 (dd, 2 H, H3, H6), 3.88 (s, 6 H, OMe), 1.90 (m, 12 H,
CH2), 1.19 (m, 18 H, Me, PEt3). 13C{1H} NMR (100.8 MHz,
CDCl3): δ 158.0 (C2, C7), 140.0 (C8a, C9a), 131.2 (C4a, C4b),
118.1 (C4, C5), 111.0 (C3, C6), 109.4 (C1, C8), 55.6 (OMe), 15.9
(m, CH2), 8.2 (3JPtC ) 22 Hz, Me, PEt3) (CS2 and C9 not observed).
31P{H} NMR (121.5 MHz, CDCl3): δ 4.19 (1JPtP ) 2903 Hz).
[Pt{S2CdC(C12H8)}(dbbpy)] (5a). To a solution of 1a (237 mg,
0.72 mmol) in CH2Cl2 (25 mL) were added piperidine (100 µL,
1.01 mmol) and [PtCl2(dbbpy)] (361 mg, 0.68 mmol). A dark purple
solution formed immediately, which was stirred for 10 min and
evaporated to dryness. Treatment of the residue with MeOH (12
mL) led to the formation of a purple precipitate, which was filtered
off, washed with MeOH (3 × 5 mL), and vacuum-dried to give
5a. Yield: 345 mg, 72%. Anal. Calcd for C32H32N2PtS2: C, 54.61;
H, 4.58; N, 3.98; S, 9.11. Found: C, 54.34; H, 4.73; N, 4.08; S,
1
(Nujol, cm-1): ν(CdCS2), 1510. H NMR [400.9 MHz, (CD3)2-
CO]: δ 8.90, 8.88, 8.52, 8.14 (all d, 4JHH ) 1.5 Hz, 2 H each, H1,
3
H8), 7.70, 7.67, 7.62, 7.47 (all d, JHH ) 8.0 Hz, 2 H each, H4,
3
4
H5), 7.30 (app td, JHH ) 8.0 Hz, JHH ) 1.5 Hz, 4 H, H3, H6),
7.16, 7.01 (both dd, 3JHH ) 8.0 Hz, 4JHH ) 1.5 Hz, 2 H each, H3,
H6), 3.11 (m, 16 H, NCH2), 1.52 (m, CH2, 16 H), 1.47, 1.40, 1.29,
3
1.13 (all s, 18 H each, t-Bu), 0.79 (t, JHH ) 7.2 Hz, 24 H, Me,
Pr4N+).
(Et4N)2[Pt2{S2CdC[C12H6(t-Bu)2-2,7]}4] [(Et4N)26]. This com-
pound was prepared as described for (Pr4N)26, from (Et4N)22b (93
mg, 0.08 mmol) and [FeCp2]PF6 (29 mg, 0.09 mmol). Yield: 73
mg, 89%. Anal. Calcd for C104H136N2Pt2S8: C, 60.61; H, 6.65; N,
1.36; S, 12.45. Found: C, 60.09; H, 6.46; N, 1.47; S, 12.19. Mp:
1
8.99. Mp: 200 °C (dec). IR (Nujol, cm-1): ν(CdCS2), 1522. H
4
NMR (400.9 MHz, CDCl3): δ 8.71 (d, JHH ) 7.7 Hz, 2 H, H1,
240 °C (dec). ΛM (Me2CO, 1.6 × 10-4 M): 149 Ω-1 cm2 mol-1
.
H8), 8.56 (d, 3JHH ) 5.9 Hz, 2 H, H6, dbbpy), 7.92 (d, 4JHH ) 1.8
IR (Nujol, cm-1): ν(CdCS2), 1514. 1H NMR [400.9 MHz, (CD3)2-
3
Hz, 2 H, H3, dbbpy), 7.80 (d, JHH ) 7.3 Hz, 2 H, H4, H5), 7.44
CO]: δ 8.94, 8.86, 8.55, 8.04 (all d, 4JHH ) 1.5 Hz, 2 H each, H1,
(dd, 2 H, H5, dbbpy), 7.32 (td, 4JHH ) 1.0 Hz, 3JHH ) 7.7 Hz, 2 H,
H8), 7.70, 7.66, 7.63, 7.49 (all d, JHH ) 8.0 Hz, 2 H each, H4,
3
4
3
H2, H7), 7.22 (td, JHH ) 1.0 Hz, JHH ) 7.6 Hz, 2 H, H3, H6),
1.39 (s, 18 H, t-Bu). 13C{1H} NMR (75.5 MHz, CDCl3): δ 163.0
(C4, dbbpy), 162.2 (CS2), 155.1 (C2, dbbpy), 147.6 (C6, dbbpy),
138.3 (C8a, C9a), 137.0 (C4a, C4b), 129.2 (C9), 126.0 (C2, C7),
124.6 (C5, dbbpy), 123.9 (C3, C6), 122.8 (C1, C8), 119.6 (C3,
dbbpy), 118.8 (C4, C5), 35.8 (CMe3), 30.2 (CMe3).
H5), 7.31, 7.29, 7.17, 7.03 (all dd, 3JHH ) 8.0 Hz, 4JHH ) 1.5 Hz,
3
2 H each, H3, H6), 3.24 (q, JHH ) 7.3 Hz, 16 H, NCH2), 1.45,
1.41, 1.31, (all s, 18 H each, t-Bu), 1.13 (tt, 3JHH ) 7.2 Hz, 3JNH
1.5 Hz, 24 H, Me, Et4N+), 1.12 (s, 18 H, t-Bu).
)
(PPN)2[Pt2{S2CdC[C12H6(t-Bu)2-2,7]}4] [(PPN)26]. To a sus-
pension of (Pr4N)26 (249 mg, 0.12 mmol) in CH2Cl2 (20 mL) were
added (PPN)Cl (330 mg, 0.57 mmol) and water (8 mL), and the
mixture was vigorously stirred for 15 min. The dark brown organic
[Pt{S2CdC[C12H6(t-Bu)2-2,7]}(dbbpy)] (5b). This dark blue
complex was prepared as described for 5a, from [PtCl2(dbbpy)]
7204 Inorganic Chemistry, Vol. 44, No. 20, 2005

Platinum (Fluoren-9-ylidene)methanedithiolates
layer was decanted, filtered through anhydrous MgSO4, and
concentrated (2 mL). Addition of MeOH (8 mL) led to the formation
of a dark brown solid, which was filtered off, washed with MeOH
(2 × 3 mL) and Et2O (2 × 3 mL), and vacuum-dried to give
(PPN)26. Yield: 298 mg, 86%. Anal. Calcd for C160H156N2Pt2S8:
C, 66.78; H, 5.46; N, 0.97; S, 8.91. Found: C, 66.59; H, 5.64; N,
1.05; S, 8.69. Mp: 200 °C (dec). ΛM (Me2CO, 4.4 × 10-4 M):
(10 mL) was added 1,8-bis(dimethylamino)naphthalene (22 mg,
0.10 mmol). A brownish red precipitate formed immediately, which
was filtered off, washed with Et2O (5 mL), and vacuum-dried to
give DMANH8. Yield: 104 mg, 92%. Anal. Calcd for C58H68N2-
PtS4: C, 62.39; H, 6.14; N, 2.51; S, 11.49. Found: C, 62.09; H,
6.14; N, 2.45; S, 11.32. Mp: 155 °C (dec). ΛM (Me2CO, 3.1 ×
10-4 M): 95 Ω-1 cm2 mol-1. IR (Nujol, cm-1): ν(CdCS2), 1514.
1H NMR [400.9 MHz, (CD3)2CO]: δ 8.80 (d, 4JHH ) 1.5 Hz, 2 H,
H1, H8, dithiolato), 8.09 (d, 3JHH ) 7.7 Hz, 4 H, H2, H4, H5, H7,
DMANH), 7.85 (br s, 2 H, H1, H8, dithioato), 7.73 (t, 3JHH ) 7.7
Hz, 2 H, H3, H6, DMANH), 7.70, 7.60 (both d, 3JHH ) 8.0 Hz, 2
144 Ω-1 cm2 mol-1. IR (Nujol, cm-1): ν(CdCS2), 1520. 1H NMR
4
[400.9 MHz, (CD3)2CO]: δ 8.94, 8.83, 8.56, 8.12 (all d, JHH
)
1.7 Hz, 2 H each, H1, H8), 7.73-7.49 (m, 66 H, PPN+ + H4,
H5), 7.41 (d, JHH ) 8.0 Hz, 2 H, H4, H5), 7.25-7.22 (m, 4 H,
3
3
4
3
H3, H6), 7.12, 6.94 (both dd, JHH ) 8.0 Hz, JHH ) 1.7 Hz, 2 H
each, H3, H6), 1.37, 1.33, 1.25, 1.07 (all s, 18 H each, t-Bu). 13C-
{1H} NMR [100.8 MHz, (CD3)2CO]: δ 174.9, 165.5, 152.5 (CS2),
149.4, 148.93, 148.88, 148.4 (C2, C7), 139.6, 139.5, 139.4 (C8a,
C9a, two signals clearly overlapped), 136.5, 135.6, 134.3, 134.0
(C4a, C4b), 128.7, 128.6 (C9, expected third signal probably
overlapped by PPN+ resonances), 123.3, 123.1 (C3, C6), 121.9,
121.6 (C1, C8), 121.4, 120.5 (C3, C6), 120.3, 119.5 (C1, C8) 118.7,
118.6, 118.0 (C4, C5, two signals clearly overlapped), 35.7, 35.5,
35.3 (CMe3, two signals clearly overlapped), 32.6, 32.5, 32.21,
32.18 (CMe3).
H each, H4, H5, dithioato and dithiolato), 7.48 (dd, JHH ) 8.0
4
3
Hz, JHH ) 1.6 Hz, 2 H, H3, H6, dithioato), 7.12 (dd, JHH ) 8.0
4
Hz, JHH ) 1.6 Hz, 2 H, H3, H6, dithiolato), 4.87 (s, 1 H, H9,
dithioato), 3.31, 3.30 (both s, 6 H each, NMe2), 1.38, 1.34 (both s,
18 H each, t-Bu).
Results and Discussion
Synthesis and Properties of Platinum(II) Complexes
with (Fluoren-9-yliden)methanedithiolato and Substituted
Derivatives. The platinum(II) complexes with (fluoren-9-
ylidene)methanedithiolato ligand and its 2,7-di-tert-butyl- and
2,7-dimethoxy-substituted analogues were obtained by react-
ing different chloroplatinum(II) precursors with the dithioates
(pipH)[(2,7-R2C12H6)CHCS2] [R ) H (1a), t-Bu (1b), or
OMe (1c)] in the presence of piperidine. As in the case of
the gold(I) and gold(III) complexes, the formation the
platinum(II) complexes is straightforward, taking place by
the displacement of the chloro ligands by the dithioates and
the subsequent deprotonation of the C9 carbon atom of the
9-fluorenyl moiety by the base.
The anionic complexes Q2[Pt{S2CdC(C12H6R2-2,7)}2],
where Q+ ) Pr4N+ for R ) H [(Pr4N)22a], Q+ ) Et4N+ or
Pr4N+ for R ) t-Bu (Q22b), or Q+ ) Pr4N+ for R ) OMe
[(Pr4N)22c], were prepared in moderate yields (40-60%)
from the reaction of PtCl2 with piperidine, the corresponding
QCl salt, and the piperidinium dithioates 1a-c in molar ratio
1:2:2:2 in CH2Cl2 (Scheme 1). Addition of piperidine to CH2-
Cl2 suspensions of PtCl2 results in the formation of clear
solutions presumably containing a mixture of cis- and trans-
[PtCl2(pip)2].30 The dithioates 1a-c displace the chloro and
piperidine ligands and are then deprotonated by the free
piperidine. In the presence of QCl salts (Q ) Pr4N+, Et4N+),
the poorly soluble compounds Q22a-c precipitate as orange
solids and can be separated from the piperidinium chloride
by washing with CH2Cl2. Attempts to obtain more soluble
salts by using bulkier cations resulted in very low yields
(Bu4N+) or were unsuccessful (PPN+ and Ph4P+). In absence
of QCl, the piperidinium salt (pipH)22b was obtained in 74%
yield. In an attempt to prepare the neutral complex [Pt{S2Cd
C[C12H6(t-Bu)2-2,7]}(pip)2] from the reaction of PtCl2, 1b,
and piperidine in molar ratio 1:1:3, the Magnus-type31 salt
[Pt(pip)4]2b was obtained in 83% yield. The salts of 2a-c
are moderately stable compounds both in the solid state and
in dimethyl sulfoxide solution.
[Pt2{S2CCH[C12H6(t-Bu)2-2,7]}4] (7). To a suspension of
(Pr4N)22b (209 mg, 0.16 mmol) in CH2Cl2 (20 mL) was added
trifluoromethanesulfonic acid (32 µL, 0.37 mmol). The resulting
dark red solution was stirred for 5 min and evaporated to dryness.
Treatment of the residue with pentane (20 mL) gave a precipitate
of Pr4N(CF3SO3) and a dark red solution. The solid was removed
by filtration and the clear filtrate evaporated to dryness to give 7
as a dark brown microcrystalline solid. Yield: 116 mg, 78%. Anal.
Calcd for C88H100Pt2S8: C, 58.58; H, 5.59; S, 14.22. Found: C,
58.60; H, 5.93; S, 14.13. Mp: 246 °C. IR (Nujol, cm-1): ν(CS2),
1
1025, 998. H NMR (600 MHz, CDCl3): δ 7.57, 7.45 (both d,
3JHH ) 8.0 Hz, 4 H each, H4, H5), 7.41, 7.40 (both br, 4 H each,
3
4
H1, H8), 7.36, 7.33 (both dd, JHH ) 8.0 Hz, JHH ) 1.6 Hz, 4 H
each, H3, H6), 5.44, 4.32 (both s, 1 H each, H9), 1.24, 1.22 (both
s, 36 H each, t-Bu). 13C{1H} NMR (150.9 MHz, CDCl3): δ 261.5,
239.8 (CS2), 150.6, 150.5 (C2, C7), 144.8, 139.9 (C8a, C9a), 138.7,
138.1 (C4a, C4b), 125.7, 125.0 (C3, C6), 122.9, 121.7 (C1, C8),
119.2 (C4, C5), 71.5, 68.2 (C9), 35.0, 34.9 (CMe3), 31.7, 31.6
(CMe3). 195Pt{1H} NMR (86.2 MHz, CDCl3): δ -3176.
Pr4N[Pt{S2CCH[C12H6(t-Bu)2-2,7]}{S2CdC[C12H6(t-Bu)2-
2,7]}] (Pr4N8). To a suspension of (Pr4N)22b (112 mg, 0.09 mmol)
in CH2Cl2 (15 mL) was added trifluoromethanesulfonic acid (8 µL,
0.09 mmol). Reaction took place immediately to give a violet
solution. Partial evaporation of the solvent (4 mL) and addition of
Et2O (5 mL) led to the formation of a violet precipitate, which
was filtered off, washed with a 2:3 (v/v) mixture of CH2Cl2 and
Et2O (2 × 3 mL), and vacuum-dried to give Pr4N8. Yield: 81 mg,
85%. Anal. Calcd for C56H77NPtS4: C, 61.85; H, 7.14; N, 1.29; S,
11.79. Found: C, 61.88; H, 7.22; N, 1.50; S, 11.83. Mp: 150 °C
(dec). ΛM (Me2CO, 3.0 × 10-4 M): 97 Ω-1 cm2 mol-1. IR (Nujol,
cm-1): ν(CdCS2), 1514; ν(Pt-S), 353, 364. 1H NMR (400.9 MHz,
4
CDCl3): δ 8.72 (d, JHH ) 1.6 Hz, 2 H, H1, H8, dithiolato), 7.81
(br s, 2 H, H1, H8, dithioato), 7.60 (app t, 3JHH ) 7.9 Hz, 4 H, H4,
3
4
H5, dithioato + dithiolato), 7.42 (dd, JHH ) 7.9 Hz, JHH ) 1.6
3
4
Hz, 2 H, H3, H6, dithioato), 7.14 (dd, JHH ) 7.9 Hz, JHH ) 1.6
Hz, 2 H, H3, H6, dithiolato), 4.85 (s, 1 H, H9, dithioato), 2.97 (m,
8 H, NCH2), 1.37 (s, 18 H, t-Bu), 1.35 (s, 18 H, t-Bu), 1.40-1.32
(m, 8H, CH2, overlapped by t-Bu signals), 0.70 (t, 3JHH ) 7.3 Hz,
12 H, Me, Pr4N+).
(30) Belluco, U.; Cattalini, L.; Turco, A. J. Am. Chem. Soc. 1964, 86, 3257-
3261. Kauffman, G. B.; Cowan, D. O. Inorg. Synth. 1965, 7, 249.
Cattalini, L.; Guidi, F.; Tobe, M. L. J. Chem. Soc., Dalton Trans.
1993, 233-236.
DMANH[Pt{S2CCH[C12H6(t-Bu)2-2,7]}{S2CdC[C12H6(t-Bu)2-
2,7]}] (DMANH8). To a solution of 7 (92 mg, 0.05 mmol) in Et2O
(31) Rodgers, M. L.; Martin, D. S. Polyhedron 1987, 6, 225-254.
Inorganic Chemistry, Vol. 44, No. 20, 2005 7205

Vicente et al.
Scheme 1
Scheme 2
character of the ligands, which had also been revealed by
the electronic absorption and emission properties of the gold-
(I) complexes. To investigate if the (fluoren-9-ylidene)-
methanedithiolato ligands would also facilitate the oxidation
of the platinum(II) complexes, we carried out the reactions
of Q22a-c with the mild oxidant [FeCp2]PF6. Although the
three complexes reacted at room temperature in THF, MeCN,
or Me2CO, only in the cases of the salts of 2b was one single
platinum product obtained, whose elemental analyses and
negative-ion FAB mass spectra were consistent with the
formulation Q2[Pt2{S2CdC[C12H6(t-Bu)2-2,7]}4] (Q26, Q )
Et4N+, Pr4N+) (Scheme 2). These salts are brownish red
microcrystalline solids that scarcely dissolve in CH2Cl2 or
CHCl3 and are only slightly more soluble in Me2CO and
dimethyl sulfoxide. To complete the characterization of the
dianion 6 by 13C{1H} NMR and to obtain single crystals
suitable for X-ray diffraction studies, we prepared the soluble
salt (PPN)26 (PPN+ ) [(Ph3P)2N]+) from (Pr4N)26 by cation
metathesis with (PPN)Cl in CH2Cl2/water. Preliminary
crystallographic studies on the Q26 salts (see below) revealed
that the dianion 6 is composed of one Pt(II) center in a
distorted square-planar environment and one Pt(IV) center
in a distorted octahedral environment, joined together by two
bridging dithiolato ligands, as depicted in Scheme 2. The
compounds Q26 (Q ) Et4N+, Pr4N+) can also be obtained
in moderate to high yields by reacting Q22b with anhydrous
FeCl3 or FeCl2 (1:1) in Me2CO, MeCN, or THF. The reaction
with FeCl2 succeeds only in the presence of atmospheric
oxygen and is not catalytic. The dianion 6 displays a very
high stability both in the solid state and in solution, and the
The neutral complexes [Pt{S2CdC(C12H6R2-2,7)L2], where
L ) PPh3 and R ) H (3a), t-Bu (3b), and OMe (3c), L )
PEt3 and R ) H (4a), t-Bu (4b), and OMe (4c), or L2 )
dbbpy for R ) H (5a), t-Bu (5b), and OMe (5c) (dbbpy )
4,4′-di-tert-butyl-2,2′-bipyridyl), were prepared in moderate
to high yields by displacement of the chloro ligands in the
corresponding precursors [PtCl2L2] with the dithioates 1a-c
in the presence of piperidine. In most cases, the piperidinium
chloride can be removed easily by washing the crude
products with MeOH or EtOH. The phosphine complexes
3a-c and 4a-c are remarkably stable yellow microcrystal-
line solids. In contrast, the diimine derivatives 5a-c are very
dark colored solids (purple or dark blue) and are sensitive
to visible light both in the solid state and in CHCl3 or CH2-
Cl2 solutions.32 Like the previously described complexes of
the type [Pt(dithiolato)(diimine)], compounds 5a-c display
a marked solvatochromism (see below).
Oxidation of Q22b. Formation of an Unprecedented Pt-
(II)-Pt(IV) Dithiolato Complex. We have recently reported
that the gold(I) complexes with (fluoren-9-ylidene)methane-
dithiolato ligand and its substituted analogues are readily
oxidized to gold(III) complexes under atmospheric conditions
or through their reactions with the organic acceptor TCNQ.26
This fact was attributed to the strong electron-donating
(32) Platinum diimine dithiolates which display low-energy charge-transfer-
to-diimine absorptions have been reported to undergo photooxidation
reactions. See, for example: Vogler, A.; Kunkely, H. J. Am. Chem.
Soc. 1981, 103, 1559-1560. Zhang, Y.; Ley, K. D.; Schanze, K. S.
Inorg. Chem. 1996, 35, 7102-7110. Connick, W. B.; Gray, H. B. J.
Am. Chem. Soc. 1997, 119, 11620-11627. We are currently investi-
gating the photoreactivity of 5a-c.
7206 Inorganic Chemistry, Vol. 44, No. 20, 2005

Platinum (Fluoren-9-ylidene)methanedithiolates
attempts to split it into Pt(II) and Pt(IV) complexes through
the reaction with excess NaCN or KSCN were unsuccessful.
As far as we are aware, the previously reported 1,1-
ethylenedithiolato complexes of Pt(IV) are limited to the
(cyclopentadienylidene)methanedithiolato derivative (Et4N)2-
[Pt(S2CdC5H4)3]23 and [PtBr2(tbcda)(dpphen)] (tbcda )
2-(tert-butoxycarbonyl)-2-cyano-1,1-ethylenedithiolate; dp-
phen ) 4,7-diphenyl-1,10-phenanthroline).33
Protonation of 2b. The protonation of the anionic
complexes 2a-c was attempted to explore the basic character
of the coordinated (fluoren-9-ylidene)methanedithiolato ligands
and the possibility of obtaining dithioato complexes. Only
in the case of complex 2b, containing the di-tert-butyl-
substituted dithiolato ligand, were compounds of definite
compositions obtained. The reaction of (Pr4N)22b with triflic
acid (HO3SCF3, HTfO) in molar ratio 1:2 in Et2O resulted
in the protonation of both dithiolato ligands at the C9 carbon
atom of the 2,7-di-tert-butylfluoren-9-ylidene moiety and the
formation of the dinuclear dithioato complex [Pt2{S2CCH-
[C12H6(t-Bu)2-2,7]}4] (7). This dark brown compound is
highly soluble in most organic solvents, including Et2O and
hexane, and can be easily separated from the (Pr4N)TfO and
isolated in almost quantitative yields. Although it was not
possible to grow crystals of 7 suitable for X-ray diffraction
studies, a dinuclear structure containing two bridging and
two chelating dithioato ligands (Scheme 2) can be proposed
Figure 1. Structure of complex 3b. Hydrogen atoms are omitted for clarity.
1
on the basis of its H and 13C NMR spectra, which reveal
the presence of two different dithioato ligands. This structure
has been found in a dinuclear (dithiocumato)platinum(II)
complex reported by Fackler and co-workers.34 The positive-
ion FAB mass spectrum of 7 shows the isotope distribution
corresponding to a dinuclear M+ ion. Compound 7 can also
be obtained directly by reacting PtCl2 with 1b (1:2) in CH2-
Cl2. The reaction of 7 with 2 equiv of piperidine resulted in
its deprotonation to give (pipH)22b.
When the protonation of (Pr4N)22b was carried out with
1 equiv of triflic acid, the mixed dithiolato/dithioato complex
Pr4N[Pt{S2CdC[C12H6(t-Bu)2-2,7]}{S2CCH[C12H6(t-Bu)2-
2,7]}] (Pr4N8) was obtained (Scheme 2), which can be
separated from the (Pr4N)TfO thanks to its lower solubility
in CH2Cl2/Et2O and isolated in high yield as a violet solid.
The anion 8 can also be obtained from the reaction of 7 with
1 equiv of the proton sponge (1,8-bis(dimethylamino)-
naphthalene ) DMAN) in Et2O, where the salt DMANH8
precipitates as a brownish red solid. Both Q8 salts are
unstable in solution under atmospheric conditions, undergo-
ing deprotonation and oxidation to form the Pt(II)-Pt(IV)
complex 6. The anion 8 is a rare example of mixed dithiolato/
dithioato complex.
Figure 2. Structure of complex 5c. Hydrogen atoms are omitted for clarity.
Table 2. Selected Bond Distances (Å) and Angles (deg) for 3b
Pt-P(1)
2.2958(6)
2.2980(6)
2.3222(6)
2.3259(6)
103.29(2)
165.426(19)
91.03(2)
S(1)-C(10)
S(2)-C(10)
C(9)-C(10)
1.756(2)
1.756(2)
1.362(3)
Pt-P(2)
Pt-S(1)
Pt-S(2)
P(1)-Pt-P(2)
P(1)-Pt-S(1)
P(2)-Pt-S(1)
P(1)-Pt-S(2)
P(2)-Pt-S(2)
S(1)-Pt-S(2)
74.33(2)
89.76(7)
89.64(7)
C(10)-S(1)-Pt
C(10)-S(2)-Pt
S(2)-C(10)-S(1)
91.51(2)
165.00(2)
106.16(10)
Table 3. Selected Bond Distances (Å) and Angles (deg) for 5c‚CH2Cl2
Pt(1)-N(2)
2.035(4)
2.048(4)
2.2745(13) C(9)-C(10)
2.2762(13)
78.86(16)
177.66(12)
103.24(11)
177.78(12)
102.73(12)
S(1)-C(10)
S(2)-C(10)
1.757(5)
1.757(5)
1.359(7)
Pt(1)-N(1)
Pt(1)-S(1)
Pt(1)-S(2)
N(2)-Pt(1)-N(1)
N(2)-Pt(1)-S(1)
N(1)-Pt(1)-S(1)
N(1)-Pt(1)-S(2)
N(2)-Pt(1)-S(2)
Crystal Structures of Complexes. The crystal structures
of 3b (Figure 1) and 5c‚CH2Cl2 (Figure 2) were determined
by X-ray diffraction studies. Selected bond distances
and angles are listed in Tables 2 and 3. Both structures
exhibit a square planar coordination around the plati-
S(1)-Pt(1)-S(2)
75.20(5)
90.23(16)
90.17(17)
104.4(3)
C(10)-S(1)-Pt(1)
C(10)-S(2)-Pt(1)
S(1)-C(10)-S(2)
num atom (mean deviations from plane: S2PtP2, 0.053 Å;
S2PtN2, 0.022 Å). The angles S-Pt-S of 74.33(2) (3b)
and 75.20(5)° (5c) are typical of four-membered CS2M
chelate rings, and the coordination geometries and Pt-S and
(33) Cummings, S. D.; Cheng, L. T.; Eisenberg, R. Chem. Mater. 1997, 9,
440-450.
(34) Fackler, J. P., Jr. J. Am. Chem. Soc. 1972, 94, 1009-1010. Burke, J.
M.; Fackler, J. P. Inorg. Chem. 1972, 11, 3000-3009.
Inorganic Chemistry, Vol. 44, No. 20, 2005 7207

Vicente et al.
1
Pt-N bond distances are very similar to those of the re-
lated complexes [Pt{S2CdC(COMe)2}(PPh3)2],25 [Pt(S2Cd
CHCOPh)(PPh3)2]20 and [Pt(S2CdCHCOFc)(PPh3)2] (Fc )
ferrocenyl),22 or [Pt{S2CdC(COMe)2}(dbbpy)] and [Pt-
{S2CdC(CN)(C6H4Br-4}(dbbpy)].14 The dithiolato ligands
are essentially planar [excluding substituents of the fluoren-
9-ylidene fragments; mean deviations from plane: 0.059 (3b)
and 0.029 Å (5c)].
equivalent atoms. As a result, the H NMR spectra show a
total of four singlets of the same intensity for the t-Bu groups
and four sets of signals for the aromatic protons (see
Experimental Section and Supporting Information). A 13C-
{1H} NMR spectrum could be measured only for the more
soluble PPN+ salt and shows four signals for each of the
carbon atoms of the dithiolato ligand, except for the CS2
and C9 atoms. The three expected resonances of the CS2
carbon atoms appear at δ 174.9, 165.5, and 152.5, the latter
displaying a higher intensity and being assignable to the
bridging ligands. Only two of the three expected C9
resonances are observable (at δ 128.7 and 128.6), probably
because one of them is overlapped by PPN+ resonances.
Crystals of the Et4N+, Pr4N+, and PPN+ salts of dianion
6, obtained from a variety of solvents, and also of the
DMANH+ salt, obtained from the aerial oxidation of
DMANH8 in Me2CO, were apparently suitable for crystal-
lographic studies, but they either underwent rapid loss of
solvent or, if stable enough to be handled, presented severe
twinning or disorder problems; therefore, the structures could
not be refined satisfactorily. However, in all cases the data
revealed unequivocally that complex 6 has the structure
depicted in Scheme 2, which can be viewed as a [Pt{S2Cd
C[C12H6(t-Bu)2-2,7]}3] unit, with a Pt(IV) in a distorted
octahedral environment, attached to a [Pt{S2CdC[C12H6(t-
Bu)2-2,7]}] fragment, containing the Pt(II) center, through
two sulfur atoms of different ligands. The Ph4P+ salt,
obtained as described for the PPN+ salt, crystallizes as a
dichloromethane disolvate in the space group P1h with a )
18.489(3), b ) 18.634(3), and c ) 19.573(3) Å and R )
99.389(4), â ) 94.922(4), and γ ) 108.726(3)° at -140
°C. The structure was refined to wR2 0.37, R1 0.13 (anion
Pt and S anisotropic, all other atoms isotropic, H atoms not
included; see the CIF file in Supporting Information) and
its qualitative nature established unambiguously, but large
features of residual electron density (9 e Å-3) precluded
satisfactory refinement. The crystal was probably twinned.
The presence of the dithioato ligands in complexes 7 and
Q8 is clearly confirmed by the resonances of the H9 atoms
of the 2,7-di-tert-butylfluoren-9-yl group, which appear in
the range δ 5.44-4.32. The H and 13C{1H} NMR spectra
of complex 7 show duplicate signals for each of the protons
and carbon atoms of the dithioato ligand, which is consistent
with the presence of two bridging and two chelating
dithioates as depicted in Scheme 2. The salts Q8 give rise
to almost identical resonances for the protons of the anion,
with one set of signals corresponding to a dithioato ligand
and another set corresponding to a symmetrical dithiolato
ligand.
1
IR Spectra. The solid-state infrared spectra of the platinum
complexes with the (fluoren-9-ylidene)methanedithiolato
ligand and its substituted derivatives show one or two bands
between 1500 and 1538 cm-1 assignable to the ν(CdCS2)
mode.35 As is the case with the previously described gold
complexes,26 the observed variations in the energies of the
ν(CdCS2) bands can be attributed to the oxidation state of
the metal center and the nature of the ligands attached to it,
which affect the strength of the π component of the CdCS2
bond. Usually, a higher oxidation state and/or the presence
of weaker donor ligands favor the resonance form A of the
(fluoren-9-ylidene)methanedithiolato ligand (Chart 1) and
increase the energy of the ν(CdCS2) band. Thus, the
dianionic complexes 2a-c give rise to the lowest energy
for this band (around 1500 cm-1), while the Pt(II)-Pt(IV)
complex 6 (1510-1520 cm-1), the monoprotonated 8 (1514
cm-1), and the neutral complexes 3a-c, 4a-c, and 5a-c
(1520-1538 cm-1) display appreciably higher energies. The
ν(Pt-S) band can be unequivocally assigned only for the
dianionic complexes 2a-c and appears around 340 cm-1.
Mass Spectra. The electrospray ionization (ESI) and/or
fast atom bombardment (FAB) mass spectra of complexes
(Pr4N)22b, (Pr4N)26, 7, Pr4N8, and DMANH8 were measured
to comfirm their nuclearity (see Supporting Information for
details). The most abundant peak in the negative ESI mass
spectrum of (Pr4N)22b appears at m/z 450 and corresponds
to the dianionic species 2b; the isotopic distributions cor-
responding to the monoanion resulting from the one-electron
oxidation of 2b and the ionic association Pr4N2b are also
observed (most intense peaks at m/z 900 and 1086, respec-
1
NMR Spectra. The H NMR spectra of the platinum
complexes with the (fluoren-9-ylidene)methanedithiolato
ligand and its substituted analogues show the signals cor-
responding to the aromatic protons of the ligands between
δ 8.94 and 6.60. The resonances of the H1 and H8 protons
(δ 8.94-7.86) are significantly downfield-shifted relative to
the free dithioates 1a-c and represent a distinctive charac-
teristic of coordinated (fluoren-9-ylidene)methanedithiolato
ligands.26 The 13C NMR spectra show the resonance of the
C9 atom within a very narrow range around δ 130, while
the chemical shift of the CS2 carbon atom undergoes
significant variations, being much higher for the anionic
derivatives Q22a-c (δ 187.1-183.2) than for the neutral 3a-
c, 4a-c, and 5a-c (δ 165.5-159.1). These variations agree
with the observations reported for the gold complexes,26 for
which the CS2 chemical shift decreases as the negative charge
on the complex decreases or as the oxidation state of the
metal center or its electron-accepting character increases.
1
The H NMR spectra of compounds Q26 (Q ) Et4N+,
Pr4N+, PPN+) and the 13C NMR spectrum of (PPN)26 are
fully consistent with the dinuclear structure depicted in
Scheme 2. The dianion 6 is a chiral molecule with overall
C2 symmetry in solution, containing three types of dithiolato
ligands. The two bridging dithiolates are equivalent to each
other but, in contrast to the chelating dithiolates, do not lie
along the C2 symmetry axis and therefore do not contain
(35) Jensen, K. A.; Henriksen, L. Acta Chem. Scand. 1968, 22, 1107-
1128.
7208 Inorganic Chemistry, Vol. 44, No. 20, 2005

Platinum (Fluoren-9-ylidene)methanedithiolates
Table 4. Electronic Absorption Data for Compounds 2-8 in CH2Cl2
Solution (ca. 5 × 10-5 M) at 298 K (λ > 330 nm)
tively). The isotope pattern of the ion pair Pr4N6 is observed
in both the negative-ion FAB and ESI mass spectra of
(Pr4N)26 at m/z 1985. The fragmentation of 6 gives funda-
mentally monoanionic 2b in FAB, while the softer ESI
technique allows the observation of several dinuclear species.
The positive-ion FAB mass spectrum of 7 shows the isotope
distribution corresponding to a dinuclear M+ ion at m/z 1804
with a relative abundance of 35%, while the most abundant
ion is the mononuclear species [Pt{S2CCH[C12H6(t-Bu)2-
2,7]}2]+, which most probably results from the fragmentation
of the M+ ion. In negative mode, the FAB MS of 7 displays
the isotopic distribution of monoanionic 2b as the most
abundant ion, while the partially deprotonated dinuclear
species [Pt2{S2CdC[C12H6(t-Bu)2-2,7]}2{S2CCH[C12H6(t-
Bu)2-2,7]}2]- and [Pt2{S2CdC[C12H6(t-Bu)2-2,7]}2{S2CCH-
[C12H6(t-Bu)2-2,7]}]- show up with very low relative
abundances at m/z 1802 and 1448, respectively, indicating
that they have a very low stability as compared to monoan-
ionic 2b. The ionization of 7 by the ESI technique was very
poor in CH2Cl2, and the compound is not soluble enough in
MeCN; therefore, consistent results were not obtained. The
most abundant isotope distribution observed in the ESI mass
spectra of Q8 (Q ) Pr4N+ and DMANH+), obtained from
freshly prepared MeCN or CH2Cl2 solutions in negative
mode, is attributable to the mononuclear anion 8. The pattern
is similar to that of monoanionic 2b but shifted by one unit
at higher m/z. However, its most intense peak occurs also at
m/z 900, and not the expected m/z 901, probably because of
the contribution of small amounts of monoanionic 2b. After
ca. 5 min in solution, the ESI mass spectra of Q8 show the
isotopic distribution of the dianion 2b at m/z 450, which
results from the deprotonation of 8.
compd
λ/nm (ꢀ/M-1 cm-1
)
(Pr4N)22a
(Pr4N)22b
[Pt(pip)4]2b
(Pr4N)22c
338 (12 500), 435 (sh, 7100), 501 (38 100)
337 (28 100), 428 (12 200), 490 (57 600)
408 (6100), 441 (14 100), 471 (30 000)
398 (20 500), 492 (46 100)
3a
398 (45 400)
3b
399 (47 800)
3c
396 (30 000)
4a
392 (26 600), 410 (26 900)
4b
391 (31 900), 408 (28 800)
4c
389 (35 500), 405 (30 900)
5a
5b
5c
383 (28 000), 399 (33 100), 532 (10 800)
381 (27 800), 397 (31 400), 543 (10 000)
388 (22 100), 395 (23 500), 531 (8200)
399 (sh), 417
399 (sh, 82 300), 420 (116 400)
347 (12 900), 388 (11 300), 509 (2800), 574 (1900)
383 (27 400), 401 (35 600), 534 (15 700)
384 (22 300), 402 (28 800), 535 (11 400)
(Pr4N)26a
(PPN)26
7
Pr4N8
DMANH8
a Accurate concentration and ꢀ values could no be meassured for this
compound due to its very low solubility.
for these low values. The molar conductivities of the Q8
salts [97 (Q ) Pr4N+) and 95 Ω-1 cm2 mol-1 (Q )
DMANH+)] are in good agreement with the reference values
given for 1:1 electrolytes.
Electronic Absorption Spectra. The UV-visible absorp-
tion spectra of the platinum compounds were measured in
the range 200-700 nm in CH2Cl2 at 298 K. All of them
display the bands arising from the fluoren-9-ylidene moiety
at around 230, 250, and 300 nm.26 The absorptions with λ
> 330 nm are listed in Table 4. The spectra of the dianionic
complexes Q22a-c show medium-intensity bands in the
330-340 and 400-430 nm regions and a very intense band
in the range 490-501 nm, the pattern being similar to that
observed for the isoelectronic gold(III) complexes [Au{S2Cd
C(C12H6R2-2,7)}2]- (R ) H, t-Bu, OC8H17).26 The spectra
of the phosphine complexes 3,4a-c also display very intense
bands above 330 nm; for the PPh3 complexes, only one band
of triangular shape is observed at around 400 nm, which
resolves into two bands for the PEt3 analogues at 390 and
410 nm. The intense lowest energy absorption band observed
for a number of dianionic bis(1,1-ethylenedithiolato)platinate-
(II)8,37 and neutral 1,1-ethylenedithiolatobis(phosphine)-
platinum(II)9,10 complexes has been assigned to a metal-to-
ligand charge-transfer (MLCT) transition for which the
HOMO is a mixture of metal and dithiolate orbital character
and the LUMO is a dithiolate-based π* orbital. The lowest
energy absorptions observed for Q22a-c, 3a-c, and 4a-c
can be given the same assignment on the basis of structural
similarity. Their large molar extinction coefficients are
comparable to those of analogous derivatives containing
i-mnt or ecda ligands8-10,37 and typical of charge-transfer
transitions in 1,1-ethylenedithiolato complexes.2 The lower
energies observed for the MLCT absorptions in the anionic
complexes Q22a-c relative to those in the neutral complexes
3,4a-c are consistent with the expected higher d orbital
energies in the anionic systems as compared to the neutral.
The variations due to the phosphine ligands in 3,4a-c are
Molar Conductivities. Because of their very low solubility
in Me2CO, the molar conductivities of (Pr4N)22a and Q22b
(Q ) Et4N+, Pr4N+) were measured in MeNO2 at concentra-
tions of ca. 1 × 10-4 M. The values found (128-134 Ω-1
cm2 mol-1) fall in the range given by Geary36 for 2:1
electrolytes in MeNO2 (115-250 Ω-1 cm2 mol-1); however,
accurate comparisons are not possible because the concentra-
tions employed for obtaining reference values (usually 10-3
M) were much higher. The conductivities of the rest of the
ionic compounds were measured in Me2CO at 5 × 10-4
M
or somewhat lower concentrations. The values found for
(pipH)22b and (Pr4N)22c (83 and 94 Ω-1 cm2 mol-1,
respectively) are considerably lower than expected for 2:1
electrolytes in Me2CO (range 160-200 Ω-1 cm2 mol-1),36
probably as a result of ion association. The conductivity of
[Pt(pip)4]2b (74 Ω-1 cm2 mol-1) is rather low relative to
reference values for 1:1 electrolytes (range 100-140 Ω-1
cm2 mol-1); although we have not found reference data for
bisdivalent electrolytes in the literature, this value confirms
the ionic nature of the compound. The salts Q26 (Q ) Et4N+,
Pr4N+, PPN+) gave conductivities in the range 121-149 Ω-1
cm2 mol-1, which are close to the lower limit of the reference
range given for 2:1 electrolytes; again, ion association and
probably the expected low mobility of dianion 6 may account
(36) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81-122.
(37) Werden, B. G.; Billig, E.; Gray, H. B. Inorg. Chem. 1966, 5, 78-81.
Inorganic Chemistry, Vol. 44, No. 20, 2005 7209

Vicente et al.
Table 5. Lowest Energy Absorption Band for Complexes 5a-c as a
Function of Solventa
λ
max, nm
solvent
toluene
THF
CHCl3
CH2Cl2
Me2CO
dimethyl sulfoxide
MeCN
5a
5b
5c
599
552
560
532
512
494
490
607
564
572
543
528
511
502
596
553
557
531
513
497
495
a 5 × 10-5 M.
small, but the lower MLCT energies observed for 4a-c
relative to 3a-c are attributable to the higher electron-
donating character of PEt3, which raises the energy of the
HOMO.10 When compared with analogous complexes con-
taining 1,1-ethylenedithiolates with electron-withdrawing
groups, the energies of the MLCT transitions in Q22a-c and
3,4a-c are considerably lower. Thus, in the cases of Q22a-
c, the MLCT band is up to 4250 cm-1 lower than that of the
anionic complexes [Pt(i-mnt)2]2- (413 nm)37 and [Pt(ecda)2]2-
(424 nm)8 and only comparable to those found for the closely
related (cyclopentadienyilidene)methanedithiolato derivative
(516 nm)23 and dithiolene complexes such as [Pt(mnt)2]2-
(474 nm)38 and [Pt(qdt)2]2- (510 nm).39 Likewise, the MLCT
energies observed for the phosphine complexes 3a-c and
4a-c are about 3840 or 3080 cm-1, respectively, lower than
those of [Pt(ecda)(PPh3)2] (346 nm) and [Pt(ecda)(PCy3)2]
(364 nm) but similar to that of [Pt(mnt)(PPh3)2] (410 nm).10
Although the nature of the dithiolato ligands is expected to
affect both the HOMO and LUMO energies, the considerably
reduced HOMO-LUMO gap in complexes Q22a-c, 3a-c,
and 4a-c with respect to the analogous derivatives with
i-mnt and ecda is most probably the result of an appreciably
higher HOMO energy, due to the strong electron-donating
character of the (fluoren-9-ylidene)methanedithiolato ligands.
The spectra of the diimine complexes 5a-c show three
absorption bands above 330 nm. In CH2Cl2 solution, the first
two bands are observed at 380 and 400 nm, with little
variations along the series, and have high molar extinction
coefficients (22 100-33 100 M-1 cm-1), while the third band
is very broad, stretching from 420 to 620 nm approximately,
and centered at 532 (5a), 543 (5b), or 531 (5c) nm, with
molar extinction coefficients of 10 800, 10 000, or 8200 M-1
cm-1, respectively. The higher energy bands are insensitive
to solvent variations and most probably arise from electronic
transitions within the dithiolato ligand.23 In contrast, the
broad, lowest energy absorption band is strongly solvent-
dependent and can be assigned to the Pt(d)/S(p)-π*diimine
solvatochromic transition typically observed for Pt(II) diimine
dithiolates.15 The UV-visible spectra of 5a-c in a variety
of organic solvents showed that this band shifts to lower
energy as solvent polarity decreases (Table 5; Figure 3). The
plots of the lowest absorption energies against the Pt(NN)-
(SS) solvent parameter introduced by Cummings and Eisen-
Figure 3. Absorption spectra of complex 5b in solvents of different
polarity (absorbance not to scale).
berg15 gave good linear correlations (R2 > 0.93; see
Supporting Information) and yielded solvatochromic shifts
of 0.21 (5a), 0.23 (5b), and 0.22 (5c) (in cm-1 × 10-3),
which are generally lower than those reported for the
solvatochromic transitions of other Pt(II) diimine dithiolates.
As is the case for the MLCT transitions observed for Q22a-
c, 3a-c, and 4a-c, the energies of the solvatochromic
transition in 5a-c in CH2Cl2 are much lower than in
analogous Pt(II) complexes containing dbbpy and 1,1-
ethylenedithiolates with electron-withdrawing functional
groups. For example, the solvatochromic absorptions of [Pt-
(tbcda)(dbbpy)] (437 nm), [Pt(cpdt)(dbbpy)] (434 nm)15 (cpdt
) 1-diethylphosphonate-1-cyanoethylene-2,2-dithiolate), and
[Pt{S2CdC(COMe)2}(dbbpy)] (452 nm)14 are about 3300
cm-1 higher in energy. Only analogous complexes with
dithiolenes such as 2,3-toluenedithiolate (tdt, 563 nm) and
maleonitriledithiolate (mnt, 497 nm) display a similar energy
for this transition. Since the energy of the diimine-based
LUMO is not expected to vary significantly with modifica-
tions of the dithiolato ligands,15 the reduced HOMO-LUMO
gap in complexes 5a-c with respect to their analogues tbcda,
cpdt, or 2,2-diacetyl-1,1-ethylenedithiolate must be attributed
to a considerably higher energy of the mixed metal/dithiolato
HOMO.
The salts Q26 (Q ) Pr4N+ and PPN+) have almost identical
absorption spectra. A very intense absorption is observed at
420 nm, which probably overlaps higher energy bands
(weakly pronounced shoulders are observed at 400 and 370
nm). The assignment of this band is uncertain, but its
intensity and energy suggest a MLCT transition, as observed
for the previously discussed complexes.
The absorptions of the dithioato complex 7 above 300 nm
occur as broad bands centered at 347, 388, 509, and 577 nm
and have molar extinction coefficients of ꢀ ) 12 900, 11 300,
2800, and 1900 M-1 cm-1, respectively. The first two bands
are most probably the result of the perturbation of the band
observed for the free dithioate 1b at 346 nm (ꢀ ) 12 000
M-1 cm-1), which arises from n-π* transitions within the
(38) Shupack, S. I.; Williams, R.; Gray, H. B.; Billig, E.; Clark, R. J. H.
J. Am. Chem. Soc. 1964, 86, 4594-4602.
(39) Cummings, S. D.; Eisenberg, R. Inorg. Chem. 1995, 34, 2007-2014.
CS2 group.26 The low intensity and energy of the 509 and
-
577 nm bands are typical of metal-centered d-d transitions.
7210 Inorganic Chemistry, Vol. 44, No. 20, 2005

Platinum (Fluoren-9-ylidene)methanedithiolates
Table 6. Excitation and Emission Data for (Pr4N)22a-c, 3a-c, and
4a-c in DMF/CH2Cl2/MeOH (1:1:1 v/v/v) Glasses at 77 Ka
Table 7. Excitation and Emission Data for 5a-c, 7, and Q8 in
Solutiona
b
compd
λexc
λem
298 Kb
λem Φem
77 Kc
d
(Pr4N)22a
(Pr4N)22b
(Pr4N)22c
3a
3b
3c
4a
4b
4c
454, 511
456, 510
458, 507
376, 395, 416
376, 394, 416
373, 416
372, 405, 416
372, 389, 410
372, 391, 414
587, 599, 642c
589, 602c
compd
5a
5b
5c
λexc
λexc
λem
380, 398, 537 700 2.0 377, 397, 450, 478, 516 595, 657e
380, 396, 548 711 1.7 377, 397, 457, 490, 524 608, 661e
376, 394, 535 698 2.3 371, 391, 456, 480, 516 626, 652e
584, 596,c 638c
562, 614, 676c
567, 618, 681c
561, 611, 672c
561, 610, 673c
561, 612, 674c
566, 618, 682c
7
400, 513, 569
714
703
704
Pr4N8
378, 398, 530 711 1.5 400, 432, 521
DMANH8 381, 400, 534 720 1.4 381, 404, 535
a In nm. The most intense peak is italicized. Emission spectra are
registered at the lowest energy excitation maximum. b In CH2Cl2. c In PrCN
a In nm. The most intense peak is italicized. b At the lowest energy
excitation maximum. c Shoulder.
glass (5a-c) or frozen CH2Cl2 solutions (7, Q8). ×104. e Shoulder.
d
The absorption spectra of Pr4N8 and DMANH8 are almost
identical in CH2Cl2 solution and show three bands at 380,
400, and 534 nm, which, surprisingly, are very similar in
energy, intensity, and shape to those of the diimine deriva-
tives 5a-c. The analogous gold(III) mixed dithiolato/
dithioato complexes [Au{S2CdC(C12H6R2-2,7)}{S2CCH-
(C12H6R2-2,7)}] (R ) H, t-Bu, OC8H17)26 give rise to similar
absorptions at slightly higher energies. The two higher energy
bands are therefore assignable to transitions within the
dithiolato ligand. The lowest energy broad band at 534 nm
is essentially not solvent-dependent, consistent with little or
no change in polarity between the ground and excited states.
Its origin is uncertain and can only be tentatively assigned.
Since a similar band is not observed in the spectra of the
bis(dithiolato) complexes Q22a-c or the dithioato derivative
7, it is clear that its existence requires the presence of both
dithiolato and dithioato ligands. Also, the higher energy
observed for this band in the analogous gold complexes
suggests a transition involving a HOMO of significant metal
orbital character. Given that the rest of the dithiolato
complexes described here share a common HOMO of mixed
metal/dithiolate orbital character, it is reasonable that the
transition responsible for this band involves a HOMO of
similar orbital nature. The LUMO is possibly a dithioate-
based π* orbital, which is expected to lie at a lower energy
than a similar dithiolate π* orbital,40 and thus the transition
could be described as a particular type of MMLLCT.
Figure 4. Excitation and emission spectra of (Pr4N)22a in CH2Cl2 (s)
and 3a in DMM glass at 77 K (‚‚‚) (normalized intensity).
Excitation and Emission Spectra. The compounds
(Pr4N)22a-c, 3a-c, 4a-c, 5a-c, 7, and Q8 (Q ) Pr4N+,
DMANH+) are photoluminescent at 77 K, and their excita-
tion and emission spectra have been measured both in the
solid state (KBr dispersions) and in DMM (DMF/CH2Cl2/
MeOH, 1:1:1), PrCN glasses, or frozen CH2Cl2 solutions.
Room-temperature luminescence in the solid state was
observed for all of them, whereas only the diimine complexes
5a-c and the mixed dithiolato/dithioato complex Q8 emit
in fluid CH2Cl2 solution at 298 K. The results of the
measurements in solution are summarized in Tables 6 and
7, and representative excitation and emission spectra are
shown in Figures 4-6. The solid-state excitation and
emission data at 298 and 77 K are given in the Supporting
Information. No detectable luminescence was observed for
the Q26 salts.
Figure 5. Excitation and emission spectra of 5c in CH2Cl2 at 298 K (s)
and PrCN glass at 77 K (‚‚‚) (normalized intensity). Emission spectra are
registered at the lowest energy excitation wavelength.
The emission spectra of the dianionic complexes (Pr4N)2-
2a-c in DMM glasses at 77 K display a sharp maximum in
the range 584-589 nm and less intense shoulders at 600
and 640 nm. When recorded in frozen CH2Cl2 solutions, the
spectra are almost identical with those obtained from DMM
glasses, but the shoulders resolve as sharp peaks for 2a,c
(Figure 4). These peaks could correspond to vibronic
progressions, since the spacings (332-375 and 1450-1508
cm-1) approximately coincide with the energies found for
the ν(Pt-S) and ν(CdCS2) modes in the solid state IR
spectra. The corresponding excitation spectra show the
absolute maximum at around 510 nm, which relates to the
MLCT band observed in the room-temperature absorption
(40) Piovesana, O.; Sestili, L. Inorg. Chem. 1979, 18, 2126-2129.
Inorganic Chemistry, Vol. 44, No. 20, 2005 7211

Vicente et al.
sponding excitation spectra closely reproduce the absorption
spectra, with two intense and narrow bands at 380 and 400
nm and a broad and less intense band at 537 (5a), 548 (5b),
or 535 (5c) nm, which coincides in energy with the charge-
transfer-to-diimine absorption. The room-temperature emis-
sion quantum yields are low ((1.7-2.3) × 10-4) but
comparable to those found for other Pt(II) dithiolates
containing dbbpy in CH2Cl2.15 The emission energies at 298
K did not vary significantly when the spectra were recorded
in PrCN. However, at 77 K in PrCN glass the emission band
sharpens and blue-shifts to around 600 nm and a shoulder
appears at 660 nm. Comparable blue-shifts on going from
fluid CH2Cl2 solutions to PrCN glasses have been found for
other Pt(II) diimine dithiolates and ascribed to a common
rigidochromic effect observed for many diimine com-
plexes.15,42 In all cases, the excitation spectra at 77 K were
identical when collected at the emission maximum or at the
shoulder wavelength. The two higher intensity peaks at 380
and 400 nm, which correspond to dithiolate-based absorp-
tions, are practically unaltered relative to the room-temper-
ature excitation spectra. However, the band corresponding
to the charge-transfer-to-diimine absorption, which is broad
at 298 K, shows some structure at 77 K, with three relative
maxima. It is also solvent dependent, undergoing the
expected blue-shift on going from CH2Cl2 to the more polar
PrCN solvent. Excitation at any of these maxima produced
the same emission spectra. The emissions of previously
described Pt(II) diimine complexes containing 1,1-ethylene-
dithiolates have been assigned as originating from multiple
emitting states, which include a triplet state with the same
orbital parentage as the charge-transfer-to-diimine absorption
and a diimine-based π-π* triplet state.13,18 The present
luminescence data for 5a-c at 77 K are consistent with an
assignment to charge-transfer-to-diimine excited states but
do not allow us to precisely establish a mixed origin for their
emissions. Also, the relatively large Stokes shifts observed
support a triplet multiplicity for the emitting states. The
emission energies of 5a-c are up to 2900 cm-1 (at 298 K
in CH2Cl2) or 3700 cm-1 (at 77 K in PrCN) lower than those
of the analogous tbcda, cpdt,15 and 2,2-diacetyl-1,1-ethyl-
enedithiolate14 derivatives but are similar to the emission
energy of the 3,4-toluenedithiolate complex.15
Figure 6. Excitation and emission spectra of Pr4N8 in CH2Cl2 at 298 K
(s) and 77 K (‚‚‚) (normalized intensity). Emission spectra are registered
at the lowest energy excitation wavelength.
spectra. The solid-state emission spectra display broad
maxima that are generally red-shifted with respect to the
solution emissions.41 The phosphine derivatives 3a-c and
4a-c give rise to very similar emission spectra in DMM
glasses at 77 K, with the absolute maximum at around 560
nm, a less intense peak at 610 nm, and a shoulder at 670
nm. The spacings between these peaks range from 1432 to
1518 cm-1 along the series, approaching in some cases the
energy of the ν(CdCS2) mode. The excitation spectra
collected at any of the emission peaks are identical and show
three maxima in the range 372-416 nm, which brackets the
wavelength range observed for the MLCT absorptions
(Figure 4). The solid-state emission spectra of 3a-c and
4a-c undergo only slight variations with respect to the
spectra in DMM glass. The luminescence of complexes of
the types bis(1,1-ethylenedithiolato)platinate(II)8 and 1,1-
ethylenedithiolatobis(phosphine)platinum(II)9,10 has been as-
signed as having the same orbital nature as the MLCT
absorptions but originating from a triplet excited state. The
above-mentioned excitation and emission data of Q22a-c,
3a-c, and 4a-c and the relatively large Stokes shifts
observed (∼2600 cm-1 for Q22a-c, ∼6500 cm-1 for 3a-c
and 4a-c) support the same assignment for these complexes.
The emission energies of the anionic complexes Q22a-c are
intermediate between those of the analogous complexes with
i-mnt (521 nm) and ecda (509 nm) and those of the dithiolene
complexes with mnt (712 nm) and qdt (643 nm).8 The
emissions of the phosphine derivatives in solution at 77 K
are also lower in energy than those of [Pt(ecda)(PPh3)2] (495
nm) and approach the energy observed for [Pt(mnt)(PPh3)2]
(597 nm).10 The emission energies of Q22a-c, 3a-c, and
4a-c are consistent with the low energies of the MLCT
absorptions, which have been discussed above.
The dithioato complex 7 emits at 714 nm in frozen CH2-
Cl2 solution at 77 K. The excitation spectrum closely
reproduces the absorption profile in the range 380-620 nm.
The emission and excitation spectra of this compound in
toluene glass at 77 K were identical with those obtained in
frozen CH2Cl2 solution. Luminescence data of related
dithioato complexes of platinum are not available for
comparison. The possible origins of this emission include
charge-transfer to dithioate and metal-centered transitions.
The Pr4N+ and DMANH+ salts of the mononuclear mixed
dithioato/dithiolato complex 8 are emissive in fluid CH2Cl2
solution at 298 K when excited at the lowest-energy
absorption wavelength (Figure 6). The emission band is broad
and maximized at 711 (Pr4N+) or 720 (DMANH+) nm. The
The diimine complexes 5a-c are emissive in fluid CH2-
Cl2 solution at 298 K, which is typical of platinum diimine
dithiolates;12-14 excitation at the charge-transfer-to-diimine
wavelength maximum results in broad emissions that are
maximized around 700 nm (Figure 5, Table 7). The corre-
(41) An emission band is observable at 542 or 544 nm in the solid-state
spectra of 2a,c at room temperature, probably arising from intraligand
transitions.
(42) Juris, A.; Balzani, V.; Barigelletti, F.; Campagna, S.; Belser, P.; von
Zelewsky, A. Coord. Chem. ReV. 1988, 84, 85-277.
7212 Inorganic Chemistry, Vol. 44, No. 20, 2005

Platinum (Fluoren-9-ylidene)methanedithiolates
corresponding excitation spectra are almost superimposable
on the absorption spectra at 298 K. For the measurements
at 77 K, the most suitable solvent was CH2Cl2 because the
salts Q8 underwent partial deprotonation in glass-forming
solvents or mixtures such as EtOH/MeOH, PrCN, and DMM
and were not soluble in toluene. The emission band in frozen
CH2Cl2 solutions is sharper and slightly blue-shifted, and
the excitation spectra are similar to those at room-temperature
in fluid CH2Cl2 solution. The transition responsible for the
emission of Q8 has probably the same orbital nature as the
lowest energy absorption, which we have tentatively assigned
to a MMLLCT. Further studies on the luminescence of
similar mixed dithiolato/dithioato platinum complexes are
underway to confirm this assignment.
significant influence on the absorption and emission energies
but are decisive for the stability of the oxidation and
protonation products of the anionic complexes 2a-c. Thus,
only in the case of the complex 2b, containing the di-tert-
butyl-substituted dithiolato ligand, did the oxidation and
protonation reactions give products of definite composition.
The oxidation of 2b with [FeCp2]PF6, FeCl3 or FeCl2/O2
resulted in the formation of a dinuclear mixed Pt(II)-Pt-
(IV) dithiolato complex (6) for which there is no precedent.
The behavior of 2b toward oxidation contrasts with that of
complexes of the type [Pt(1,2-dithiolene)2]2-, which usually
give stable, monomeric platinum(III) complexes.43 The
protonation of both dithiolato ligands in 2b resulted in the
formation of the neutral dinuclear dithioato complex 7, while
by protonating one of the ligands, the monomeric, anionic
mixed dithiolato/dithioato complex 8 was obtained. The
anion 8 is a new type of species which displays room-
temperature luminescence in fluid solution.
Conclusions
The first series of platinum complexes with (fluoren-9-
ylidene)methanedithiolate and its 2,7-di-tert-butyl- and 2,7-
dimethoxy-substituted analogues has been prepared from
chloroplatinum precursors and dithioates 1a-c. The elec-
tronic absorption and emission data of the anionic complexes
2a-c and the neutral phosphine complexes 3a-c and 4a-c
are consistent with previous assignments for related 1,1-
ethylenedithiolato complexes, which ascribe the lowest
energy absorptions and the emissions to charge-transfer
transitions involving a HOMO of mixed metal/dithiolate
orbital character and a dithiolate-based π* LUMO. The
diimine derivatives 5a-c display solvatochromic behavior
and room-temperature luminescence in fluid solution, which
can be ascribed to the charge-transfer-to-diimine transition
typically observed for platinum diimine dithiolates. Both the
absorption and emission energies of 2a-c, 3a-c, 4a-c, and
5a-c are generally much lower than those of analogous
complexes containing 1,1-ethylenedithiolates with electron-
withdrawing functional groups and, in most cases, compare
well with those of similar complexes with 1,2-dithiolene
ligands. These low energies can be generally attributed to
relatively high HOMO energies, which in turn are a
consequence of the strong electron-donating character of the
(fluoren-9-ylidene)methanedithiolato ligands. The R substit-
uents on the fluoren-9-ylidene moiety do not have a
Acknowledgment. We thank the Ministerio de Ciencia
y Tecnolog´ıa (Spain), FEDER (CTQ2004-05396), for finan-
cial support. P.G.-H. thanks Ministerio de Educacio´n y
Ciencia (Spain) and Universidad de Murcia for a contract
under the Ramo´n y Cajal Program. M.P.-C. thanks Ministerio
de Educacio´n y Ciencia (Spain) for a research grant. We
are grateful to J. M. Lo´pez-de-Luzuriaga and M. Monge
(Universidad de La Rioja, La Rioja, Spain) for their help
and advise regarding the measurements of excitation and
emission spectra.
Supporting Information Available: 1H NMR spectra of
1
(Pr4N)26, H and 13C{1H} NMR spectra of (PPN)26, mass spectra
of (Pr4N)22b, (Pr4N)26, 7, Pr4N8, and DMANH8, plots of the lowest
absorption energies of 5a-c vs the Pt(NN)(SS) solvent parameter,
solid-state excitation and emission data for (Pr4N)22b, 3a-c, 4a-
c, 5a-c, 7, Pr4N8, and DMANH8 (KBr dispersions), and crystal-
lographic data in CIF format for 3b, 5c‚CH2Cl2, and (Ph4P)26. This
material is available free of charge via the Internet at http://
pubs.acs.org.
IC050748O
(43) Robertson, N.; Cronin, L. Coord. Chem. ReV. 2002, 227, 93-127.
Clemenson, P. I. Coord. Chem. ReV. 1990, 106, 171-203.
Inorganic Chemistry, Vol. 44, No. 20, 2005 7213