Neutral and ionic complexes of C60 with metal dibenzyldithiocarbamates. Reversible dimerization of C60 ?- in ionic multicomponent complex [Crl(C 6H6)2?+]·(C 60?-)·0.5[Pd(dbdtc)2]

Article abstract of DOI:10.1021/ic051261i

New molecular complexes of C₆₀ with metal(II) dibenzyldithiocarbamates, M(dbdtc)₂·C₆₀·0. 5(C₆H₅Cl), where M = Cu^II, Ni^II, Pd^II, and Pt^II (1-4) and an ionic multicomponent complex [Cr^l(C₆H₆)₂^?+] ·(C₆₀^?-)·0.5[Pd(dbdtc)₂] (5) (Cr-(C₆H₆)S: bis(benzene)chromium) were obtained. According to IR, UV-visible-NIR, and EPR spectra, 1-4 involve neutral components, whereas 5 comprises neutral Pd(dbdtc)₂ and C ₆₀^?- and Cr^l(C₆H ₆)₂^?+ radical ions. The crystal structure of 5 at 90 K reveals strongly puckered fullerene layers alternating with those composed of Pd(dbdtc)₂. The Cr_l(C₆H ₆)₂^?+ radical cations are arranged between the layers. Fullerene radical anions form pairs within the layer with an interfullerene C...C contact of 3.092(2) A, indicating their monomeric state at 90 K. This contact is essentially shorter than the sum of van der Waals radii of two carbon atoms, and consequently, C₆₀ ^?- can dimerize. According to SQUID and EPR, single-bonded diamagnetic (C₆₀^-)₂ dimers form in 5 below 150-130 K on slow cooling and dissociate above 150-170 K on heating. The hysteresis was estimated to be 20 K. For the (C₆₀^-) ₂ dimers in 5, the dissociation temperature is the lowest among those for ionic complexes of C₆₀ (160-250 K). Fast cooling of the crystals within 10 min from room temperature down to 100 K shifts dimerization temperatures to lower than 60 K. This shift is responsible for the retention of a monomeric phase of 5 at 90 K in the X-ray diffraction experiment.

Full text of DOI:10.1021/ic051261i

Inorg. Chem. 2005, 44, 9547−9553
Neutral and Ionic Complexes of C60 with Metal
•-
Dibenzyldithiocarbamates. Reversible Dimerization of C60 in Ionic
•+
•-
Multicomponent Complex [CrI(C6H6)2 ]·(C60 )·0.5[Pd(dbdtc)2]
Dmitri V. Konarev,*,†,‡ Andrey Yu. Kovalevsky,§ Akihiro Otsuka,†,£ Gunzi Saito,*,† and
Rimma N. Lyubovskaya‡
DiVision of Chemistry, Graduate School of Science, Kyoto UniVersity, Sakyo-ku, Kyoto 606-8502,
Japan, Institute of Problems of Chemical Physics RAS, ChernogoloVka, Moscow region 142432,
Russia, Department of Chemistry, State UniVersity of New York at Buffalo, Buffalo, New York
14260, Research Center for Low Temperature and Materials Sciences, Kyoto UniVersity, Sakyo-ku,
Kyoto 606-8502, Japan
Received July 27, 2005
New molecular complexes of C60 with metal(II) dibenzyldithiocarbamates, M(dbdtc)2
‚
C60
‚
)
0.5(C6H5Cl), where M
)
•+
•-
CuII, NiII, PdII, and PtII (1
−
4) and an ionic multicomponent complex [CrI(C6H6)2
]
‚(C60
‚
0.5[Pd(dbdtc)2] (5) (Cr-
(C6H6)2: bis(benzene)chromium) were obtained. According to IR, UV
−
visible
−
NIR, and EPR spectra, 1
−
4 involve
neutral components, whereas 5 comprises neutral Pd(dbdtc)2 and C60 and CrI(C6H6)2 radical ions. The crystal
structure of 5 at 90 K reveals strongly puckered fullerene layers alternating with those composed of Pd(dbdtc)2.
•-
•+
•+
The CrI(C6H6)2 radical cations are arranged between the layers. Fullerene radical anions form pairs within the
layer with an interfullerene C‚‚‚C contact of 3.092(2) Å, indicating their monomeric state at 90 K. This contact is
•-
essentially shorter than the sum of van der Waals radii of two carbon atoms, and consequently, C60 can dimerize.
-
According to SQUID and EPR, single-bonded diamagnetic (C60
cooling and dissociate above 150
dimers in 5, the dissociation temperature is the lowest among those for ionic complexes of C60 (160
)
dimers form in 5 below 150
−
130 K on slow
2
-
−
170 K on heating. The hysteresis was estimated to be 20 K. For the (C60
)
2
−250 K). Fast
cooling of the crystals within 10 min from room temperature down to 100 K shifts dimerization temperatures to
lower than 60 K. This shift is responsible for the retention of a monomeric phase of 5 at 90 K in the X-ray diffraction
experiment.
Introduction
fulvalenes,3 amines,3c,4 metallocenes,1,5 porphyrins and
metalloporphyrins,6 porphyrazines,7 and other compounds.1,3c
Both ferromagnetism4a and a reversible formation of σ-bond-
ed structures5e-g are observed in ionic compounds. Neutral
complexes are promising photoactive compounds since they
form excited ionic states8a and manifest photoconductivity8b
Fullerenes form a wide variety of molecular and ionic
donor-acceptor complexes with organic and organometallic
donors1 such as aromatic hydrocarbons,2 substituted tetrathia-
* To whom correspondence should be addressed. E-mail: konarev@
icp.ac.ru (D.V.K); saito@kuchem.kyoto-u.ac.jp (G.S.).
† Division of Chemistry, Graduate School of Science, Kyoto University,
Japan. Fax: +81-75-753-40-35.
(3) (a) Izuoka, A.; Tachikawa, T.; Sugawara, T.; Suzuki, Y.; Konno, M.;
Saito, Y.; Shinohara, H. J. Chem. Soc., Chem. Commun. 1992, 1472.
(b) Saito, G.; Teramoto, T.; Otsuka, A.; Sugita, Y.; Ban, T.; Kusunoki,
M.; Sakaguchi, K. Synth. Met. 1994, 64, 359. (c) Konarev, D. V.;
Lyubovskaya, R. N.; Drichko, N. V.; Yudanova, E. I.; Shulga, Yu.
M.; Litvinov, A. L.; Semkin V. N.; Tarasov, B. P. J. Mater. Chem.
2000, 803.
‡ Institute of Problems of Chemical Physics RAS, Chernogolovka,
Moscow region 142432, Fax: +007-096-515-54-20.
§ Department of Chemistry, State University of New York at Buffalo.
£ Research Center for Low Temperature and Materials Sciences, Kyoto
University.
(1) (a) Balch, A. L.; Olmstead, M. M. Chem. ReV. 1998, 98, 2123. (b)
Konarev, D. V.; Lyubovskaya, R. N. Russ. Chem. ReV. 1999, 68, 19.
(c) Reed, C. A.; Bolskar, R. D. Chem. ReV. 2000, 100, 1075.
(2) (a) Pe´nicaud, A.; Carreo´n, O. Y.; Perrier, A.; Watkin, D. J.; Coulon,
C. J. Mater. Chem. 2002, 12, 913. (b) Litvinov, A. L.; Konarev, D.
V.; Kovalevsky, A. Yu.; Neretin, I. S.; Slovokhotov, Yu. L.; Coppens,
P.; Lyubovskaya, R. N. CrystEngCommun. 2002, 4, 618.
(4) (a) Allemand, P.-M.; Khemani, K. C.; Koch, A.; Wudl, F.; Holczer,
K.; Donovan, S.; Gru¨ner, G.; Thompson, J. D. Science 1991, 253,
301. (b) Konarev, D. V.; Kovalevsky, A. Yu.; Litvinov, A. L.; Drichko,
N. V.; Tarasov, B. P.; Coppens, P.; Lyubovskaya, R. N. J. Solid State
Chem. 2002, 168, 474. (c) Nadtochenko, V. A.; Moravskii, A. A.;
Gritsenko, V. V.; Shilov, G. V.; D’yachenko, O. A. Mol. Cryst. Liq.
Cryst. Sci, Technol., Sec. C 1996, 7, 103.
10.1021/ic051261i CCC: $30.25
Published on Web 11/05/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 25, 2005 9547

Konarev et al.
under photoexcitation. Recently, we have shown a butterfly-
shaped copper(II) diethyldithiocarbamate dimer,
[CuII(dedtc)2]2, to cocrystallize with C60 to produce
[CuII(dedtc)2]2‚C60 with a closely packed layered structure.
The excitation of the crystal of [CuII(dedtc)2]2‚C60 by white
light enhances photocurrent by a factor of 100.9 To extend
this work, we studied the cocrystallization of C60 with bulky
metal(II) dibenzyldithiocarbamates, M(dbdtc)2. Moreover,
ionic (D1•+)‚(fullerene•-)‚(D2) complex was obtained using
a multicomponent approach: D1 is a strong donor of small
size potentially able to ionize fullerene in solid state, and
D2 is a large neutral M(dbdtc)2 molecule defining a supramo-
lecular packing pattern. Bis(benzene)chromium (Cr(C6H6)2),
tetrakis(dimethylamino)ethylene (TDAE), decamethyl-
chromocene (Cp*2Cr), and decamethylcobaltocene (Cp*2Co)
were used as D1 components and cobalt(II) tetraphenylpor-
phyrinate (CoIITPP), cyclotriveratrylene (CTV), and N,N,N′,N′-
tetrabenzyl-p-phenylenediamine (TBPDA) were used as D2
components.10 We found unusual diamagnetic σ-bonded
Figure 1. Molecular components used for the preparation of 1-5 (M )
CuII, NiII, PdII, and PtII).
In this work, we present neutral complexes of C60 with
metal(II) dibenzyldithiocarbamates, M(dbdtc)2‚C60‚0.5(C6H5-
Cl), where M ) CuII, NiII, PdII, and PtII (1-4) and an ionic
multicomponentcomplex,[CrI(C6H6)2•+]‚(C60•-)‚0.5[Pd(dbdtc)2]
(5) (Figure 1). The crystal structure of 5 together with optical
(IR and UV-visible-NIR spectra) and magnetic properties
of 1-5 (EPR and SQUID) are discussed. It was shown that
•-
unusual dimerization of C60 is realized in 5 at the
temperature lowest among those known for ionic complexes
of C60. The peculiarities of this low-temperature dimerization
such as a hysteresis and a shift of dimerization temperature
depending on cooling rate were studied and compared with
•-
those for the C60 dimerization in other ionic complexes.
(CoIITPP‚fullerene-) anions in (D+)‚(CoIITPP‚C60-)‚solvent
-
(D is Cr(C6H6)210a and TDAE10b), and single-bonded (C60
)
2
Experimental Section
-
and (C70
)
dimers in (Cs+)2‚(C60(70)-)2‚CTV‚(DMF)x
2
Materials. Sodium dibenzyldithiocarbamate (Na(dbdtc)‚xH2O)
was purchased from Aldrich, bis(benzene)chromium Cr(C6H6)2 from
Strem Chemicals, and C60 of 99.98% purity from MTR Ltd. Sodium
dibenzyldithiocarbamate was recrystallized from an acetonitrile/
benzene mixture. M(dbdtc)2 (M ) Cu, Ni, Pd, Pt) was obtained by
stirring 2 equiv of Na(dbdtc) and 1 equiv of anhydrous CuBr2,
NiBr2, PdCl2, and PtCl2 salts (∼150 mg) (Aldrich) in 10 mL of
acetonitrile on heating (50 °C) for 4 h. After cooling, M(dbdtc)2
precipitated as brown (Cu), green (Ni), and light-yellow (Pd and
Pt) powders together with NaBr or NaCl. The powders were
dissolved in hot chlorobenzene, filtered off from NaBr or NaCl,
and the solvent was removed to dryness in a rotary evaporator to
afford pure M(dbdtc)2 compounds with satisfactory elemental
analyses (40-70% yield). Solvents were purified in argon atmo-
sphere. o-Dichlorobenzene (C6H4Cl2) and chlorobenzene (C6H5Cl)
were distilled over CaH2. Hexane and benzonitrile (C6H5CN) were
distilled over Na/benzophenone. For the synthesis of air-sensitive
5, solvents were degassed and stored in a glovebox. All manipula-
tions with 5 were carried out in a MBraun 150B-G glovebox with
controlled atmosphere and the content of H2O and O2 less than 1
ppm. The crystals were stored in a glovebox and were sealed in 2
mm quartz tubes for EPR and SQUID measurements under 10-5
Torr. KBr pellets for IR and UV-visible-NIR measurements of 5
were prepared in a glovebox.
Synthesis. The composition of 1-5 was determined from the
elemental analysis (Table 1) and was justified for 5 by X-ray
diffraction on a single crystal.
The crystals of 1 were obtained by the slow evaporation of
chlorobenzene/benzonitrile (12:1) solution (13 mL) containing C60
(25 mg, 0.0347 mmol) and an equimolar amount of Cu(dbdtc)2
(21 mg, 0.0347 mmol) during one week. The crystals precipitated
were decanted from the benzonitrile solution (∼1 mL) and were
washed with acetonitrile to afford black hexagonal plates with 70%
yield.
(DMF: N,N′-dimethylformamide; x ) 5-7).10c-d TBPDA
forms (D+)‚(C60•-)‚2(TBPDA) complexes (D: Cp*2Cr,
Cp*2Co, and TDAE), which exhibit a short-range antifer-
romagnetic interaction of spins.10b,e
(5) (a) Crane, J. D.; Hitchcock, P. B.; Kroto, H. W.; Teylor, R.; Walton,
D. R. M. J. Chem. Soc. Chem. Commun. 1992, 1767. (b) Wan, W.
C.; Liu, X.; Sweeney, G. M.; Broderick, W. E. J. Am. Chem. Soc.
1995, 117, 9580. (c) Konarev, D. V.; Khasanov, S. S.; Saito, G.;
Vorontsov, I. I.; Otsuka, A.; Lyubovskaya, R. N.; Antipin, Yu. M.
Inorg. Chem. 2003, 42, 3706. (d) Ho¨nnerscheid, A.; Wu¨llen, L.; Jansen,
M.; Rahmer, J.; Mehring, M. J. Chem. Phys. 2001, 115, 7161. (e)
Konarev, D. V.; Khasanov, S. S.; Saito, G.; Otsuka A.; Yoshida Y.;
Lyubovskaya R. N. J. Am. Chem. Soc. 2003, 125, 10074. (f)
Ho¨nnerscheid, A.; van Wu¨llen, L.; Dinnebier, R.; Jansen, M.; Rahmer,
J.; Mehring, M. Phys. Chem. Chem. Phys. 2004, 6, 2454. (g) Ketkov,
S. Yu.; Domrachev, G. A.; Ob’edkov, A. M.; Vasil’kov, A. Yu.;
Yur’eva, L. P.; Mehner, C. P. Russ. Chem. Bull. 2004, 53, 1932.
(6) (a) Olmstead, M. M.; Costa, D. A.; Maitra, K.; Noll, B. C.; Phillips,
S. L.; Van Calcar P. M.; Balch, A. L. J. Am. Chem. Soc. 1999, 121,
7090. (b) Boyd, P. D. W.; Hodgson, M. C.; Rickard, C. E. F.; Oliver,
A. G.; Chaker, L.; Brothers, P. J.; Bolskar, R. D.; Tham F. S.; Reed,
C. A. J. Am. Chem. Soc. 1999, 121, 10487. (c) Konarev, D. V.; Neretin,
I. S.; Slovokhotov, Yu. L.; Yudanova, E. I.; Drichko, N. V.; Shul’ga,
Yu. M.; Tarasov, B. P.; Gumanov, L. L.; Batsanov, A. S.; Howard J.
A. K.; Lyubovskaya, R. N. Chem. Eur. J. 2001, 7, 2605. (d) Ishii, T.;
Aizawa, N.; Kanehama, R.; Yamashita, M.; Sugiura, K.; Miyasaka,
H. Coord. Chem. ReV. 2002, 226, 113.
(7) Hochmuth, D. H.; Michel, S. L. J.; White, A. J. P.; Williams, D. J.;
Barrett A. G. M.; Hoffman, B. M. Eur. J. Inorg. Chem. 2000, 593.
(8) (a) Konarev, D. V.; Zerza, G.; Scharber, M. C.; Sariciftci, N. S.;
Lyubovskaya, R. N. Mol. Crys. Liq. Crys. 2005, 427, 3; 315. (b)
Lopatin, D. V.; Rodaev, V. V.; Umrikhin, A. V.; Konarev, D. V.;
Litvinov, A. L.; Lyubovskaya, R. N. J. Mater. Chem. 2005, 15, 657.
(9) Konarev, D. V.; Kovalevsky, A. Yu.; Lopatin, D. V.; Rodaev, V. V.;
Umrikhin, A. V.; Yudanova, E. I.; Coppens, P.; Lyubovskaya, R. N.;
Saito, G. Dalton Trans. 2005, 1821.
(10) (a) Konarev, D. V.; Khasanov, S. S.; Otsuka, A.; Yoshida, Y.;
Lyubovskaya, R. N.; Saito, G. Chem. Eur. J. 2003, 9, 3837. (b)
Konarev, D. V.; Neretin, I. S.; Saito, G.; Slovokhotov, Yu. L.; Otsuka,
A.; Lyubovskaya, R. N. Dalton Trans. 2003, 3886. (c) Konarev, D.
V.; Khasanov, S. S.; Vorontsov, I. I.; Saito, G.; Antipin, Yu. A.;
Otsuka, A.; Lyubovskaya, R. N. Chem. Commun. 2002, 2548. (d)
Konarev, D. V.; Khasanov, S. S.; Saito, G.; Lyubovskaya, R. N. Recent
Res. DeV. Chem. 2004, 2, 105. (e) Konarev, D. V.; Kovalevsky, A.
Yu.; Khasanov, S. S.; Saito, G.; Otsuka, A.; Coppens, P.; Lyubovskaya,
R. N. Eur. J. Inorg. Chem. 2005, in press.
Similar syntheses with Ni(dbdtc)2, Pd(dbdtc)2, and Pt(dbdtc)2 did
not afford crystals of the complexes with C60, and only the crystals
of the C60(C6H5Cl)x solvate were found according to the IR
spectrum. Because of this, we modified the synthetic procedure,
adding an excess of ferrocene to the starting solution. The crystals
9548 Inorganic Chemistry, Vol. 44, No. 25, 2005

Complexes of C60 with Metal Dibenzyldithiocarbamates
Table 1. Elemental Analysis Data for 1-5
elemental analysis, found/calcd
N
complex
C, %
H, %
N, %
Cl, %
1
Cu(dbdtc)2‚C60‚0.5(C6H5Cl)
79.61
80.58
81.94
81.07
79.31
78.21
75.32
73.63
80.86b
83.32
2.53
2.24
2.57
2.23
2.38
2.17
2.36
2.01
2.37
2.07
2.09
2.02
2.06
2.01
1.91
1.96
1.87
1.84
1.22
1.12
1.49
1.28
1.11
1.27
1.15
1.24
1.17
0.79
-
2
3
4
5
Ni(dbdtc)2‚C60‚0.5(C6H5Cl)
Pd(dbdtc)2‚C60‚0.5(C6H5Cl)
Pt(dbdtc)2‚C60‚0.5(C6H5Cl)
[Cr(C6H6)2]‚(C60)‚0.5[Pd(dbdtc)2]a
-
a The composition of the complex was consistent with the X-ray structure analysis on a single crystal. The unit cell parameters of several crystals from
the synthesis were tested to justify the identity of the crystals in one synthesis. b The lack of carbon content can be a result of partial oxygenation of
air-sensitive 5 while carrying out the elemental analysis.
of 2-4 were obtained by the slow evaporation of chlorobenzene/
benzonitrile (12:1) solution (13 mL) containing C60 (25 mg, 0.0347
mmol), an equimolar amount of M(dbdtc)2 (M ) Ni, Pd, Pt) (20-
25 mg, 0.0347 mmol), and Cp2Fe (50 mg, 0.268 mmol) during
one week. The crystals precipitated were decanted from the
benzonitrile solution (∼1 mL) and were washed with acetonitrile
to yield black hexagonal plates with 60-90% yield. According to
the IR spectra, the crystals precipitated were found to be ferrocene-
free and comprise only M(dbdtc)2 (M ) Ni, Pd, Pt), C60, and solvent
C6H5Cl molecules (Supporting Information).
The crystals of 5 were obtained by a slow diffusion of hexane
(25 mL) in 18 mL of the C6H4Cl2 solution containing C60 (25 mg,
0.035 mmol), Pd(dbdtc)2 (40 mg, 0.054 mmol), and Cr(C6H6)2 (12
mg, 0.057 mmol) in a glass tube 1.5 cm in diameter and 50 mL
volume with a ground glass plug. The starting solution was prepared
by dissolving all components by stirring at 60 °C for 4 h, and then
the resulting solution was cooled to room temperature, filtered, and
covered over with hexane. After 1 month, the crystals of 5 were
formed on the wall of the tube. The solvent was decanted from the
crystals precipitated, which were then washed with hexane to yield
black needles with 60% yield.
anode source (Mo KR radiation, λ ) 0.71073 Å) and equipped
with an Oxford Cryosystems nitrogen gas-flow apparatus. The data
were collected by the rotation method with 0.3° frame-width (ω
scan) and 10 s exposure time per frame. Four sets of data (600
frames in each set) were collected, nominally covering half of the
reciprocal space. The data were integrated, scaled, sorted, and
averaged using the SMART software package.22 In total, Ntot
)
17 488 reflections were measured up to 2θmax ) 50.14°; 8588 (Rint
) 0.050) of them were independent. The structures were solved
by the direct methods using SHELXTL NT Version 5.10.23 The
structure was refined by full-matrix least squares against F2. Non-
hydrogen atoms were refined in anisotropic approximation. Posi-
tions of hydrogen atoms were calculated geometrically. Subse-
quently, the positions of H-atoms were refined by the “riding”
model with Uiso) 1.2Ueq of the connected non-hydrogen atom. The
least-squares refinement on F2 was done to R1[I > 2σ(Ι)] ) 0.097
for 6656 observed reflections with F > 4σ(F), wR2 ) 0.279 (826
parameters), final GOF ) 1.110. The CCDC reference number is
275197.
Results and Discussion
General. UV-visible-NIR spectra were measured on a Shi-
madzu-3100 spectrometer in the 240-2600 nm range. FT-IR spectra
were measured in KBr pellets with a Perkin-Elmer 1000 Series
spectrometer (400-7800 cm-1). A Quantum Design MPMS-XL
SQUID magnetometer was used to measure static magnetic
susceptibilities of 1 and 5 from 1.9 up to 300 K and for 5 from
300 down to 4 K at a 100 mT static magnetic field. A sample holder
contribution (Θ) and core temperature independent diamagnetic
susceptibility (ø0) were subtracted from the experimental values.
The values of Θ and ø0 were calculated for 1 and 5 using the
appropriate formula: øM ) C/(T - Θ) + ø0. Two temperature
ranges (before and after the transition) were used in the calculations
for 5 (from 20 to 120 K and from 160 to 300 K). EPR spectra
were recorded for 1 at room temperature (RT) and for 5 from RT
down to 4 K and from 4 K up to RT with a JEOL JES-TE 200
X-band ESR spectrometer equipped with a JEOL ES-CT470
cryostat. Both slow cooling and heating were carried out within
4-6 h, whereas fast cooling was carried out only within 10 min
from RT down to 100 K.
1. Synthesis. Composition, elemental analysis of 1-4 are
listed in Table 1. 1 was obtained by the evaporation of a
chlorobenzene solution containing equimolar amounts of C60
(11) Konarev, D. V.; Kovalevsky, A. Yu.; Li, X.; Neretin, I. S.; Litvinov,
A. L.; Drichko, N. V.; Slovokhotov, Yu. L.; Coppens, P.; Lyubovskaya,
R. N. Inorg. Chem. 2002, 41, 3638.
(12) Jian, F.; Wang, Z.; Bai, Z.; You, X.; Fun, H.-K.; Chinnakali K.; Razak,
I. A. Polyhedron 1999, 18, 3401.
(13) Semkin, V. N.; Drichko, N. V.; Kimzerov, Yu. A.; Konarev, D. V.;
Lyubovskaya, R. N.; Graja, A. Chem. Phys. Lett. 1998, 295, 266.
(14) Picher, T.; Winkler, R.; Kuzmany, H. Phys. ReV. B 1994, 49, 15879.
(15) Fritz, H. P.; Lu¨ttke, W.; Stammreich, H.; Forneris, R. Chem. Ber. 1959,
92, 3246.
(16) Treichel, P. M.; Essenmacher, G. P.; Efner, H. F.; Klabunde, K. J.
Inorg. Chim. Acta 1981, 48, 41.
(17) Dubois, D.; Kadish, K. M.; Flanagan, S.; Haufler, R. E.; Chibante, L.
P. F.; Wilson, L. J. J. Am. Chem. Soc. 1991, 113, 4364.
(18) Dresselhaus, M. S.; Dresselhaus, G. In Fullerene Polymers and
Fullerene Polymer Composites; Eklund, P. C., Rao, A. M., Eds.;
Springer-Verlag; Berlin, 1999; pp 1-57.
(19) Rowland, R. S.; Taylor, R. J. Phys. Chem. 1996, 100, 7384.
(20) Elschenbroich, C.; Bilger, E.; Koch, J. J. Am. Chem. Soc. 1984, 106,
4297.
Crystal Structure Determination. Crystal data for 5:
(21) (a) Lokaj, J.; Vrabel, V.; Kello. E. Chem. ZVesti 1984, 38, 313. (b)
Riekkola, M.-L.; Pakkanen, T.; Niinisto, L. Acta Chem. Scand. Ser.
A. 1983, 37, 807.
(22) SMART and SAINTPLUS, Area detector control and integration
software, Version 6.01; Bruker Analytical X-ray Systems: Madison,
WI, 1999.
(23) SHELXTL, An integrated system for solving, refining and displaying
crystal structures from diffraction data, Version 5.10; Bruker Analytical
X-ray Systems: Madison, WI, 1997.
C
174H52N2S4Cr2Pd, Mr ) 2508.82, black needles, triclinic, space
group P1h. The unit cell parameters are a ) 10.182(2) Å, b )
15.225(3) Å, c ) 18.331(3) Å, R ) 65.837(3)°, â ) 74.733(3)°, γ
) 76.867(3)°, V ) 2478.1(8) Å3, Z ) 1, Dc ) 1.681 g‚cm-3, µ )
0.554 mm-1, F(000) ) 1268.0.
X-ray diffraction data for 5 were collected at 90(1) K using a
Bruker SMART1000 CCD diffractometer installed at a rotating
Inorganic Chemistry, Vol. 44, No. 25, 2005 9549

Konarev et al.
Table 2. UV-Vis-NIR Spectra of the Starting Compounds and 1-5
absorption bands, nma
M(dbdtc)2
•-
compounds
fullerene
NIR range (C60
)
C60
266s, 344, 470m, 605w
Cu(dbdtc)2
Ni(dbdtc)2
275s, 436s
326s, 635m
427m
∼670w
Cu(dbdtc)2‚C60‚0.5(C6H5Cl) (1)
Ni(dbdtc)2‚C60‚0.5(C6H5Cl) (2)
Pd(dbdtc)2‚C60‚0.5(C6H5Cl) (3)
Pt(dbdtc)2‚C60‚0.5(C6H5Cl) (4)
[Cr(C6H6)2]‚(C60)‚0.5[Pd(dbdtc)2] (5)
262s, 337s, -
260s, 337s, 485w, 610w
261s, 340s, 480w, 610w
261s, 340s, 480w, 610w
266s, 354s, -, 610w
933, 1073m
a s, strong; m, medium; w, weak.
and Cu(dbdtc)2, whereas solvate with chlorobenzene (C60‚
(C6H5Cl)x) was isolated in similar conditions with Ni(dbdtc)2,
Pd(dbdtc)2, and Pt(dbdtc)2 according to the IR spectra. The
crystallization of 2-4 was provided by an addition of an
excess of ferrocene, which however, was not inserted into
the crystals precipitated. Previously, it was found that the
excess of ferrocene provided the crystallization of solvent-
free phases without ferrocene or new phases of fullerene
complexes with ferrocene.11 In the case of 2-4, ferrocene
probably promoted the decomposition of a fullerene solvate
with chlorobenzene and, consequently, the formation of
complexes with M(dbdtc)2.
the generation of free charge carriers in [Cu(dedtc)2]2‚C60.9
Therefore, the absorption of a donor component in the visible
range is one of important factors, which define photocon-
ductivity in solid fullerene complexes. Since Ni(dbdtc)2
absorbs in the visible range with a maximum at 635 nm, the
absorption of 2 at ∼670 nm was also attributed to Ni(dbdtc)2.
Pd(dbdtc)2 and Pt(dbdtc)2 do not have noticeable absorption
in the visible range.
Ni(dbdtc)2, Pd(dbdtc)2, and Pt(dbdtc)2 are EPR silent, and
only CuII(dbdtc)2 with a 1/2 ground state is paramagnetic
and EPR active. Pristine Cu(dbdtc)2 has an asymmetric EPR
spectrum, which was simulated by two Lorentzian lines with
g1) 2.0515 and g2 ) 2.0295 and line halfwidths (∆H) of
8.52 and 5.76 mT. The EPR signal of 1 is also asymmetric
and was simulated by two Lorentzian lines with g1) 2.0521
and g2 ) 2.0362 and ∆H of 4.32 and 2.18 mT (Supporting
Information). The formation of a complex with C60 results
in the narrowing of the EPR signal (by a factor of 2-2.5)
with the retention of the g-factor values. This implies that
the environment of CuII centers in Cu(dbdtc)2 only weakly
changes in 1 relative to the pristine donor. The changes in
the EPR spectrum are more pronounced on the formation of
[Cu(dedtc)2]2‚C60.9 The EPR spectrum becomes a three-
component instead of a two-component one of pristine donor.
Such changes were attributed to the elongation of the axial
Cu-S bond in the dimer due to the appearance of weak axial
coordination of CuII to the C60 molecules.9 Magnetic
susceptibility of 1 follows the Curie-Weiss law, with a small
Weiss constant of 0.15 K showing the absence of a magnetic
interaction between CuII centers due to their large spatial
separation. This agrees with the planar monomeric state of
Cu(dbdtc)2 in 1. Dimeric CuII dialkyldithiocarbamates have
a stronger antiferromagnetic interaction between CuII cen-
ters.12
3. Ionic Multicomponent Complex [CrI(C6H6)2•+]‚(C60•-)‚
0.5[Pd(dbdtc)2] (5). 3.1. IR- and UV-Visible-NIR Spec-
tra. Three components were observed in the IR spectrum of
5 in KBr pellets. The absorption bands of C60 are positioned
at 526, 575, 1182 cm-1, and the split band has the maxima
at 1387, 1392, and 1396 cm-1. The F1u(4) mode of C60, which
is most sensitive to charge transfer to the C60 molecule is
shifted from 1429 to 1387, 1392 and 1396 cm-1, indicating
charge transfer of ∼1 electron to the C60 molecule. The
splitting of this mode can be due to the freezing of C60
molecular rotation even at RT and the decrease of its local
symmetry. Similar splitting was observed due to the similar
To prepare [Cr(C6H6)2•+]‚(C60•-)‚0.5[Pd(dbdtc)2] (5) (Table
1), we used slow diffusion, in which Cr(C6H6)2, C60 and the
excess of Pd(dbdtc)2 dissolved in C6H4Cl2 were covered by
hexane. In these conditions, 5 was formed instead of
previously obtained Cr(C6H6)2‚C60‚0.7(C6H4Cl2).5f Cu(dbdtc)2
was not used in the synthesis because of the reduction of
CuII to CuI by Cr(C6H6)2, which was accompanied by the
color change from dark-brown to light-yellow characteristic
of a CuI complex. Despite similar sizes and shapes, M(dbdtc)2
and TBPDA form multicomponent complexes of different
types. The (D+)‚(C60•-)‚2(TBPDA) complexes have large
cavities to accommodate Cp*2Cr+, Cp*2Co+, or TDAE•+
•+
cations, whereas smaller CrI(C6H6)2 and Cp2Co+ (cobal-
tocenium) do not form such complexes.10e In contrast,
•-
Pd(dbdtc)2 forms a complex with C60 only together with
•+
CrI(C6H6)2 countercations.
2. Neutral Complexes 1-4. The IR spectra of 1-4 are a
superposition of those of C60, M(dbdtc)2, and C6H5Cl
molecules (Supporting Information). IR-active bands of C60
at 527, 577, 1182, and 1429 cm-1 remain almost unchanged
in the complexes (526, 577, 1182, and 1427-1428 cm-1),
showing no noticeable charge transfer to C60 in the ground
state. The bands of M(dbdtc)2 are shifted up to 10 cm-1
relative to starting donors, showing the changes in geometry
of the M(dbdtc)2 molecules in the complexes rather than
charge transfer. The UV-visible-NIR spectra also justify
a neutral ground state of the complexes (Table 2). The bands
at 933 and 1073 nm characteristic of the C60 monoanion3
are absent in the spectra of 1-4. Cu(dbdtc)2 has absorption
with a maximum at 436 nm and the absorption tail up to
600 nm. This absorption is still observed in the spectrum of
1 at 427 nm (Table 2). A similar absorption spectrum was
reported for [Cu(dedtc)2]2‚C60 with a maximum at 442 nm.9
Photoexcitation of Cu(dedtc)2 was shown to contribute to
9550 Inorganic Chemistry, Vol. 44, No. 25, 2005

Complexes of C60 with Metal Dibenzyldithiocarbamates
•-
Figure 2. View of the crystal structure of 5 on the ac plane. One of the pairs from two C60 radical anions is shown by the solid parallelogram. The
shortest interfullerene C‚‚‚C contact in the pair is depicted by a dashed line.
reason for some neutral complexes of C60.13 The integral
intensity of the band at 575 cm-1 is essentially higher than
and Pd(dbdtc)2 layers in the voids formed by two Pd(dbdtc)2
molecules and four C60 radical anions (Figure 2).
•-
that of the band at 526 cm-1. This is also characteristic of
Within a fullerene layer, the pairs of C60•- can be outlined
(solid parallelogram in Figure 2) with a center-to-center
interfullerene distance of 10.16 Å. There is one shortened
van der Waals interfullerene C‚‚‚C contact of 3.092(2) Å in
the pairs (dashed line in Figure 2). This contact is essentially
longer than the intercage C-C bond in the (C60-)2 dimer
(1.597 Å5e). However, it is noticeably shorter than the sum
of van der Waals radii of two carbon atoms (3.42 Å19). In
•- 14
C60
. The bands at 419, 458, 787, 815, 971, 1011, 1140,
and 1263 cm-1 were attributed to Cr(C6H6)2. Two bands of
Cr(C6H6)2 are sensitive to charge transfer and are shifted from
459 and 490 cm-1 in the neutral state to 419 and 460 cm-1
in ionic (CrI(C6H6)2•+)(I-).15 Similar shifts of the bands in
the spectrum of 5 (419 and 458 cm-1) also indicate the
formation of CrI(C6H6)2•+ radical cations, which is possible
due to that the first redox potential of Cr(C6H6)2 (E+/0 )
-0.72 V vs SCE16) is more negative than that of C60 (E0/-
) -0.44 V vs SCE17). The remaining absorption bands were
attributed to Pd(dbdtc)2 (Supporting Information). The UV-
visible-NIR spectrum of 5 (Table 2) justifies the formation
of C60•- from characteristic bands at 933 and 1073 nm. The
additional bands in IR and UV-visible-NIR ranges, which
•-
addition to adjacent fullerenes in the pair, each C60 has
•-
another four neighboring C60 radical anions within the
layer. Two neighbors are positioned on the same level along
the a direction (Figure 2) with a center-to-center distance of
10.18 Å, and the shortest interfullerene C‚‚‚C contacts are
in the 3.69-3.76 Å range (longer than 3.42 Å). Two other
neighbors are positioned approximately along the c axis with
a center-to-center distance of 9.92 Å. However, the shortest
C‚‚‚C contacts (3.39-3.75 Å) are noticeabely longer than
the interfullerene C‚‚‚C distance in the pairs (Figure 2).
must accompany the dimerization or polymerization of
•-18
C60
are absent, indicating their monomeric state at RT.
3.2. Crystal Structure. The crystal structure of 5 was
determined at 90 K. It should be noted that a single crystal
to be measured was cooled very fast from RT down to 90 K
•+
Each fullerene pair is surrounded by four CrI(C6H6)2
radical cations, which form shortened van der Waals C‚‚‚C
and H‚‚‚C contacts in the 3.23-3.56 and 2.65-2.92 Å ranges
•-
(within 10 s). The complex has a triclinic lattice. C60
,
CrI(C6H6)2•+, and Pd(dbdtc)2 are completely ordered at 90
•-
(Figures 2 and 3). The C60 radical anions from one pair
•-
•+
K; C60 and CrI(C6H6)2 radical ions occupy general
positions, while Pd(dbdtc)2 is located in a special position
with the Pd atom being on a center of symmetry.
form van der Waals C‚‚‚C contacts (3.30-3.50 Å) with
benzyl groups of two Pd(dbdtc)2 molecules lying above and
below a fullerene layer (dashed lines in Figure 3). The central
PdS4 fragment does not form any shortened contacts with
The complex has layered packing, in which strongly
puckered layers of C60•- alternate with the layers composed
of neutral Pd(dbdtc)2 molecules along the b direction (Figure
•-
•+
C60 and CrI(C6H6)2 radical ions; therefore, PdII(dbdtc)2
does not coordinate to C60 in contrast to CoIITPP, which
forms diamagnetic σ-bonded (CoIITPP‚fullerene-) anions.10a
•-
•+
•-
2). CrI(C6H6)2 radical cations are arranged between C60
Inorganic Chemistry, Vol. 44, No. 25, 2005 9551

Konarev et al.
Figure 5. The changes in the integral intensity of the EPR signal of 5 on
slow cooling and heating.
Figure 3. Van der Waals contacts in the crystal structure of 5 between
•+
Pd(dbdtc)2, C60•-, and Cr(C6H6)2 radical ions (dashed lines).
Figure 6. The splitting of the EPR signal from 5 upon the dimerization
•-
of C60 in the 150-110 K range on slow cooling.
3.4. Peculiarities of the Formation of (C60-)2 Dimers
in 5. The magnetic moment of 5 is only weakly temperature
dependent on slow cooling (within 4-6 h) from RT down
to 150 K and below 150 K decreases down to 1.62 µB (130
K) (Figure 4). This value is close to the contribution of one
1/2 spin per formula unit (1.73 µB). Above and below the
transition, magnetic susceptibility of 5 follows the Curie-
Weiss law with small Weiss constants (-0.3 and 0.2 K,
respectively). EPR measurements are in agreement with
SQUID data. The EPR signal remains unchanged down to
150 K (g ) 1.9929 and ∆H ) 3.61 mT). The integral
intensity of the EPR signal abruptly decreases by a factor of
2 at 150-120 K (Figure 5) and the signal splits into two
lines with g1 ) 1.9960 (∆H ) 2.24 mT) and g2 ) 1.9826
(∆H ) 2.32 mT) at 120 K (Figure 6). Two lines have nearly
temperature independent g-factors and line halfwidths down
to 4 K (g1 )1.9967 and g2 )1.9839 with ∆H ) 2.33 and
Figure 4. Effective magnetic moment on slow cooling 5 in the 300-1.9
K range. The insert shows the magnetic hysteresis in the 100-200 K range.
The central (NCS2)2Pd fragment of the Pd(dbdtc)2 mol-
ecule is planar (the dihedral angle between two NCS2Pd
planes is 180°). The averaged lengths of the S-Pd bonds
are 2.325 Å.
3.3. Magnetic Properties of 5. The complex manifests a
symmetric Lorentzian EPR signal at RT with g ) 1.9934
and a line halfwidth (∆H) of 4.06 mT. This signal has a
g-factor intermediate between those characteristic of
•+
monomeric C60•- (g ) 1.9996-2.0000)1b,1c and CrI(C6H6)2
(g ) 1.9860)20 and was attributed to a resonating signal
between these radical ions due to direct exchange coupling.
Similar resonating EPR signals were observed in monomeric
high-temperature phases of Cr(C6H6)2‚C60‚0.7(C6H4Cl2) and
Cr(C6H6)2‚C60‚C6H5CN,5e as well as in ionic complexes of
C60 with other substituted bis(arene)chromium compounds.5d,5g
The RT magnetic moment of 5 is 2.26 µB (Figure 4). This
value is close to 2.45 µB (the value estimated for the system
of two 1/2 spins per formula unit), implying the contribution
2.34 mT), justifying the attribution of this signal to
•+ 20
CrI(C6H6)2
. A similar signal was observed in a dimeric
phase of Cr(C6H6)2‚C60‚C6H5CN below 160 K (g1 ) 1.9949
and g2 ) 1.9835 at 4 K), whereas the signal in a dimeric
phase of Cr(C6H6)2‚C60‚0.7(C6H4Cl2) is a single Lorentzian
line down to 4 K.5e Thus, below 120 K, spins in 5 are
localized on CrI(C6H6)2•+ and the transition is associated with
•-
•+
from both C60 and CrI(C6H6)2 radical ions.
9552 Inorganic Chemistry, Vol. 44, No. 25, 2005

Complexes of C60 with Metal Dibenzyldithiocarbamates
absorption in the visible range, their complexes with C60 can
be photoactive similarly to [Cu(dedtc)2]2‚C60,9 and now this
work is in progress. Ionic [CrI(C6H6)2•+]‚(C60•-)‚0.5[Pd(dbdtc)2]
•-
(5) contains neutral Pd(dbdtc)2, C60 radical anions, and
•+
CrI(C6H6)2 radical cations. The crystal structure of 5 (90
K) reveals layered packing with the alternation of strongly
•+
puckered C60•- layers with those of Pd(dbdtc)2. CrI(C6H6)2
radical cations are arranged between the layers (Figure 2).
•-
The radical anions form pairs within the C60 layers with
the shortest interfullerene C‚‚‚C contact of 3.092(2) Å (Figure
•-
2). Thus, C60 radical anions are monomeric at 90 K.
However, they can dimerize in the direction of this contact
within the pairs. SQUID and EPR measurements indicate
the formation of (C60-)2 dimers below 150-130 K on slow
cooling and their dissociation above 150-170 K on heating
(Figures 4 and 5). A symmetric EPR signal with g ) 1.9934
•-
attributable to a resonating signal between C60 and
CrI(C6H6)2 radical ions changes to an asymmetric EPR
•+
Figure 7. The EPR spectrum of 5 (100-4 K) upon fast cooling from RT
down to 100 K.
signal with two lines with g1 ) 1.9959 and g2 ) 1.9830
•+
characteristic of isolated CrI(C6H6)2 (Figure 6). The dis-
the reversible formation of diamagnetic and EPR-silent
single-bonded (C60-)2 dimers. Spin and magnetic susceptibil-
ity measurements on slow heating indicate the transition to
be reversible with the shift to higher temperatures (150-
170 K). Therefore, the hysteresis is 20 K (Figure 4, insert,
and Figure 5). The crystals of 5 were also fast cooled from
RT down to 100 K (within 10 min). In this case, the EPR
signal indicates the retention of the monomeric phase even
at 100 K (g ) 1.9930 and ∆H ) 3.87 mT) (Figure 7). The
signal remains unchanged down to 60 K (Figure 7) and only
below 60 K splits into two components (g1 ) 1.9991 and
∆H ) 2.38 mT and g2 ) 1.9826 and ∆H ) 2.39 mT at 4
K), suggesting the dimerization of C60•-. Similar splitting is
observed upon the dimerization of C60•- on slow cooling of
5 in the range 150-120 K (Figure 6). Thus, fast cooling
essentially lowers dimerization temperature.
sociation temperature for the (C60-)2 dimers in 5 and their
stability are low in comparison with those for other ionic
complexes of C60 (160-250 K).5d-g Two peculiarities were
found for such low-temperature dimerization. The dimer-
ization in 5 has a larger hysteresis of 20 K, whereas in
Cp*2Cr‚C60‚(C6H4Cl2)2 with the dimerization temperature
above 200 K, the hysteresis was smaller than 2 K.5e Fast
cooling from RT down to 100 K completely suppresses
dimerization, and according to EPR, it is observed only below
60 K (Figure 7). The crystal for a X-ray diffraction experi-
ment was fast cooled from RT down to 90 K, and this can
be a reason for the retention of a monomeric phase of 5 at
90 K.
Acknowledgment. The work was partly supported by a
Grant-in-Aid Scientific Research from the Ministry of
Education, Culture, Sports, Science and Technology, Japan
(152005019, 21st Century COE, and Elements Science
12CE2005) and the RFBR Grant No. 03-03-32699a.
Conclusion
In contrast to the C60 complex with butterfly-shaped [Cu-
(dedtc)2]2 dimers,9 different M(dbdtc)2 (M ) CuII, NiII, PdII,
and PtII) most probably form complexes with C60 (1-4) in
planar conformation of the central (NCS2)2M fragment
adopting to spherical C60 molecules by flexible benzyl
substituents. Planar conformation is known to be peculiar
for Ni(dbdtc)2, Pd(dbdtc)2, and Pt(dbdtc)221 and can also be
realized for Cu(dbdtc)2 due to the repulsion of bulky benzyl
substituents. Two of the four dibenzyldithiocarbamates have
Supporting Information Available: Crystallographic data in
CIF format for 5, data of IR spectra for starting compounds and
1-5 (Table 1), UV-visible-NIR spectra for complexes 1-3 and
5, and EPR spectra for 1 and Cu(dbdtc)2 (Figures 1-5). This
material is available free of charge via the Internet at http://
pubs.acs.org.
IC051261I
Inorganic Chemistry, Vol. 44, No. 25, 2005 9553