Endohedral metallocenophanes of rhodium and cobalt

Article abstract of DOI:10.1002/ejic.200400851

The synthesis of seven endohedral metallocenophanes of rhodium (7b, 8b) and cobalt (1d-h) with a cyclopentadienyl unit as one of the π-systems and a cyclobutadiene or cyclopentadienone unit as the second π-system is described, including the synthesis of the unsubstituted parent compound of the [CpCo(cbd)]-derived endohedral phanes, [3.3]-η⁵-(1,1′,3, 3′)-cyclopentadienyl-η⁴-(cyclobutadienophane)cobalt(I) (1h). This compound could be obtained by deprotection of the corresponding trimethylsilyl-substituted endohedral phane 1g. The X-ray structures of 7b, 1e, 1g and 1h could be obtained. This paper compares their structural properties to the complexes reported in previous short communications.

Full text of DOI:10.1002/ejic.200400851

FULL PAPER
Endohedral Metallocenophanes of Rhodium and Cobalt
Carsten Schaefer,[a] Gerald Scholz,[a] Rolf Gleiter,*[a] Thomas Oeser,[a] and
Frank Rominger[a]
Dedicated to Professor Paul von Ragué Schleyer on the occasion of his 75th birthday
Keywords: Cage compounds / Sandwich complexes / Alkynes / Rhodium / Cobalt
The synthesis of seven endohedral metallocenophanes of
rhodium (7b, 8b) and cobalt (1dϪh) with a cyclopentadienyl
unit as one of the π-systems and a cyclobutadiene or cyclo-
pentadienone unit as the second π-system is described, in-
cluding the synthesis of the unsubstituted parent compound
of the [CpCo(cbd)]-derived endohedral phanes, [3.3]-η5-
(1,1Ј,3,3Ј)-cyclopentadienyl–η4-(cyclobutadienophane)co-
balt(I) (1h). This compound could be obtained by deprotec-
tion of the corresponding trimethylsilyl-substituted endohed-
ral phane 1g. The X-ray structures of 7b, 1e, 1g and 1h could
be obtained. This paper compares their structural properties
to the complexes reported in previous short communications.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
is able to stabilize low oxidation states of the incorporated
metals. This has been demonstrated by complexing GaI and
GeII in [2.2.2]paracyclophane.[6] In the literature there are
reports of two protocols for the synthesis of endohedral
metallocenophanes:
Either by reacting metal atoms or metal ions directly
with the appropriate cyclophanes (path I in Scheme 1),[6,7]
or by building the tethers on a metallocene in a stepwise
fashion (path II).[8] Recently, we developed a third path (III)
by utilizing substituted half-sandwich complexes which are
able to form the second π-system by an intramolecular me-
tal mediated cyclization of alkyne units (Scheme 1).[9]
Introduction
In [n.n]phanes[1Ϫ4] the cyclic conjugated π-systems which
are held in place by at least two bridges, such as hydro-
carbon chains, offer a variety of bonding modes for metal
centres. The cage structures of these phanes exhibit an in-
side and an outside face leading to two binding modes for
a metal atom or metal fragment to the π-systems: inside the
cage (endohedral, A) or outside the cage (exohedral, B) as
shown in Figure 1.[5]
Figure 1. Endohedral (A) and exohedral (B) bonding modes of
metallocenophanes.
Scheme 1. Protocols I–III for the synthesis of endohedral metall-
In comparison to the numerous examples of the exohed-
ral metallocenophanes reports of endohedral phanes are
much rarer because of their limited accessibility. However,
ocenophanes.
Using this third synthetic pathway we were able to syn-
they deserve special interest because the hydrocarbon cage thesize the cobalt and rhodium complexes 1aϪh, 2c, 3a–b,
4a–b, 5a, and 6a (Figure 2), of which 1a, 1b, 1e, 1g, 1h, 5a,
and 6a were investigated by X-ray diffraction.[9,10]
In this paper we report the synthesis of two endohedral
rhodium phanes 7b and 8b (Figure 3), four endohedral co-
[a] Organisch-Chemisches Institut, Universität Heidelberg,
INF 270, 69120 Heidelberg, Germany
Fax: +49-6221-544205
E-mail: Rolf.Gleiter@urz.uni-heidelberg.de
1274
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200400851
Eur. J. Inorg. Chem. 2005, 1274–1281

Endohedral Metallocenophanes of Rhodium and Cobalt
FULL PAPER
Scheme 2. Synthesis of ω-haloalkynes 11a–d [n = 3, R = tBu (a); n
= 4, R = tBu (b); n = 5, R = tBu (c); n = 3, R = SiMe3 (d)] from
ω-hydroxy alcohols 9a–c [n = 3, R = tBu (a); n = 4, R = tBu (b);
n = 5, R = tBu (c)].
The disubstituted cyclopentadiene derivatives that we
used as ligands for the half-sandwich complexes were syn-
thesized by a two step procedure (Scheme 3).[9] In the first
step the first alkyne substituent was introduced by treat-
ment of 3-ethoxycyclopent-2-ene-1-one (12) with a Grig-
nard reagent of an ω-chloroalkyne 11. Acidic workup of the
reaction mixture yielded the respective 3-alkynylcyclopent-
2-enones 13. The second alkyne substituent was introduced
in a similar reaction and again acidic workup led to the
desired disubstituted cyclopentadienes. The resulting cyclo-
pentadiene derivatives were deprotonated with n-butyllith-
ium in THF shortly before their complexation with metal
dicarbonyl fragments.
Figure 2. Endohedral metallocenophanes 1a–h, 2c, 3a–b, 4a–b, 5a,
and 6a synthesized by route III [m = n = 3, R = tBu (a); m = n =
4, R = tBu (b); m = n = 5, R = tBu (c); m = 3, n = 4, R = tBu (d);
m = 3, n = 5, R = tBu (e); m = 4, n = 5, R = tBu (f); m = n = 3,
R = SiMe3 (g); m = n = 3, R = H (h)].
balt phanes 1d–g (Figure 2) and of the unsubstituted parent
compound 1h of phane 1a.
Scheme 3. Two step synthesis of 1,3-difunctionalized cyclopen-
tadienyllithium salts [14b]– (n = m = 4, R = tBu) and [14dϪg]– [n
= 3, m = 4, R = tBu (d); n = 3, m = 5, R = tBu (e); n = 4, m = 5,
R = tBu (f); m = n = 3, R = SiMe3 (g)]. Reagents: (a) ClMgϪ
(CH2)mCϵCR in THF, then HCl (aq); (b) ClMg–(CH2)nCϵR in
THF, then HCl (aq); (c) n-butyllithium in THF.
Figure 3. Isomeric rhodium phanes 7b and 8b (m = n = 4, R =
tBu).
In the case of the rhodium complexes, the lithium salt
[14b]– was treated with the dicarbonyl(chloro)rhodium di-
mer in THF to yield the dicarbonyl rhodium complex 15b
(Scheme 4) as an orange oil in 77% yield.
Results and Discussion
The thermolytic reaction of the dicarbonyl rhodium
complex 15b in refluxing cyclooctane yielded two isomeric
Synthesis
The synthesis of the ω-haloalkynes 11a–d necessary as endohedral products, 7b and 8b (Figure 3). While 7b was
building blocks for the tethers in the endohedral phanes formed in an acceptable yield of 16%, 8b was only pro-
was achieved by the substitution of tosylated ω-chloro duced in minor quantities (0.5% yield). We were able to
alcohols 10a–c by lithiated tert-butylacetylene or (trimeth- grow single crystals of 7b which were suitable for X-ray dif-
ylsilyl)acetylene, respectively (Scheme 2).
fraction analysis. This allowed us to confirm the structure
Eur. J. Inorg. Chem. 2005, 1274–1281
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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C. Schaefer, G. Scholz, R. Gleiter, T. Oeser, F. Rominger
FULL PAPER
Structural Investigations
Crystals suitable for X-ray crystallographic studies could
be obtained for the complexes 7b, 1e, 1g and 1h. In Fig-
ure 4, the molecular structures of these endohedral phanes
are shown.
Scheme 4. Synthesized dicarbonyl metal complexes 15b (n = m =
4, R = tBu) and 16dϪg [n = 3, m = 4, R = tBu (d); n = 3, m = 5,
R = tBu (e); n = 4, m = 5, R = tBu (f); m = n = 3, R = SiMe3 (g)].
of 7b and also to assign the structure of 8b. For the isomeric
endohedral products six isomers are possible, of which four
are Cs and two C1 symmetric. The NMR spectroscopic data
for 7b and 8b prove the C1 symmetry of both isolated com-
plexes 7b and 8b. As we were able to confirm the structure
of 7b by X-ray analysis the structure of 8b could also be
assigned unambiguously.
Until now only endohedral cobalt phanes bearing alkyl
chains of the same length (m = n) had been synthesized.[9,10]
To investigate the amount of distortion resulting from two
different alkyl chains, the endohedral cobalt phanes 1d (m
= 3, n = 4, R = tBu), 1e (m = 3, n = 5, R = tBu), 1f (m =
4, n = 5, R = tBu) were envisaged. To obtain the dicarbonyl
cobalt complexes 16d–f we reacted the deprotonated cyclo-
pentadiene derivatives [14d–f]– with [Co2(CO)8]/I2. The
thermolytic reaction of these half-sandwich complexes in
refluxing cyclooctane resulted in the formation of the en-
dohedral complexes 1d–f in 5% (1d), 30% (1e) and 15%
(1f) yield.
For the synthesis of the parent compound 1h of the re-
cently published endohedral [3.3]phane 1a we made use of
TMS as protecting groups on the cyclobutadiene unit
(Scheme 5).[11] The twofold TMS substituted phane 1g was
obtained in 35% yield analogously to 1a by refluxing the
dicarbonyl cobalt complex 16g in cyclooctane. The removal
of the TMS groups was achieved in 74% yield by stirring a
solution of 1g with Me4NF at 80 °C.
Figure 4. ORTEP plots (50% ellipsoid probability) of the molecular
structures of 7b, 1g (left), 1e and 1h (right).
Including the previously described molecular struc-
tures,[9,10] a total number of eight crystallographically
studied endohedral phanes synthesized with our protocol
are available and can now be compared. Selected structural
properties of these complexes are listed in Table 1.
Table 1. Structural properties of endohedral metallocenophanes 1a,
1b, 1g, 1h, 5a, 6a and 7b.[a]
Interplanar angle
Angle
β [°]
(η5-Cp)ϪM MϪ(η4-ligand)
α [°]
distance [Å]
distance [Å]
1a[9]
1b[9]
1e
6.6
4.0
13.6
6.8/7.2
9.9
4.3
22.2
5.1
174.2
178.3
166.9
173.6/173.1
170.8
175.6
1.604
1.670
1.677
1.609/1.604
1.590
1.777
1.645
1.692
1.678
1.645/1.650
1.631
1.742
1 g[b]
1h
5a[10]
6a[10]
7b
170.9
174.8
1.806
1.857
1.751
1.791
[a] For the calculation of angles and centroids, all five C atoms of
the Cp rings were used, but only the four coordinated C atoms of
the η4-ligands (cyclopentadienone or cyclobutadiene). [b] The two
different values refer to two independent molecules in the unit cell.
The larger atomic radius of rhodium results in larger dis-
tances between the metal centre and the coordinated η5-
Cp ligand as well as the η4-coordinated unit. While these
distances for the rhodium complexes range from 1.78–
1.86 Å [(η5-Cp)···M distance] and 1.74–1.79 Å [M···(η4-li-
gand) distance], the cobalt complexes show values of 1.59–
1.68 Å [(η5-Cp)···M distance] and 1.63–1.69 Å [M···(η4-li-
gand) distance]. Within these limits the distances vary ac-
Scheme 5. Synthesis of unsubstituted phane 1h by deprotection.
1276
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 1274–1281

Endohedral Metallocenophanes of Rhodium and Cobalt
FULL PAPER
cording to the lengths of the alkyl chains and to the substi- the cyclopentadienone ligand was generated. A comparison
tution pattern. First, the structural features of the rhodium of five endohedral (η5-Cp)Co(η4-Cbd) metallocenophanes
complexes shall be compared. Generally there exist six pos- revealed the anticipated shortest metal–ligand distances for
sible isomers for endohedral [n.n]phanes with a Cp and a the [3.3]cyclophane, whereas the other bridges led to
cyclopentadienone unit, namely two C1- and four Cs-sym- metalϪligand distances close to the unbridged species. The
metric. Of these six isomers three are represented by the relatively short metalϪligand distances for the [3.3]bridged
complexes 5a (C1), 6a (Cs) and 7b (C1). Because of the species are also encountered in the case of the rhodium spe-
shorter alkyl bridges the two [3.3]phanes 5a and 6a are cies 5a and 6a.
more strained than the [4.4]phane 7b, which has the largest
distances between the rhodium centre and the π-ligands.
The two [3.3]phanes also differ in the strain of the carbon
Experimental Section
cage. The substitution pattern of the π-ligands in the Cs- General Remarks: All melting points are uncorrected. Elemental
analyses were carried out by the Mikroanalytisches Laboratorium
der Universität Heidelberg. UV/Vis absorption data were recorded
with a Hewlett Packard HP 8452A Diode Array-spectrometer. IR
spectra were recorded with a Bruker Vector 22 FT-IR spectrometer.
The NMR spectra were measured with a Bruker WH 300 or Av-
ance 500 spectrometer (1H NMR at 300 or 500 MHz and 13C NMR
at 75 or 125 MHz) using the solvent as internal standard (δ). Stan-
dard symbols for signal multiplicities are used; p = pseudo. FAB
and FD mass spectra refer to data from a Jeol JMS-700 instrument.
All reactions were carried out in dried glassware under argon using
dried and oxygen-free solvents.
symmetric phane 6a allows the molecule to reduce the
strain by increasing the interplanar angle α (22.2°), which
is the largest of all the investigated complexes (Figure 5).
The C1-symmetric [3.3]phane 5a does not have that much
flexibility to reduce strain because of the substitution
pattern of the alkyl chains and, therefore, shows a small
interplanar angle (α = 4.3°) as well as the shortest
rhodium···π-ligand distances.
X-ray Crystallographic Study: Data were collected with a Bruker
Smart CCD-diffractometer at 200 K (7b and 1e) and a Bruker
Smart Apex-diffractometer at 295 K (1g and 1h). Relevant crystal
and data collection parameters are given in Table 2. The structures
were solved by direct methods and refined against F2 with a full-
matrix least-square algorithm by using SHELXTL[13] software. In
all cases an absorption correction was applied by using SAD-
ABS,[14] based on the Laue symmetry of the reciprocal space.
Figure 5. Illustration of the interplanar angle α and angle β.
In the row of the cobalt complexes the shortest bonding
lengths between the cobalt centre and the π-ligands are
found in the unsubstituted [3.3]phane 1h [1.590 Å (η5-
Cp)ϪM distance, 1.631 Å MϪ(η4-ligand) distance]. These
distances are shorter than those reported for the unbridged
species [(η5-Cp)ϪM 1.660 Å and MϪ(η4-ligand)
1.681 Å].[12] Addition of sterically demanding substituents
on the cbd-unit increases these distances, with TMS groups
[1.609/1.604 Å (η5-Cp)ϪM distance, 1.645/1.650 Å MϪ(η4-
ligand) distance] having practically the same effect as tBu
groups [1.604 Å (η5-Cp)ϪM distance, 1.645 Å MϪ(η4-li-
gand) distance]. The metal-ligand distances for 1b and 1e
are rather close to the parent system.[12] All the symmetri-
cally bridged endohedral cobalt phanes (n = m) 1a, 1b, 1g
and 1h show nearly parallel π-systems, with the interplanar
angles α ranging from 4.0 to 9.9°. In the unsymmetrically
bridged 1e the distortion leads to an enlarged interplanar
angle α (13.6°) and to a remarkably small angle β (166.9°),
the smallest in all investigated phanes.
CCDC-249232 (for 1e), -249234 (for 1g), -249233 (for 1h), and
-249231 (for 7b) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
General Procedure for the Preparation of ω-Chloroalkynes 11aϪd:
A dry 100-mL flask was charged with the respective 4-toluenesulfo-
nate, dry THF and tert-butylammonium bromide (TBAB) and the
mixture was cooled to 0 °C. Alkynyllithium (prepared by the ad-
dition of n-butyllithium to 1-alkyne in THF) was then added with
a cannula. The mixture was stirred at 0 °C (1 h) then allowed to
reach room temp. overnight. The solvent was removed, water was
added to the residue and the solution was extracted with diethyl
ether. The organic layer was washed with brine, dried (MgSO4),
filtered and the solvent was evaporated under reduced pressure.
The products were purified by distillation.
1-Chloro-6,6-dimethylhept-4-yne (11a): Reaction mixture: 3-chlo-
ropropyl-1-tosylate (10a) (2.49 g, 10 mmol) and TBAB (3.22 g,
10 mmol) in THF (20 mL), 3,3-dimethylbut-1-yne (0.82 g,
10 mmol) and n-butyllithium (3.6 mL, 2.8 m) in THF (20 mL).
Yield 1.19 g (75%). Colorless liquid, b.p. 49 °C (2 mbar). 1H NMR
(300 MHz, CDCl3): δ = 1.18 (s, 9 H, CH3), 1.90 (pquint, 3J =
Conclusions
3
6.6 Hz, 2 H, CH2), 2.31 (t, J = 6.8 Hz, 2 H, CH2), 3.63 (t, 3J =
6.5 Hz, 2 H, CH2) ppm. 13C NMR (75 MHz, CDCl3): δ = 16.9
Our method of synthesizing metallocenophanes in situ
by generating one ligand out of tethered precursors pro-
vided us with endohedral complexes of cobalt and rhodium.
The yields were low (5%) to moderate (35%). In the case
of the cobalt complexes, the generation of a cyclobutadiene
or a cyclopentadienone ring is dependent on the reaction
(CH2), 28.0 (C), 32.0 (CH3), 32.6 (CH2), 44.5 (CH2), 77.0 (C), 90.8
(C) ppm. IR (film) ν = 2968, 2929, 2867, 1477, 1456 cm–1. HRMS
˜
(positive EI) calcd. for C9H15Cl ([M]+), 160.0833; found, 160.0875
(+4.2 mmu).
1-Chloro-7,7-dimethyloct-5-yne (11b): Reaction mixture: 4-chlo-
temperature. From the dicarbonyl rhodium complexes only robutyl-1-tosylate (10b) (2.63 g, 10 mmol) and TBAB (3.22 g,
Eur. J. Inorg. Chem. 2005, 1274–1281
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C. Schaefer, G. Scholz, R. Gleiter, T. Oeser, F. Rominger
FULL PAPER
Table 2. Crystal data and structural refinement for 7b, 1e, 1g and 1h.
7b
1e
1g
1h
Empirical formula
Formula mass
C26H37ORh
468.47
C25H37Co
396.48
C21H33CoSi2
400.58
C15H17Co
256.22
Wavelength [Å]
Crystal system
Space group
0.71073
tetragonal
I41/a
0.71073
monoclinic
P21/n
0.71073
monoclinic
P21/n
0.71073
orthorhombic
Pbca
Temp. [K]
Z
200
16
200
4
295
8
295
8
a
b
c
α
14.3272(3)
14.3272(3)
42.901(1)
90
9.1546(2)
16.4597(3)
14.1320(3)
90
8.925(2)
25.475(7)
19.307(5)
90
7.5187(8)
16.561(2)
18.839(2)
90
β
γ
90
90
8806.2(4)
1.413
0.789
0.95/0.88
polyhedron
0.17×0.15×0.06
1.5–24.7
–16 Յ h Յ 16
–16 Յ k Յ 16
–50 Յ l Յ 50
37141
3763 (0.108)
2466 [I Ͼ 2σ(I)]
3763/10/278
1.02
91.063(1)
90
2129.07(8)
1.24
94.448(6)
90
4377(2)
1.22
0.89
0.76/0.97
plate
0.33×0.22×0.03
1.92–28.36
–11 Յ h Յ 11
–34 Յ k Յ 11
–22 Յ l Յ 25
21679
10521 (0.173)
5773 [I Ͼ 2σ(I)]
10521/0/445
1.05
90
90
2345.7(4)
1.45
1.43
0.56/0.96
needle
0.45×0.11×0.03
2.16–28.35
–9 Յ h Յ 10
–10 Յ k Յ 22
–25 Յ l Յ 25
16177
2906 (0.046)
2443 [I Ͼ 2σ(I)]
2906/0/213
1.26
V [Å3]
Dcalcd. [g/cm3]
Abs. coeff. μ [mm–1]
Max./min. transmission
Crystal shape
Crystal size [mm3]
θ range for data collection [°]
Index ranges
0.81
0.93/0.59
polyhedron
0.48×0.42×0.10
1.9–27.5
–11 Յ h Յ 11
–21 Յ k Յ 21
–18 Յ l Յ 18
21428
4883 (0.035)
3835 [I Ͼ 2σ(I)]
4883/0/241
1.06
Reflections collected
Independent reflections [R(int.)]
Observed reflections
Data/restraints/parameters
Goodness-of-fit on F2
R(F)
0.054
0.116
2.70 and –1.39
0.078
0.209
1.54 and –0.70
0.088
0.247
0.94 and –1.95
0.055
0.111
0.34 and –0.46
RW(F2)
(Δρ)max., (Δρ)min. [e·Å–3]
3
3
10 mmol) in THF (20 mL), 3,3-dimethylbut-1-yne (0.82 g,
10 mmol) and n-butyllithium (3.6 mL, 2.8 m) in THF (20 mL).
= 6.6 Hz, 2 H, CH2), 2.40 (t, J = 6.9 Hz, 2 H, CH2), 3.63 (t, J =
6.4 Hz, 2 H, CH2) ppm. 13C NMR (125 MHz, CDCl3): δ = 0.2
Yield 1.21 g (70%). Colorless liquid, b.p. 54 °C (1 mbar). 1H NMR (CH3), 17.4 (CH2), 31.5 (CH2), 43.7 (CH2), 85.8 (C), 105.3 (C)
(500 MHz, CDCl3): δ = 1.18 (s, 9 H, CH3), 1.62 (pquint, 3J =
ppm. IR (film) ν = 2960, 2176, 1431, 1361 cm–1. HRMS (positive
˜
7.2 Hz, 2 H, CH2), 1.87 (pquint, J = 7.1 Hz, 2 H, CH2), 2.18 (t, EI) calcd. for C8H15ClSi ([M]+), 174.0632; found, 174.0567
3
3
3J = 7.0 Hz, 2 H, CH2), 3.56 (t, J = 6.6 Hz, 2 H, CH2) ppm. 13C
NMR (125 MHz, CDCl3): δ = 18.7 (CH2), 26.9 (CH2), 28.0 (C),
32.0 (CH3), 32.3 (CH2), 45.4 (CH2), 78.2 (C), 90.4 (C) ppm. IR
(–6.5 mmu).
General Procedure for the Synthesis of Cyclopent-2-enones 13a–c:
In a dry 50-mL flask a Grignard reagent was prepared from chlo-
roalkyne and magnesium in dry THF. The resulting solution was
cooled to 0 °C and 3-ethoxycyclopent-2-enone, dissolved in dry
THF, was added dropwise. The reaction mixture was stirred at 0 °C
(film) ν = 2968, 2866, 1477, 1779, 1476, 1362 cm–1. HRMS (posi-
˜
tive EI) calcd. for C10H17Cl ([M]+), 172.1019; found, 172.1023
(+0.4 mmu).
1-Chloro-8,8-dimethylnon-6-yne (11c): Reaction mixture: 5-chlo- (1 h) and then warmed to room temp. overnight. The reaction mix-
ropentyl-1-tosylate (10c) (2.77 g, 10 mmol) and TBAB (3.22 g,
10 mmol) in THF (20 mL), 3,3-dimethylbut-1-yne (0.82 g,
10 mmol) and n-butyllithium (3.6 mL, 2.8 m) in THF (20 mL).
ture was poured into ice, and the solution was acidified with 5%
hydrochloric acid to pH 5. After extraction with diethyl ether the
organic layer was washed with brine, dried (MgSO4), filtered and
Yield 1.31 g (70%). Colorless liquid, b.p. 63 °C (2 mbar). 1H NMR the solvent was evaporated under reduced pressure. The products
(300 MHz, CDCl3): δ = 1.17 (s, 9 H, CH3), 1.45–1.55 (m, 4 H,
CH2), 1.72–1.85 (m, 2 H, CH2), 2.13 (t, 3J = 6.5 Hz, 2 H, CH2),
3.51 (t, CH2, 3J = 6.7 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 19.2 (CH2), 26.7 (CH2), 28.0 (C), 29.0 (CH2), 32.1 (CH3), 32.8
were purified by flash column chromatography (silica gel, petro-
leum ether/diethyl ether, 3:1).
3-(6,6-Dimethylhept-4-ynyl)cyclopent-2-enone (13a): Reaction mix-
ture: 1-chloro-6,6-dimethylhept-4-yne (11a) (6.03 g, 38 mmol) and
magnesium (0.92 g, 38 mmol) in THF (10 mL), 3-ethoxycyclopent-
2-enone (3.0 g, 23.8 mmol) in THF (10 mL). Yield 3.11 g (64%).
Colorless oil. 1H NMR (300 MHz, CDCl3): δ = 1.17 (s, 9 H, CH3),
(CH ), 45.6 (CH ), 78.6 (C), 90.1 (C) ppm. IR (film) ν = 2968,
˜
2
2
2864, 1476, 1361 cm–1. HRMS (positive EI) calcd. for C11H19Cl
([M]+), 186.1175; found, 186.1171 (–0.4 mmu).
3
3
5-Chloropent-1-ynyltrimethylsilane (11d): Reaction mixture: 3-chlo-
ropropyl-1-tosylate (10a) (2.49 g, 10 mmol) and TBAB (3.22 g,
10 mmol) in THF (20 mL), (trimethylsilyl)acetylene (0.98 g,
10 mmol) and n-butyllithium (3.6 mL, 2.8 m) in THF (20 mL).
Yield 1.36 g (78%). Colorless liquid, b.p. 80 °C (28 mbar). 1H
1.68–1.76 (pquint, J = 7.1 Hz, 2 H, CH2), 2.19 (t, J = 6.9 Hz, 2
H, CH2), 2.38 (m, 2 H, CH2), 2.47–2.52 (m, 2 H, CH2), 5.94 (s, 1
H, CH) ppm. 13C NMR (125 MHz, CDCl3): δ = 18.3 (CH2), 26.4
(CH2), 27.3 (C), 31.3 (CH3), 31.5 (CH2), 32.3 (CH2), 35.2 (CH2),
77.3 (C), 90.1 (C), 129.6 (CH), 182.3 (C), 210.0 (C) ppm. IR (film)
3
NMR (500 MHz, CDCl3): δ = 0.14 (s, 9 H, CH3), 1.95 (pquint, J
ν = 2967, 2866, 1710, 1675, 1616, 1437, 1361 cm–1. HRMS (positive
˜
1278
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 1274–1281

Endohedral Metallocenophanes of Rhodium and Cobalt
EI) calcd. for C14H20O ([M]+), 204.1514; found, 204.1511 (–0.3 and magnesium (0.70 g, 29 mmol) in THF (6 mL), 3-(7,7-dimeth-
FULL PAPER
mmu). C14H20O (204.31): calcd. C 82.30, H 9.87, found C 82.02,
H 10.32.
yloct-5-ynyl)cyclopent-2-enone (13b) (3.21 g, 14.7 mmol) in THF
(10 mL). Yield 2.44 g (47%).
3-(7,7-Dimethyloct-5-ynyl)cyclopent-2-enone (13b): Reaction mix-
ture: 1-chloro-7,7-dimethyloct-5-yne (11b) (6.56 g, 38 mmol) and
magnesium (0.92 g, 38 mmol) in THF (10 mL), 3-ethoxycyclopent-
2-enone (3.0 g, 23.8 mmol) in THF (10 mL). Yield 2.65 g (51%).
Colorless oil. 1H NMR (300 MHz, CDCl3): δ = 1.14 (s, 9 H, CH3),
1.44–1.49 (m, 2 H, CH2), 1.62–1.68 (m, 2 H, CH2), 2.13 (t, 3J =
6.9 Hz, 2 H, CH2), 2.34–2.41 (m, 4 H, CH2), 2.53–2.55 (m, 2 H,
CH2), 5.91–5.92 (m, 1 H, CH) ppm. 13C NMR (75 MHz, CDCl3):
δ = 19.0 (CH2), 26.6 (CH2), 27.9 (C), 29.2 (CH2), 32.0 (CH3), 32.1
(CH2), 33.6 (CH2), 35.9 (CH2), 78.2 (C), 90.2 (C), 130.2 (CH),
1,3-Bis[5-(trimethylsilyl)pent-4-ynyl]cyclopentadi-ene (14g): (5-
Chloropent-1-ynyl)trimethylsilane (11d) (5.07 g, 29 mmol) and
magnesium (0.70 g, 29 mmol) in THF (6 mL), 3-[5-(trimethylsilyl)
pent-4-ynyl]cyclopent-2-enone (13g) (3.24 g, 14.7 mmol) in THF
(10 mL). Yield 2.37 g (64%).
Dicarbonyl-η5-[1,3-bis(7,7-dimethyloct-5-ynyl)cyclopentadienyl]rho-
dium(I) (15b): n-Butyllithium (2.6 mL, 1.6 m in hexane, 2.68 mmol)
was added to a solution of cyclopentadiene 14b (1.12 g, 3.30 mmol)
in 10 mL of THF at –40 °C. After warming up to room tempera-
ture the solution was added to a solution of dicarbonyl(chloro)
rhodium(i) dimer (0.50 g, 0.83 mmol) in 100 mL of THF and
stirred for 24 h. The solvents were removed under vacuum and the
products purified by flash column chromatography on silica gel
using pentanes/diethyl ether (20:1) as eluent. Yield 636 mg (77%).
Orange oil. 1H NMR (500 MHz, CDCl3): δ = 1.17 (s, 18 H, CH3),
1.50 (m, 4 H, CH2), 1.58 (m, 4 H, CH2), 2.13 (m, 4 H, CH2), 2.25
(m, 4 H, CH2), 5.25 (ps, 2 H, CH), 5.38 (ps, 1 H, CH) ppm. 13C
NMR (125 MHz, CDCl3): δ = 18.5 (CH2), 27.4 (C), 27.9 (CH2),
183.4 (C), 210.7 (C) ppm. IR (film) ν = 2966, 2930, 2864, 1710,
˜
1675, 1616, 1437, 1361 cm–1. UV/Vis (CH2Cl2): λmax. (log ε) = 276
(2.56), 310 (1.82) nm. HRMS (positive EI) calcd. for C15H22O
([M]+), 218.1671; found, 218.1672 (+0.1 mmu). C15H22O (218.33):
calcd. C 82.52, H 10.16; found C 82.11, H 10.36.
3-[5-(Trimethylsilyl)pent-4-ynyl]cyclopent-2-enone (13g): Reaction
mixture: (5-chloropent-1-ynyl)trimethylsilane (11d) (6.64 g,
38 mmol) and magnesium (0.92 g, 38 mmol) in THF (10 mL), 3-
ethoxycyclopent-2-enone (3.0 g, 23.8 mmol) in THF (10 mL). Yield
4.14 g (79%). Colorless oil. 1H NMR (500 MHz, CDCl3): δ = 0.14
28.9 (CH2), 31.4 (CH2), 31.5 (CH3), 78.0 (C), 86.0 (CH, JRh,C
3.8 Hz), 89.1 (CH, JRh,C = 3.8 Hz), 89.5 (C), 110.6 (C, JRh,C
=
=
3
3
(s, 9 H, CH3), 1.79 (pquint, J = 7.3 Hz, 2 H, CH2), 2.28 (t, J =
3.8 Hz), 192.7 (CO, JRh,C = 83.8 Hz) ppm. IR (film) ν = 2967,
˜
3
2862, 2034, 1969, 1476, 1456, 1361 cm–1. UV/Vis (CH2Cl2): λmax
.
6.9 Hz, 2 H, CH2), 2.39–2.41 (m, 2 H, CH2), 2.51 (t, J = 7.7 Hz,
2 H, CH2), 2.57–2.59 (m, 2 H, CH2), 5.94–5.96 (m, 1 H, CH) ppm.
13C NMR (125 MHz, CDCl3): δ = 0.2 (CH3), 19.6 (CH2), 26.0
(CH2), 31.7 (CH2), 32.5 (CH2), 35.4 (CH2), 85.9 (C), 106.0 (C),
129.9 (CH), 181.9 (C), 210.0 (C) ppm. HRMS (positive EI) calcd.
for C13H20OSi ([M]+), 220.1283; found, 220.1283 ( 0.0 mmu). IR
(log ε)= 240 (4.18), 296 (3.62) nm. MS (positive FD): m/z = 468
([M – CO]+).
General Procedure for the Synthesis of Dicarbonylcobalt Complexes
16d–g: A dry flask was charged with [Co2(CO)8] and dry THF, I2
was added and the green mixture stirred at room temp. for 1 h. The
green solution was cooled to 0 °C and a solution of cyclopentadien-
yllithium (prepared by the addition of n-butyllithium to a solution
of cyclopentadiene in dry THF at –40 °C) was added. The brown
mixture was stirred at 0 °C (1 h), then allowed to warm to room
temp. overnight. The solvent was evaporated under reduced pres-
sure and the product was purified by flash column chromatography
[alox III (neutral), petroleum ether].
(film) ν = 2957, 2174, 1710, 1675, 1616, 1438, 1409, 1249, 1183,
˜
842, 760 cm–1. C13H20OSi (220.38): calcd. C 70.85, H 9.15; found
C 70.91, H 9.32.
General Procedure for the Synthesis of Cyclopentadienes 14b and
14d–g: In a dry 50-mL flask a Grignard reagent was prepared from
chloroalkyne and magnesium in dry THF. The resulting solution
was cooled to 0 °C, cyclopent-2-enone dissolved in dry THF, was
added. The mixture was stirred at 0 °C (1 h) and then allowed to
reach room temp. overnight. The reaction mixture was poured into
ice, the solution was acidified with 5% hydrochloric acid to pH 5
and extracted with diethyl ether. The organic layer was washed with
brine, dried (MgSO4), filtered and the solvent was evaporated un-
der reduced pressure. The product was purified by flash column
chromatography [alox III (neutral), petroleum ether] and used di-
rectly for the complexation after the removal of solvent.
Dicarbonyl-η5-[1-(6,6-dimethylhept-4-ynyl)-3-(7,7-dimethyloct-5-
ynyl)cyclopentadienyl]cobalt(I) (16d): Reaction mixture: [Co2(CO)8]
(402 mg, 1.2 mmol) and I2 (299 mg, 1.2 mmol) in THF (25 mL), 1-
(6,6-dimethylhept-4-ynyl)-3-(7,7-dimethyloct-5-ynyl)cyclopentadi-
ene (14d) (0.9 g, 2.8 mmol) and n-butyllithium (2.4 mL, 1.6 m in
hexane) in THF (5 mL). Yield 285 mg (55%). Orange oil. 1H NMR
(300 MHz, C6D6): δ = 1.32 (s, 9 H, CH3), 1.34 (s, 9 H, CH3), 1.50–
1.64 (m, 6 H, CH2), 2.10–2.56 (m, 8 H, CH2), 4.57 (s, 2 H, CH),
4.70 (s, 1 H, CH) ppm. 13C NMR (75 MHz, C6D6): δ = 18.7 (CH2),
18.9 (CH2), 27.4 (CH2), 27.7 (C), 28.0 (CH2), 29.2 (CH2), 30.1
(CH2), 30.3 (CH2), 31.7 (CH3), 78.1 (C), 78.5 (C), 83.5 (CH), 83.6
(CH), 85.6 (CH), 89.5 (C), 90.0 (C), 105.4 (C), 106.1 (C) ppm. IR
1,3-Bis(7,7-dimethyloct-5-ynyl)cyclopentadiene (14b): Reaction mix-
ture: 1-chloro-7,7-dimethyloct-5-yne (11b) (5.01 g, 29 mmol) and
magnesium (0.70 g, 29 mmol) in THF (6 mL), 3-(7,7-dimethyloct-
5-ynyl)cyclopent-2-enone (13b) (3.21 g, 14.7 mmol) in THF
(10 mL). Yield 3.19 g (64%).
(film) ν = 2964, 2862, 2044, 1952, 1475, 1453, 1360 cm–1. UV/Vis
˜
1-(6,6-Dimethylhept-4-ynyl)-3-(7,7-dimethyloct-5-ynyl)cyclopentadi-
ene (14d): Reaction mixture: 1-chloro-7,7-dimethyloct-5-yne (11b)
(5.01 g, 29 mmol) and magnesium (0.70 g, 29 mmol) in THF
(CH2Cl2): λmax. (log ε)= 252 (6.71), 336 (2.76), 360 (2.49).
Dicarbonyl-η5-[1-(6,6-dimethylhept-4-ynyl)-3-(8,8-dimethylnon-6-
ynyl)cyclopentadienyl]cobalt(I) (16e): Reaction mixture: [Co2(CO)8]
(6 mL),
3-(7,7-dimethylhept-4-ynyl)cyclopent-2-enone
(13a)
(388 mg, 1.1 mmol) and I2 (288 mg, 1.1 mmol) in THF (25 mL), 1-
(6,6-dimethylhept-4-ynyl)-3-(8,8-dimethylnon-6-ynyl)cyclopentadi-
ene (14e) (1.0 g, 3.0 mmol) and n-butyllithium (2.6 mL, 1.6 m in
hexane) in THF (5 mL).Yield 130 mg (25%). Orange oil. 1H NMR
(500 MHz, C6D6): δ = 1.20 (s, 9 H, CH3), 1.25 (s, 9 H, CH3), 1.35–
1.53 (m, 6 H, CH2), 2.03–2.40 (m, 10 H, CH2), 4.49 (s, 1 H, CH),
4.50 (s, 1 H, CH), 4.61 (s, 1 H, CH) ppm. 13C NMR (125 MHz,
C6D6): δ = 18.7 (CH2), 19.0 (CH2), 27.4 (CH2), 27.7 (C), 28.3
(CH2), 28.8 (CH2), 29.2 (CH2), 30.2 (CH2), 30.3 (C), 30.6 (CH2),
(3.00 g, 14.7 mmol) in THF (10 mL). Yield 0.91 g (19%).
1-(6,6-Dimethylhept-4-ynyl)-3-(8,8-dimethylnon-6-ynyl)cyclopenta-
diene (14e): Reaction mixture: 1-chloro-8,8-dimethylnon-6-yne
(11c) (5.41 g, 29 mmol) and magnesium (0.70 g, 29 mmol) in THF
(6 mL), 3-(7,7-dimethylhept-4-ynyl)cyclopent-2-enone (13a)
(3.00 g, 14.7 mmol) in THF (10 mL). Yield 3.53 g (71%).
1-(7,7-Dimethyloct-5-ynyl)-3-(8,8-dimethylnon-6-ynyl)cyclopentadi-
ene (14f): 1-Chloro-8,8-dimethylnon-5-yne (11c) (5.41 g, 29 mmol)
Eur. J. Inorg. Chem. 2005, 1274–1281
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1279

C. Schaefer, G. Scholz, R. Gleiter, T. Oeser, F. Rominger
FULL PAPER
31.5 (CH3), 31.6 (CH3), 78.1 (C), 78.8 (C), 83.5 (CH), 83.6 (CH), calcd. for C26H38ORh ([M]+), 469.1978; found, 469.1939 (–3.9
85.6 (CH), 89.3 (C), 90.0 (C), 105.3 (C), 106.2 (C) ppm. IR (film) mmu).
ν = 2964, 2920, 2850, 2015, 1955, 1474, 1455 cm–1. UV/Vis
(CH2Cl2): λmax. (log ε) = 250 (3.77), 306 (3.00), 330 (2.85) nm.
˜
General Procedure for the Synthesis of Endohedral Cobalt Com-
plexes 1d–g: A dry 250-mL flask was charged with the dicarbon-
Dicarbonyl-η5-[1-(7,7-dimethyloct-5-ynyl)-3-(8,8-dimethylnon-6-
ynyl)cyclopentadienyl]cobalt(I) (16f): Reaction mixture: [Co2(CO)8]
ylcobalt complex and cyclooctane. The solution was refluxed
(12 h). The solvent was evaporated under reduced pressure and the
products were purified by column chromatography (alox III).
[3.4]-η5-(1,1Ј,3,3Ј)-Cyclopentadienyl-η4-[2,4-bis(tert-butyl)cyclobuta-
dienophane]cobalt(I) (1d): Reaction mixture: complex 16d (140 mg,
0.40 mmol) in cyclooctane (80 mL). Yield 20 mg (5%). Yellow so-
lid, m.p. 110 °C. 1H NMR (500 MHz, C6D6): δ = 1.20 (s, 18 H,
CH3), 1.54–1.81 (br., 8 H, CH2), 2.03–2.12 (br., 4 H, CH2), 2.24–
2.27 (m, 1 H, CH2), 2.53–2.61 (m, 1 H, CH2), 4.56 (s, 1 H, CH),
4.79 (s, 1 H, CH), 5.00 (s, 1 H, CH) ppm. 13C NMR (125 MHz,
C6D6): δ = 23.5 (CH2), 24.3 (CH2), 29.3 (CH2), 29.6 (CH2), 29.7
(CH2), 31.2 (CH2), 31.6 (CH3), 32.4 (C), 32.7 (C), 33.0 (CH3), 39.0
(CH2), 66.1 (C), 80.9 (CH), 81.1 (C), 81.3 (CH), 81.8 (CH), 92.7
(458 mg, 1.3 mmol) and I2 (340 mg, 1.3 mmol) in THF (28 mL),
1-(7,7-dimethyloct-5-ynyl)-3-(8,8-dimethylnon-6-ynyl)cyclopenta-
diene (14f) (1.1 g, 3.2 mmol) and n-butyllithium (1.8 mL, 2.5 m in
hexane) in THF (6 mL).Yield 250 mg (40%). Orange oil. 1H NMR
(300 MHz, C6D6): δ = 0.80–0.87 (m, 4 H, CH2), 1.24 (s, 18 H,
CH3), 1.30–1.50 (br., 6 H, CH2), 1.86–1.91 (m, 4 H, CH2), 2.01–
2.09 (m, 4 H, CH2), 4.48 (s, 2 H, CH), 4.60 (s, 1 H, CH) ppm. 13C
NMR (75 MHz, C6D6): δ = 18.9 (CH2), 19.1 (CH2), 27.7 (C), 28.0
(CH2), 28.4 (CH2), 28.9 (CH2), 29.2 (CH2), 29.3 (CH2), 30.1 (C),
30.3 (CH2), 30.6 (CH2), 31.6 (CH3), 31.7 (CH3), 78.6 (C), 78.8 (C),
83.4 (CH), 83.5 (CH), 85.6 (CH), 89.3 (C), 89.6 (C), 106.0 (C),
106.2 (C) ppm. IR (film) ν = 2967, 2930, 2860, 2016, 1955, 1475,
˜
(C), 93.2 (C), 95.3 (C), 95.5 (C) ppm. IR (KBr) ν = 3079, 2953,
˜
1455, 1388 cm–1. UV/Vis (CH2Cl2): λmax. (log ε) = 246 (4.27), 294
2910, 2849, 1622, 1478, 1460, 1442, 1391 cm–1. UV/Vis (CH2Cl2):
λmax. (log ε) = 268 (4.16), 302 (3.24), 342 (2.80) nm. HRMS
(positive EI) calcd. for C24H35Co ([M]+), 383.2071; found, 383.2057
(–1.4 mmu). C24H35Co (382.47): calcd. C 75.37, H 9.22; found C
75.47, H 8.99.
(2.87) nm.
Dicarbonyl-η5-[1,3-bis(5-trimethylsilylpent-4-ynyl)cyclopentadienyl]-
cobalt(I) (16g): Reaction mixture: [Co2(CO)8] (1.2 g, 3.5 mmol) and
I2 (896 mg, 3.5 mmol) in THF (75 mL), 1,3-bis[5-(trimethylsilyl)
pent-4-ynyl]cyclopentadiene (14g) (2.7 g, 7.8 mmol) and n-butyl-
lithium (6.3 mL, 1.6 m in hexane) in THF (15 mL). Yield 696 mg
[3.5]-η5-(1,1Ј,3,3Ј)-Cyclopentadienyl-η4-[2,4-bis(tert-butyl)cyclobuta-
dienophane]cobalt(I) (1e): Reaction mixture: complex 16e (130 mg,
1
0.29 mmol) in cyclooctane (50 mL). Yield 34 mg (30%). Yellow so-
lid, m.p. 140 °C. 1H NMR (300 MHz, C6D6): δ = 1.14 (s, 9 H,
CH3), 1.16 (s, 9 H, CH3), 1.37–1.74 (m, 8 H, CH2), 1.82–1.88 (m,
4 H, CH2), 2.19–2.23 (m, 1 H, CH2), 2.39–2.43 (m, 1 H, CH2),
2.59–2.62 (m, 2 H, CH2), 4.58 (s, 1 H, CH), 4.70 (s, 1 H, CH), 4.78
(s, 1 H, CH) ppm. 13C NMR (125 MHz, C6D6): δ = 22.9 (CH2),
23.1 (CH2), 24.0 (CH2), 24.3 (CH2), 25.0 (CH2), 26.1 (CH2), 31.4
(CH3), 32.1 (CH3), 32.4 (C), 32.6 (C), 37.7 (CH2), 66.4 (C), 73.4
(C), 78.8 (CH), 81.0 (CH), 81.3 (CH), 90.7 (C), 92.1 (C) 93.5 (C),
(57%). Orange oil. H NMR (300 MHz, C6D6): δ = 0.17 (s, 18 H,
CH3), 1.37–1.46 (m, 4 H, CH2), 1.94–2.07 (m, 8 H, CH2), 4.40 (s,
2 H, CH), 4.48 (s, 1 H, CH) ppm. 13C NMR (75 MHz, C6D6): δ =
0.4 (CH3), 19.8 (CH2), 27.3 (CH2), 29.7 (CH2), 83.5 (CH), 85.4
(CH), 85.5 (C), 105.1 (C), 106.9 (C) ppm. IR (film) ν = 2858, 2174,
˜
2046, 2016, 1955, 1427, 1326 cm–1. UV/Vis (CH2Cl2): λmax. (log ε)
= 250 (4.03), 330 (3.21) nm.
Synthesis of Endohedral Rhodium Complexes 7b and 8b: A dry 250-
mL flask was charged with cyclopentadienyl(dicarbonyl)rhodium
(15b, 636 mg, 1.28 mmol) and 120 mL cyclooctane. The solution
was refluxed (72 h). The solvent was evaporated under reduced
pressure and the products were purified by column chromatog-
raphy [alox III (neutral)]. After eluting the column with petroleum
ether in the beginning, dichloromethane was used to elute first
complex 7b and then complex 8b as yellow bands.
94.2 (C) ppm. IR (KBr) ν = 2955, 2919, 2855, 1478, 1455,
˜
1372 cm–1. UV/Vis (CH2Cl2): λmax. (log ε) = 270 (4.49), 300 (3.54),
374 (3.20) nm. HRMS (positive EI) calcd. for C25H37Co ([M]+),
396.2227; found, 396.2238 (+1.1 mmu). C25H37Co (396.49): calcd.
C 75.37, H 9.41; found C 75.37, H 9.28.
[4.5]-η5-(1,1Ј,3,3Ј)-Cyclopentadienyl-η4-[2,4-bis(tert-butyl)cyclobuta-
dienophane]cobalt(I) (1f): Reaction mixture: complex 16f (165 mg,
Complex 7b: Yield 95 mg (16%). Yellow solid. 1H NMR (500 MHz,
CDCl3): δ = 1.49 (s, 9 H, CH3), 1.51 (s, 9 H, CH3), 1.56 (m, 2 H,
CH2), 1.73 (m, 2 H, CH2), 1.79 (m, 2 H, CH2), 1.90 (m, 2 H, CH2),
2.19 (m, 2 H, CH2), 2.22 (m, 2 H, CH2), 2.58 (m, 2 H, CH2), 2.71
(m, 2 H, CH2), 5.15 (ps, 1 H, CH), 5.28 (ps, 1 H, CH), 5.35 (ps, 1
H, CH) ppm. 13C NMR (75 MHz, CDCl3): δ = 26.0 (CH2), 27.0
(CH2), 27.2 (CH2), 29.1 (CH2), 29.7 (CH2), 30.0 (CH2), 30.8 (CH2),
31.6 (CH3), 32.1 (CH2), 33.4 (C), 33.9 (C), 34.5 (CH3), 83.2 (CH,
0.35 mmol) in cyclooctane (60 mL). Yield 22 mg (15%). Yellow so-
lid, m.p. 151 °C. 1H NMR (300 MHz, C6D6): δ = 1.22 (s, 9 H,
CH3), 1.23 (s, 9 H, CH3), 1.25–1.56 (m, 4 H, CH2), 1.44–1.61 (m,
4 H, CH2), 1.88–1.89 (m, 1 H, CH2), 1.89–1.95 (m, 2 H, CH2),
2.09–2.14 (m, 1 H, CH2), 2.21–2.28 (m, 1 H, CH2), 2.30–2.34 (m,
1 H, CH2), 2.41–2.49 (m, 1 H, CH2), 2.53–2.55 (m, 2 H, CH2),
2.65–2.71 (m, 1 H, CH2), 4.65 (s, 1 H, CH), 4.76 (s, 1 H, CH), 4.84
(s, 1 H, CH) ppm. 13C NMR (125 MHz, C6D6): δ = 23.4 (CH2),
23.7 (CH2), 23.9 (CH2), 25.3 (CH2), 25.4 (CH2), 27.3 (CH2), 27.5
(CH2), 28.9 (CH2), 31.6 (CH2), 31.8 (CH3), 31.9 (CH3) 32.6 (C),
69.7 (C), 74.1 (C), 77.8 (CH), 79.5 (CH), 79.8 (CH), 87.7 (C), 89.6
JRh,C = 5.6 Hz), 84.0 (CH, JRh,C = 6.5 Hz), 85.7 (C, JRh,C
8.8 Hz), 86.2 (CH, JRh,C = 6.8 Hz), 93.5 (C, JRh,C = 9.3 Hz), 93.9
(C, JRh,C = 10.1 Hz), 106.1 (C, JRh,C = 5.5 Hz), 106.4 (C, JRh,C
=
=
6.3 Hz), 111.1 (C, JRh,C = 11.4 Hz), 163.2 (CO) ppm. MS (positive
(C), 95.4 (C), 95.6 (C) ppm. IR (KBr) ν = 2957, 2921, 2857, 2026,
˜
FAB): m/z = 468 [M]+. IR (KBr) ν = 2922, 2857, 2232, 1733, 1598,
1628, 1479, 1458 cm–1. UV/Vis (CH2Cl2): λmax. (log ε) = 278 (4.34),
322 (3.18), 372 (2.98) nm. HRMS (positive EI) calcd. for C26H39Co
([M]+), 410.2384; found, 410.2336 (–4.8 mmu).
˜
1485, 1448, 1388 cm–1. UV/Vis (CH2Cl2): λmax. (log ε) = 266 (5.05),
348 (4.42) nm. HRMS (positive FAB) calcd. for C26H37ORhNa
([M + Na]+), 491.1797; 491.1804 found, (+0.7 mmu).
[3.3]-η5-(1,1Ј,3,3Ј)-Cyclopentadienyl-η4-[2,4-bis(trimethylsilyl)cyclo-
butadienophane]cobalt(I) (1g): Reaction mixture: complex 16g
Complex 8b: Yield 3 mg (0.5%). Yellow oil. 1H NMR (500 MHz,
CDCl3): δ = 1.41 (s, 9 H, CH3), 1.58 (s, 9 H, CH3), 1.91–2.62 (m, (665 mg, 360 mmol) in cyclooctane (360 mL). Yield 207 mg (35%).
1
16 H, CH2), 5.33 (ps, 1 H, CH), 5.38 (ps, 1 H, CH), 5.50 (ps, 1 H, Yellow solid, m.p. 55 °C. H NMR (500 MHz, C6D6): δ = 0.14 (s,
CH) ppm. MS (positive FD): m/z = 468 [M]+. IR (film) ν = 2925, 9 H, CH3), 0.24 (s, 9 H, CH3), 1.41–1.56 (br., 4 H, CH2), 1.73–1.85
˜
2856, 1562, 1446, 1362, 1261, 1029 cm–1. HRMS (positive FAB)
(br., 6 H, CH2), 2.04–2.14 (m, 2 H, CH2), 4.55 (s, 1 H, CH), 4.56
1280
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Eur. J. Inorg. Chem. 2005, 1274–1281

Endohedral Metallocenophanes of Rhodium and Cobalt
FULL PAPER
(s, 1 H, CH), 5.13 (s, 1 H, CH) ppm. 13C NMR (125 MHz, C6D6):
δ = 1.7 (CH3), 1.9 (CH3), 26.0 (CH2), 26.9 (CH2), 40.8 (CH2), 77.3
(C), 79.5 (C), 80.1 (CH), 84.1 (C), 84.3 (CH), 95.0 (C) ppm. IR
[1] R. Gleiter, H. Hopf (Eds.), Modern Cyclophane Chemistry,
Wiley-VCH, Weinheim, 2004.
[2] F. Vögtle, Cyclophane Chemistry: Synthesis Structures and Re-
actions, Wiley, Chichester, 1993.
(KBr) ν = 2936, 2912, 2849, 1627, 1545, 1421, 1324 cm–1. UV/Vis
˜
(CH2Cl2): λmax. (log ε)= 266 (4.01), 310 (3.31), 398 (2.71) nm. [3] P. M. Keehn, S. M. Rosenfeld (Eds.), Cyclophanes, Academic
HRMS (positive EI) calcd. for C21H33CoSi2 ([M]+), 400.1453;
found, 400.1477 (+2.4 mmu).
Press, New York, 1983.
[4] F. Diederich, Cyclophanes, The Royal Society of Chemistry,
London, 1991.
[5] a) J. Schulz, F. Vögtle, Top. Curr. Chem. 1994, 172, 41–86; b)
R. Gleiter, B. J. Rausch, R. J. Schaller, in: Modern Cyclophane
Chemistry (Eds.: R. Gleiter, H. Hopf), Wiley-VCH, Weinheim,
2004, 159–188.
[6] H. Schmidbaur, Angew. Chem. 1985, 97, 893–904; Angew.
Chem. Int. Ed. Engl. 1985, 24, 893–904.
[7] a) C. Elschenbroich, R. Möckel, U. Zenneck, Angew. Chem.
1978, 90, 560–561; Angew. Chem. Int. Ed. Engl. 1978, 17, 531–
532; b) A. R. Koray, M. L. Ziegler, N. E. Blank, M. W. Haenel,
Tetrahedron Lett. 1979, 26, 2465–2466.
[8] M. Hisatome, Rev. Heteroatom Chem. 1992, 6, 142–176.
[9] G. Scholz, R. Gleiter, F. Rominger, Angew. Chem. 2001, 113,
2559–2562; Angew. Chem. Int. Ed. 2001, 40, 2477–2479.
[10] G. Scholz, C. Schaefer, F. Rominger, R. Gleiter, Org. Lett.
2002, 4, 2889–2892.
[11] R. I. Duclos, K. P. C. Vollhardt, L. S. Yee, J. Organomet. Chem.
1979, 174, 109–114.
[12] P. E. Riley, R. E. Davis, J. Organomet. Chem. 1976, 113, 157–
166.
[3.3]-η5-(1,1Ј,3,3Ј)-Cyclopentadienyl-η4-(cyclobutadienophane)co-
balt(I) (1h): A dry 25-mL flask was charged with complex 1g
(126 mg, 0.32 mmol), tetramethylammonium fluoride tetrahydrate
(408 mg, 2.47 mmol) and DMSO (10 mL). The solution was stirred
at 80 °C (15 h). Then the mixture was extracted with petroleum
ether (8×). The organic layer was washed with water and dried
(MgSO4). The solvent was removed under reduced pressure and
the product was purified by column chromatography [alox III (neu-
tral)]. Yield 61 mg (74%). Yellow solid, m.p. 77 °C. 1H NMR
(300 MHz, C6D6): δ = 1.09–1.25 (m, 4 H, CH2), 1.53 (pt, 2J =
12.7 Hz, 2 H, CH2), 1.77–1.93 (m, 4 H, CH2), 2.17 (pd, 2J =
4
14.4 Hz, 2 H, CH2), 3.68 (pd, J = 8.0 Hz, 1 H, CH), 4.45–4.47 (d,
4J = 8.0 Hz, 1 H, CH), 4.53 (s, 2 H, CH), 4.66 (s, 1 H, CH) ppm.
13C NMR (75 MHz, C6D6): δ = 25.4 (CH2), 25.9 (CH2), 37.7
(CH2), 66.1 (CH), 67.9 (CH), 72.2 (C), 78.7 (CH), 83.2 (CH), 94.9
(C) ppm. IR (KBr) ν = 3072, 2910, 2867, 2831, 1627, 1428,
˜
1407 cm–1. UV/Vis (CH2Cl2): λmax. (log ε) = 254 (4.31), 284 (3.30),
362 (3.01) nm. HRMS (positive EI) calcd. for C15H17Co ([M]+),
265.0662; found, 265.0649 (–1.3 mmu).
[13] SHELXTL G. M. Sheldrick, Bruker Analytical X-ray-Divi-
sion, Madison, Wisconsin, 2001.
[14] G. M. Sheldrick, 1996, unpublished work based on the method
described in: R. H. Blessing, Acta Crystallogr. Sect. A 1995,
S1–S33.
Acknowledgments
Received: October 11, 2004
We are grateful to the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, and the BASF Aktiengesell-
schaft, Ludwigshafen, Germany, for financial support.
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