Brief Communications: Crystal structures of molecular complexes of fullerene C60 with tetraphenylsilane and tetraphenylgermane

Article abstract of DOI:10.1007/s11172-009-0138-8

New molecular complexes of fullerene C₆₀ · Ph₄ E (E = Si, Ge, and Sn) were synthesized, and their crystal structures were determined. All molecular complexes are isostructural singlephase systems. The planes of the benzene rings in t

Full text of DOI:10.1007/s11172-009-0138-8

Russian Chemical Bulletin, International Edition, Vol. 58, No. 5, pp. 1084—1087, May, 2009
1084
Brief Communications
Crystal structures of molecular complexes of fullerene C60
with tetraphenylsilane and tetraphenylgermane
O. N. Suvorova, V. V. Kutyreva, G. K. Fukin, E. V. Baranov, A. I. Kirillov, and E. A. Shchupak
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhnii Novgorod, Russian Federation.
Fax: +7 (831) 462 7497. Eꢀmail: suvor@iomc.ras.ru
New molecular complexes of fullerene C60•Ph4E (E = Si, Ge, and Sn) were synthesized,
and their crystal structures were determined. All molecular complexes are isostructural singleꢀ
phase systems. The planes of the benzene rings in the Ph4E molecules are virtually parallel to
the sixꢀmembered fragments of the fullerene molecule.
Key words: Xꢀray diffraction study, fullerene, tetraphenylsilane, tetraphenylgermane,
tetraphenylstannane, molecular complex, structure.
Neutral molecular complexes of fullerene with πꢀdonor
sized new molecular complexes of fullerene C60 with
tetraphenylsilane, tetraphenylgermane, and tetraphenylꢀ
stannane. The crystal structure of Ph4Si, Ph4Ge, and
Ph4Sn6 is a tetragonal lattice containing a Si (Ge or Sn)
atom at the origin of coordinates surrounded by four benꢀ
zene rings in such a way that there are threeꢀdimensional
cavities between the molecules, which can be occupied by
fullerene molecules. In the crystal lattices of the starting
tetraphenylꢀsubstituted derivatives Ph4E, these cavities are
partially occupied by the phenyl ligands of the adjacent
molecules.
The singleꢀcrystal Xꢀray diffraction study of the
molecular complexes C60·Ph4E (E = Si (1) and Ge (2))
showed that complexes 1 and 2 are isostructural. In the
crystal structures, the fullerene and Ph4E molecules are
located on a fourfold axis (Fig. 1).
organic and organometallic compounds have attracted
attention because these complexes have wide applicaꢀ
tion in the synthesis of new composite and functional
materials.1—5
The physical properties of these complexes are greatly
determined by their structure. The packing of fullerene
molecules and the distances between the molecules in the
crystal structures depend on the structure and properties
of the incorporated donor molecules. Hence, to prepare
materials with desired properties based on molecular comꢀ
plexes of fullerene, it is of importance to know the strucꢀ
tural features of these compounds.
In the present study, to examine the possibility of
preparing composite materials based on fullerene and
organic compounds of Group 14 elements, we syntheꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1056—1059, May, 2009.
1066ꢀ5285/09/5805ꢀ1084 © 2009 Springer Science+Business Media, Inc.

Crystal structure of C60•Ph4E complexes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1085
the fullerene molecules. An increase in the As—C(Ph)
distances by 0.095 Å compared to the P—C(Ph) distances
leads to a shortening of the distances between the centers
of the benzene rings of the Ph4As molecules and the cenꢀ
ters of the sixꢀmembered fragments of the fullerene molꢀ
ecules by 0.008 Å. Since the benzene rings of the Ph4E
molecules are parallel to the hexagonal fragment of the
adjacent fullerene molecules, the Ph4E and C60 molecules
in the crystal structures of compounds 1 and 2 are arꢀ
ranged in a herringbone fashion parallel to the ab plane
(Fig. 2, a). The layers consisting of the Ph4E and C60
molecules alternate in the projection onto the ac plane
perpendicular to the herringbone packing, the layer of C60
molecules having a zigzag shape (Fig. 2, b).
We failed to grow single crystals of C60•Ph4Sn (3)
suitable for Xꢀray diffraction study. Hence, we studied
compounds 1—3 by Xꢀray powder diffraction. Figure 3
represents the Xꢀray diffraction patterns of compounds
1—3, which show that all molecular complexes of fullerene
with the tetraphenylꢀsubstituted derivatives Ph4E (E = Si,
Ge, or Sn) are isostructural individual phases.
C(4)
C(9)
C(20)
C(19)
C(8)
C(7)
C(5)
C(6)
C(21)
C(18)
C(22)
C(17)
E
Therefore, we demonstrated for the first time that it is
possible to synthesize stable molecular complexes of
fullerene C60 with organosilicon, ꢀgermanium, and ꢀtin
compounds. The introduction of fullerene molecules into
Fig. 1. Structural fragment of complexes 1 (E = Si) and 2
(E = Ge). Displacement ellipsoids are drawn at the 30% probꢀ
ability level. In the crystal structure, each benzene ring faces a
fullerene molecule.
Table 1. Principal crystallographic characteristics and the Xꢀray
data collection and refinement statistics for complexes 1 and 2
As a result, the fiveꢀ and sixꢀmembered fragments of
the fullerene molecules are disordered about the fourfold
axis. It should be noted that all benzene rings in the Ph4E
molecules are virtually parallel to the sixꢀmembered moiꢀ
eties of the fullerene. The corresponding dihedral angle is
9.1° and 9.9° for compounds 1 and 2, respectively. The
distances between the centers of the benzene rings of the
Ph4E molecules and the corresponding fragments of the
fullerene molecules are 3.806 and 3.796 Å in 1 and 2,
respectively. It is interesting that an increase in the
Ge—C(Ph) distances (1.9514(13) Å) by 0.076 Å comꢀ
pared to the Si—C(Ph) distances (1.8751(13) Å) leads to
a shortening of the distances between the centers of the
benzene rings of the Ph4Ge molecules and the centers of
the sixꢀmembered fragments of the fullerene molecules
by 0.01 Å. The shortest distance between the center of the
benzene ring and the C(5) atom of the fullerene molecule
is 3.460 and 3.451 Å in compounds 1 and 2, respectively.
Apparently, this is indirect evidence of the attractive inꢀ
teractions between the πꢀsystem of the phenyl ring and
the fullerene molecule. If repulsive interactions between
these moieties dominate, the corresponding distances
would be slightly larger or would change in proportion to
the E—C(Ph) bond length. An analogous situation is obꢀ
served in the isostructural complexes C60·Ph4ECl, where
E is P (see Ref. 7) or As,8 in which the phenyl groups are
also virtually parallel to the sixꢀmembered fragments of
Parameter
1
2
Molecular formula
Molecular weight
Crystal system
Space group
a/Å
C84H20Si
1057.09
C84H20Ge
1101.59
Tetragonal
P4/n
12.5485(12)
14.1432(14)
2227.1(4)
2
12.5659(2)
14.2098(4)
2243.75(8)
2
1.631
0.745
c/Å
V/Å3
Z
dcalc/g cm–3
1.576
0.116
1076
μ/mm–1
F(000)
1112
Crystal dimensions/mm
θꢀAngle range/deg
hkl Ranges
0.27×0.19×0.10 0.25×0.15×0.08
2.71—26.99
–16 ≤ h ≤ 15
–16 ≤ k ≤ 16
–18 ≤ l ≤ 18
1.62—27.49
–16 ≤ h ≤ 16
–14 ≤ k ≤ 16
–18 ≤ l ≤ 16
Number of reflections:
observed
independent
19870
2421
0.1444
0.942
15082
2562
0.0312
1.006
Rint
Goodnessꢀofꢀfit (F2)
R1/wR2 (I > 2σ(I))
R1/wR2
0.0524/0.1040 0.0367/0.0880
(based on all reflections)
Residual electron density
(ρmax/ρmin)/e•Å–3
0.1045/0.1172 0.0442/0.0916
0.272/–0.351
0.351/–0.254

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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Suvorova et al.
c
a
0
b
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
E
E
Ph
Ph
a
Ph
Ph
E
Ph
Ph
b
b
c
Ph
Ph
Ph
Ph
E
Ph
Ph
E
Ph
Ph
E
Ph
Ph
E
Ph
Ph
Ph
Ph
Ph
Ph
a
Ph
Ph
Ph
Ph
Ph
Ph
E
E
Ph
Ph
Fig. 2. Crystal packing of complexes 1 and 2 projected onto the planes ab (a) and ac (b).
Experimental
the tetragonal lattice of Ph4E results in the tetrahedral
arrangement of the fullerene molecules with respect to
Fullerene with a purity of 99.5% was purchased from the
Fullerene Center (Nizhnii Novgorod). Benzene was purified by
distillation over sodium under an argon flow. Tetraphenylsilane
and tetraphenylgermane were synthesized according to known
procedures.9,10
Complexes C60•EPh4 (E = Si, Ge, Sn) were prepared by
crystallization using the slow diffusion of a saturated benzene
solution of fullerene C60 into a saturated benzene solution of
Ph4E. The tetrahedral arrangement of the C60 molecules
about Ph4E is apparently determined by weak π—π interꢀ
actions between the benzene ring and the hexagonal fragꢀ
ment of C60, which is indirectly evidenced by the virtually
parallel orientation of these sixꢀmembered fragments acꢀ
cording to the Xꢀray diffraction data for the crystals of
compounds 1 and 2.

Crystal structure of C60•Ph4E complexes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1087
I
diffraction patterns (see Fig. 3), the lines of the starting
compounds were absent, and the products were indexed as a
tetragonal phase with the criterion M20 > 100. The refinement
of the peak profiles and the lattice parameters by the fullꢀprofile
analysis (see Fig. 3, a) for the space group P4/n gave the following
unit cell parameters: a = 12.682 Å, c = 14.355 Å for complex 1,
a = 12.699 Å, c = 14.411 Å for complex 2, and a = 12.722 Å,
c = 14.413 Å for complex 3. Some discrepancy between the unit
cell parameters determined based on the powder and singleꢀ
crystal Xꢀray diffraction data is attributed to the difference in
the temperature of the Xꢀray data collection.
1
10 15 20 25 30 35 40 45
2θ/deg
I
2
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos 06ꢀ03ꢀ32728a
and 08ꢀ0397054) and the Council on Grants of the President
of the Russian Federation (Program for State Support of
Leading Scientific Schools of the Russian Federation, Grant
NShꢀ1396.2008.3 and State Contract No. 02.513.11.0002).
10 15 20 25 30 35 40 45
2θ/deg
I
3
References
10 15 20 25 30 35 40 45
2θ/deg
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Fig. 3. Results of the refinement for C60•Ph4Si (1) and the
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C60•Ph4Sn (3).
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Received October 22, 2008;
in revised form January 14, 2009