Franken et al.
Synthesis of [1,3,4,9-{MFe(CO)4(PPh3)}-1,3-(µ-H)2-9,9,9-
(CO)3-arachno-9,6-FeCB8H9]. (i) Compound 3 (0.23 g, 0.25
mmol), [CuCl(PPh3)]4 (0.09 g, 0.06 mmol), and Tl[PF6] (0.09 g,
0.25 mmol) were stirred in CH2Cl2 (10 mL) at room temperature
for ca. 18 h. The resulting mixture was filtered through Celite, and
the filtrate was evaporated to dryness in vacuo. The residue was
taken up in CH2Cl2 (2 mL) and applied to a chromatography
column. Elution with CH2Cl2-petroleum ether (1:1) gave an orange
fraction that was collected, evaporated in vacuo, and crystallized
from CH2Cl2-petroleum ether to give orange microcrystals of
[1,3,4,9-{CuFe(CO)4(PPh3)}-1,3-(µ-H)2-9,9,9-(CO)3-arachno-9,6-
FeCB8H9] (7; 0.16 g). (ii) Similarly, compound 3 (0.23 g, 0.25
mmol), Ag[PF6] (0.070 g, 0.25 mmol), and PPh3 (0.070 g, 0.25
mmol) yielded orange microcrystals of [1,3,4,9-{AgFe(CO)4-
(PPh3)}-1,3-(µ-H)2-9,9,9-(CO)3-arachno-9,6-FeCB8H9] (8; 0.16 g).
Synthesis of [4,9-(PEt3)2-9,9-(CO)2-nido-9,6-FeCB8H10]. Com-
pound 6 (0.10 g, 0.25 mmol) was dissolved in CH2Cl2 (10 mL),
PEt3 (0.25 mL, 0.20 g, 1.69 mmol) and Me3NO (0.075 g, 1.0 mmol)
were added, and the mixture was stirred at room temperature for
ca. 5 days. Volatiles were removed under reduced pressure, and
the residue was redissolved in CH2Cl2 (2 mL) and transferred to
the top of a chromatography column. Elution with CH2Cl2-
petroleum ether (4:1) gave a pink fraction from which removal of
solvent in vacuo and crystallization from Et2O (-30 °C) yielded
red microcrystals of [4,9-(PEt3)2-9,9-(CO)2-nido-9,6-FeCB8H10] (9;
0.050 g).
Experimental Section
General Considerations. All reactions were carried out under
an atmosphere of dry, oxygen-free dinitrogen using standard
Schlenk line techniques. Solvents were stored over and distilled
from appropriate drying agents under dinitrogen prior to use.
Petroleum ether refers to that fraction of boiling point 40-60 °C.
Chromatography columns (typically ca. 15 cm in length and ca. 2
cm in diameter) were packed with silica gel (Acros, 60-200 mesh).
NMR spectra were recorded at the following frequencies (MHz):
1H, 360.1; 13C, 90.6; 11B, 115.5; and 31P, 145.8. The compounds
[arachno-4-CB8H14],8 [NBun ][closo-4-CB8H9],8 and [CuCl-
4
27
(PPh3)]4 were prepared according to the literature; all other
materials were used as received.
Synthesis of [N(PPh3)2][4,9-{Fe(CO)4}-9,9,9-(CO)3-arachno-
9,6-FeCB8H11]. The compounds [Fe3(CO)12] (0.50 g, 1.0 mmol)
and [arachno-4-CB8H14] (0.056 g, 0.5 mmol) were dissolved in
THF (10 mL) and heated to reflux for 24 h. The mixture was cooled
to room temperature, and [N(PPh3)2]Cl (0.29 g, 0.5 mmol) was
added. Solvent was removed in vacuo, and the residue was dissolved
in CH2Cl2 (2 mL) and transferred to the top of a chromatography
column. Elution with CH2Cl2-petroleum ether (4:1) gave a yellow
fraction from which was obtained, after removal of solvent in vacuo
and then crystallization from CH2Cl2-petroleum ether, yellow
microcrystals of [N(PPh3)2][4,9-{Fe(CO)4}-9,9,9-(CO)3-arachno-
9,6-FeCB8H11] (3; 0.23 g).
Synthesis of [N(PPh3)2][2,2,2-(CO)3-closo-2,1-FeCB8H9]. Com-
pound 3 (0.23 g, 0.25 mmol) was dissolved in toluene (10 mL)
and heated to reflux for 4 h. Volatiles were removed in vacuo, and
the residue was dissolved in CH2Cl2 (2 mL) and subjected to column
chromatography. Elution with neat CH2Cl2 gave a yellow fraction.
Removal of solvent in vacuo, followed by crystallization from CH2-
Cl2-petroleum ether, yielded yellow microcrystals of [N(PPh3)2]-
[2,2,2-(CO)3-closo-2,1-FeCB8H9] (4; 0.14 g).
Structure Determinations. Diffraction-quality crystals of com-
pounds 3-5 were obtained by slow diffusion of petroleum ether
into CH2Cl2 solutions at -30 °C; those of 6 and 9 were grown by
slow cooling of saturated hexane solutions to -30 °C, while those
of 7 and 8 were grown similarly from pentane solutions at the same
temperature. Experimental data for compounds 3-9 are reported
in Table 4. Diffraction data were acquired at 110(2) K using a
Bruker-Nonius X8 Apex area-detector diffractometer (graphite-
monochromated Mo KR radiation, λ ) 0.71073 Å). Several sets
of data frames were collected at different θ values for various initial
values of φ and ω, each frame covering a 0.5 increment in φ or ω.
The data frames were integrated using SAINT;28 the substantial
redundancy in data allowed empirical absorption corrections
(SADABS)28 to be applied on the basis of multiple measurements
of equivalent reflections.
Synthesis of [N(PPh3)2][6,6,6-(CO)3-closo-6,1-FeCB8H9]. The
compounds [Fe3(CO)12] (0.40 g, 0.79 mmol) and [NBun ][closo-
4
4-CB8H9] (ca. 0.18 g, 0.5 mmol) were heated to reflux in THF (10
mL) for 18 h. The mixture was then cooled to room temperature,
and [N(PPh3)2]Cl (0.29 g, 0.5 mmol) was added. Solvent was
removed in vacuo, and the residue was dissolved in CH2Cl2 (2 mL)
and transferred to the top of a chromatography column. Elution
with CH2Cl2 gave a pale yellow fraction. Removal of solvent in
vacuo followed by crystallization from CH2Cl2-petroleum ether
yielded yellow microcrystals of [N(PPh3)2][6,6,6-(CO)3-closo-6,1-
FeCB8H9] (5; 0.16 g).
The structures were solved (SHELXS-97) via conventional direct
methods andsfor all but 3swere refined (SHELXL-97) by full-
matrix least-squares on all F2 data using SHELXTL.28,29 All non-
hydrogen atoms were assigned anisotropic displacement parameters.
The locations of the cage carbon atoms were verified by examina-
tion of the appropriate internuclear distances and the magnitudes
of their isotropic thermal displacement parameters. All of the
hydrogen atoms in organic functions, plus terminal cluster H atoms
in the structure of 9, were set riding on their parent atoms in
calculated positions; all other cluster H atoms were located in
difference maps and allowed positional refinementswith the
exception of the B-H-Fe bridging hydrogens in 9, which could
only be positionally refined subject to restraints (DFIX card in
SHELXL with B-H 1.20(5) Å and Fe-H 1.60(5) Å). All hydrogen
atoms were assigned fixed isotropic thermal parameters calculated
as Uiso(H) ) 1.2 × Uiso(parent), or Uiso(H) ) 1.5 × Uiso(parent)
for methyl hydrogens.
Synthesis of [4,9-{Fe(CO)4}-4-(µ-H)-9,9,9-(CO)3-arachno-9,6-
FeCB8H11]. Compound 3 (0.23 g, 0.25 mmol) was dissolved in
CH2Cl2 (10 mL), CF3SO3H (0.25 mL) was added, and the mixture
was stirred at room temperature for 30 min. After filtration through
Celite, the filtrate was evaporated in vacuo. The residue was
dissolved in CH2Cl2 (2 mL) and transferred to the top of a
chromatography column. Elution with CH2Cl2-petroleum ether (1:
1) gave a yellow fraction from which removal of solvent in vacuo
followed by crystallization from CH2Cl2-petroleum ether afforded
yellow microcrystals of [4,9-{Fe(CO)4}-4-(µ-H)-9,9,9-(CO)3-
arachno-9,6-FeCB8H11] (6; 0.080 g).
(24) Ellis, D. D.; Franken, A.; Jelliss, P. A.; Stone, F. G. A.; Yu, P.-Y.
Organometallics 2000, 19, 1993.
(25) Ellis, D. D.; Franken, A.; Jelliss, P. A.; Kautz, J. A.; Stone, F. G. A.;
Yu, P.-Y. J. Chem. Soc., Dalton Trans. 2000, 2509.
Crystals of 3 contained three formula units per asymmetric
fraction, with the three independent units differing primarily in the
(26) Franken, A.; Du, S.; Jelliss, P. A.; Kautz, J. A.; Stone, F. G. A.
Organometallics 2001, 20, 1597.
(27) Jardine, F. H.; Rule, J.; Vohra, G. A. J. Chem. Soc. A 1970, 238.
(28) APEX 2, version 1.0; Bruker AXS: Madison, WI, 2003-2004.
(29) SHELXTL, version 6.12; Bruker AXS: Madison, WI, 2001.
2676 Inorganic Chemistry, Vol. 45, No. 6, 2006
Franken, Andreas
