1,2ꢀ(CMe2CN)(H)C60 and [1,2ꢀ(CMe2CN)(H)C60]–• Russ.Chem.Bull., Int.Ed., Vol. 57, No. 9, September, 2008
1973
sistency between the spectral characteristics obtained by 1H and
13C NMR spectroscopy and by electronic spectroscopy and the
published data.11 Since fullerene and its derivatives are prone to
incomplete combustion during elemental analysis,2 the compoꢀ
sitions of the compounds synthesized were confirmed by the
weight loss data of thermogravimetric and thermal decomposiꢀ
tion studies and by the compositions of the volatiles and the solid
residue of the decomposition. The weight loss of sample 1 on
heating to 673 K is due to the detachment of the [CMe2CN]
fragments from fullerene, which remained in the solid residue.
The weight loss was 15.03%, which agrees well with a calculated
value of 15.89%.
position in vacuo (10–2 Torr) of 2 on heating (T > 513 K) is
a mixture of substances 5, 6, and 7. Substance 1 begins
to decompose under atmospheric pressure or in vacuo
(10–2 Torr) above 513 K. The volatile products of its deꢀ
composition are compounds 5, 6, and 7. Salt 3 begins to
decompose in vacuo (10–2 Torr) at T > 363 K. Therefore,
neutral substance 1 loses the 2ꢀcyanoisopropyl fragments
at a higher temperature than salt 3, and the [Ful]—[R]
bond (Ful is fullerene) in the (1,4ꢀR2C60)–• radical anion
is weaker than that in the corresponding neutral fullerene
derivative 1,4ꢀR2C60 (R is 2ꢀcyanoisopropyl). The seꢀ
quence of reactions including the decomposition of the
radicalꢀion salts [(arene)2Cr]+•[1,4ꢀR2C60]–• in THF soꢀ
lution with the formation of (RC60)– anions followed by
protonation of the latter is a new synthetic route to the
fullerene derivatives 1,2ꢀ(R)(H)C60.
Bis(biphenyl)chromium(0) was synthesized according to
a previously described procedure.5
Bis(biphenyl)chromium(I) 1,4ꢀdi(2ꢀcyanoisopropyl)ꢀ1,4ꢀdiꢀ
–•
hydrofulleride [(Ph2)2Cr]+•[1,4ꢀ(CMe2CN)2C60
]
(3). An exꢀ
cess of (Ph2)2Cr0 was added to a saturated solution of 1 in toluꢀ
ene, and the mixture was stirred for 30 min. A half of the solvent
volume was removed in vacuo, and the rest amount was decantꢀ
ed. The brown precipitate of 3 was thoroughly washed with hexꢀ
ane and dried in vacuo at ~20 °С. The yield was 50% based on
compound 1. Found (%): Сr, 4.35. C92H32CrN2. Calculated (%):
Сr, 4.28.
Experimental
The synthesis and studies of the properties of the substances
were carried out in evacuated ampules (no trace oxygen and
water were present). The solvents were purified and dehydrated
according to standard procedures and degassed before experiꢀ
ments using three freezingꢀdefreezing cycles in vacuo.
Thermal decomposition of the compounds was studied in
sealed glass apparatuses evacuated to 10–2 Torr. Volatile prodꢀ
ucts were collected in a trap cooled with liquid nitrogen.
ESR spectra were obtained on a Bruker EPX spectrometer.
IR spectra were recorded on an FSM 1201 FTIR spectromeꢀ
ter at 293 K in Nujol.
1H NMR spectra were recorded on a Bruker DPXꢀ200 inꢀ
strument in CDCl3 and С6D6. The chemical shifts were meaꢀ
sured relative to Me4Si.
Electronic spectra were recorded on a Perkin—Elmer Lambꢀ
da 25 spectrometer.
Calculations of the Cr content in the compounds were based
on the amount of Cr2O3 remained after combustion.
Substance 1 was synthesized by a modified procedure.11 The
synthesis temperature was increased from 348 to 398 K in order
to increase the content of 1,4ꢀdi(2ꢀcyanoisopropyl)ꢀ1,4ꢀdihyꢀ
drofullerene, which should be more stable than 1,2ꢀdi(2ꢀcyꢀ
anoisopropyl)ꢀ1,4ꢀdihydrofullerene. oꢀDichlorobenzene, a solꢀ
vent of relatively high polarity for chromatography, was removed
in vacuo after the synthesis. This made it possible to considerably
simplify the chromatographic procedure.
Bis(biphenyl)chromium(I) 1ꢀ(2ꢀcyanoisopropyl)ꢀ1,2ꢀdihydroꢀ
–•
fulleride [(Ph2)2Cr]+•[1,2ꢀ(CMe2CN)(H)C60
]
(4). An excess
of (Ph2)2Cr0 was added to a saturated solution of 2 in toluene,
and the mixture was stirred for 30 min. A half of the solvent
volume was removed in vacuo, and the rest amount was decantꢀ
ed. The brown precipitate of 2 was thoroughly washed with hexꢀ
ane and dried in vacuo at ~20 °С. The yield was 50% based on
compound 2. Found (%): Сr, 4.60. C88H27CrN. Calculated (%):
Сr, 4.53.
Bis(biphenyl)chromium(I)
(2ꢀcyanoisopropyl)fulleride
(8). A solution of complex 4 in
–•
[(Ph2)2Cr]+•[(CMe2CN)C60
]
THF was heated for 3 h at 335 K. The solvent was removed, and
the green crystalline residue was dried for 30 min in vacuo
(10–2 Torr) at 315 K, washed twice with toluene, then with hexꢀ
ane, and dried. The yield was 70% based on compound 4. Found (%):
Сr, 4.60. C88H26CrN. Calculated (%): Сr, 4.53.
1ꢀ(2ꢀCyanoisopropyl)ꢀ1,2ꢀdihydrofullerene
1,2ꢀ
(CMe2CN)(H)C60 (2). A solution of compound 3 in THF was
kept at 335 K for 3 h and then treated with an excess of HCl at
293 K. The solvent was removed in vacuo, the residue was washed
with hexane, dried, and dissolved in a minimum amount of toluꢀ
ene. The solution was filtered and chromatographed on a colꢀ
umn packed with Al2O3 in toluene (with toluene as the eluent),
and the second (redꢀbrown) fraction was collected. The solvent
was removed in vacuo and the residue was recrystallized from
benzene. The yield of compound 2 was 20% (based on comꢀ
pound 3). The weight loss of sample 2 on heating from 453 to
673 K is due to the detachment of the [CMe2CN] fragments and
hydrogen atoms from fullerene, which remained in the solid
residue. The weight loss was 8.00%, which agrees well with
a calculated value of 8.75%.
Single crystals of compound 2 were prepared by slow cooling
to 289 K of a saturated (at 323 K) solution of 2 diluted by two
times with deuterobenzene in an NMR tube.
Xꢀray studies. Xꢀray diffraction measurements of substance 2
were carried out on a SMART Apex diffractometer (graphite
diffractometer, θ—ω scan mode, MoꢀKα radiation). The crystals
of 2 are twinned. The structure of compound 2 was determined
1,4ꢀDi(2ꢀcyanoisopropyl)ꢀ1,4ꢀdihydrofullerene
1,4ꢀ
(CMe2CN)2C60 (1). A mixture of С60 (0.2 g), AIBN (0.1 g), and
oꢀdichlorobenzene (30 mL) was stirred in a sealed ampule for 1 h
at 398 K. The reaction mixture was cooled and filtered, and the
solvent was recondensed in vacuo (10–2 Torr). The residue was
washed with hexane, dried, and dissolved in a minimum amount
of toluene. The solution was filtered and placed in a chromatoꢀ
graphic column packed with Al2O3 in toluene. The substance
was eluted with toluene and the third fraction (green color) was
collected. Toluene was removed in vacuo (10–2 Torr) and the
residue was washed with hexane and dried in vacuo on a boiling
water bath. Compound 1 (0.05 g) was obtained as dark brown
powder, whose individual character was confirmed by the conꢀ