Alkyne substitution on cobaltocenium triflates

Article abstract of DOI:10.1002/ejic.200800088

Cobaltocenium triflates consisting of a CpCo-capped η⁵-1- trifluoromethylsulfonyloxy-2,3,4,5-tetrapropylcyclopentadienyl ring were substituted at the Cp ring by a trialkylsilylethynyl group to yield the R-CpCo capped tetra-n-propylcyclopentadienone with R = C₂SiMe₃ (11a) and R = C₂SiEt₃ (11b). The parent system with R = C₂H (11c) was generated by hydrolyzing the SiR₃ groups of 11a and 11b. The trialkylsilyl-1,3-butadiyne derivatives with alkyl = CH ₃ (11d) and alkyl = C₂H₅ (11e) were derived from 11c by using a Cadiot-Chodkiewicz coupling with bromo(triethylsilyl) acetylene. Removal of the SiEt₃ protecting group led to 11f. The alkynes 11c and 11f could be dimerized to 13a and 13b by a Hay coupling. These results were confirmed by X-ray diffraction studies on the starting materials 7, 8, and 12 as well as the derivatives 11c, 11f, and 13a. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200800088

FULL PAPER
DOI: 10.1002/ejic.200800088
Alkyne Substitution on Cobaltocenium Triflates
Mareile von der Grün,[a] Rolf Gleiter,*[a] and Frank Rominger[a]
Keywords: Alkynes / Conjugation / SNЈ substitution / Cyclopentadienone / Rodlike molecules / Cobalt
Cobaltocenium triflates consisting of a CpCo-capped η5-
1-trifluoromethylsulfonyloxy-2,3,4,5-tetrapropylcyclopenta-
dienyl ring were substituted at the Cp ring by a trialkylsilyl-
ethynyl group to yield the R–CpCo capped tetra-n-propyl-
cyclopentadienone with R = C2SiMe3 (11a) and R = C2SiEt3
(11b). The parent system with R = C2H (11c) was generated
by hydrolyzing the SiR3 groups of 11a and 11b. The trialkyl-
silyl-1,3-butadiyne derivatives with alkyl = CH3 (11d) and
alkyl = C2H5 (11e) were derived from 11c by using a Cadiot–
Chodkiewicz coupling with bromo(triethylsilyl)acetylene.
Removal of the SiEt3 protecting group led to 11f. The alkynes
11c and 11f could be dimerized to 13a and 13b by a Hay
coupling. These results were confirmed by X-ray diffraction
studies on the starting materials 7, 8, and 12 as well as the
derivatives 11c, 11f, and 13a.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
connected through the ligands (see 1–3)[2–4] or they can be
bonded directly to the alkyne bridges (see 4–6).[5–14] In both
types bulky termini are connected by a carbon rod.
Recently we found a simple way of carrying out substitu-
In material science, model systems with two redox-active
centers are often connected with conjugated bridges such
as polyalkenes and polyalkynes. Since the first investi-
gations on diferrocenylalkynes[1,2] the interest in dinuclear
complexes has increased considerably.[1–12] The most well- tion reactions at the η5-cyclopentadienyl ring of co-
known species are diferrocenylalkynes (1)[1,2] and related baltocenium triflates by an SNЈ reaction.[15] In these species
species 2–6[1–6] (Scheme 1). The metal centers can be a nucleophile attacks the Cp ring of the cobaltocenium ion
Scheme 1. Model systems of two redox-active centers connected by alkyne units.
whereas the leaving group is situated at the other five-mem-
[a] Organisch-Chemisches Institut der Universität Heidelberg,
Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
bered ring. This reaction is shown in Scheme 2.
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Alkyne Substitution on Cobaltocenium Triflates
plexes. In this paper we report on the synthesis and the
properties of 11a–11f, 12 as well as 13a and 13b (Schemes 3
and 4).
Results and Discussion
To obtain the alkynes 11a–11f we followed the protocol
shown in Scheme 2. The lithium salt of the monoprotected
alkyne was treated with 8. When we used trimethyl-
silylacetylene to prepare 11a from 8 the yield was only 16%.
To find out if other substituents at the cyclopentadienone
ring of 8 can increase the yield we prepared the cobaltocen-
ium triflate 15 from the readily available tetraphenyl-cyclo-
pentadienone complex 14[16] (Scheme 4) by treating 14 with
trifluoromethanesulfonic anhydride at –30 °C. The resulting
cobaltocenium salt 15 was treated with the in situ prepared
lithium salt of trimethylsilyl acetylene (TMSA). The re-
sulting tetraphenylcyclopentadienone complex 12 was ob-
tained in 19% yield, indicating that the substituents at the
cyclopentadienone ring were not responsible for the low
yields. Better yields were obtained when we used triethylsi-
lylacetylene instead of trimethylsilylacetylene. Starting from
8 we synthesized 11b in 56% yield. For 11a as well as for
11b we were able to cleave the protecting groups by treating
them with a 5  aqueous solution of NaOH at room tem-
perature. The yield of 11c was Ͼ95%.
Scheme 2. Generation of 8 and SNЈ substitution to yield 10.
(a) (CF3SO2)2O/CH2Cl2/–50 °C); (b) RLi/THF/–30 °C.
The starting point is the readily available CpCo-capped
cyclopentadienone complex 7. Treatment of 7 with trifluo-
romethanesulfonic anhydride afforded the cobaltocenium
triflate 8 in good yields. When the latter was treated with
alkyl- and aryllithium compounds a substitution at the Cp
ring occurred to give 10 in yields between 60 and 80%.[15]
This reaction should also provide a simple means to prepare
alkyne-substituted CpCo-capped cyclopentadienone com-
To synthesize the 1,3-butadiyne substituted derivatives
11d and 11e we first tried to react 8 with the lithium salt of
trimethylsilyl-1,3-butadiyne. However, the yield was rather
low (16%). In a second experiment we followed a sugges-
tion in the literature[17] and tried to generate the anion of
trimethylsilyl-1,3-butadiyne in situ from 1,4-bis(trimethyl-
silyl)-1,3-butadiyne (16) (Scheme 5) and methyllithium. The
addition of a THF solution of 8 to the mixture resulted in
only 11% of 11d as a red oil. After these failures we used a
stepwise approach. The key step in this protocol was a
Cadiot–Chodkiewicz coupling reaction[18] between 11c and
bromo(triethylsilyl)acetylene in the presence of CuI and
ethylamine. This protocol afforded 11e in 80% yield as a
red oil (Scheme 6). The parent system 11f was generated by
the treatment of 11e with (nBu)4NF in THF as red crystals.
Scheme 3. Target molecules.
Scheme 4. (a) (CF3SO2)2O/CH2Cl2/–50 °C; (b) Me3Si–CϵC–H/
nBuLi/THF/–30 °C.
Scheme 5. (a) MeLi/LiBr/–50 °C/THF.
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M. von der Grün, R. Gleiter, F. Rominger
FULL PAPER
Hay protocol[19] proved to be very efficient. The products
13a and 13b could be isolated in yields of 80 and 90%,
respectively.
For 7, 8, 11c, 11f, 12, and 13a we were able to isolate
single crystals, which allowed us to carry out X-ray diffrac-
tion studies. In Figure 1 we show the molecular structures
of 11c, 11f, and 13a.
The distance between the cobalt center and the plane of
the cyclopentadienyl unit is 1.67 Å for all three structures
and is close to the values reported for other CpCo–cyclo-
pentadienone complexes.[20] The same holds for the distance
between the metal and the plane of the four alkyl-substi-
tuted carbon atoms of the cyclopentadienone unit, which
was found to be 1.62 Å for 11c and 1.63 Å for 11f and 13a.
The distances between the Cp rings and the adjacent sp
centers vary between 1.43 Å (11c, 11f) and 1.42 Å (13a).
The bond lengths of the alkyne units are 1.18 Å (11c),
1.20 Å, 1.38 Å, 1.18 Å (11f), and 1.19 Å, 1.39 Å, 1.19 Å
(13a). The angles at the triple bonds deviate slightly from
180°. These values and angles are very similar to those of
other alkyne chains between metallorganic units.[21]
Scheme 6. (a) nBuLi/THF/–40 °C; (b) CuI/–15 °C; (c) EtNH2/
–25 °C; (d) Br–CϵC–SiEt3/–25 °C, (e) 1  nBu4NF/THF.
The alkynes 11c and 11f were ideal precursors to try an
oxidative coupling reaction between the alkyne units. We
chose the protocol suggested by Hay[19] using CuCl in the
presence of pyridine (Scheme 7). For 11c as well as 11f the
Experimental Section
General Remarks: All melting points are uncorrected. The NMR
spectra were measured with a Bruker Avance 300 spectrometer (1H
NMR at 300 MHz and 13C NMR at 75 MHz) and a Bruker Avance
500 spectrometer (1H NMR at 500 MHz and 13C NMR at
125 MHz) using the solvent as internal standard (δ). The mass
spectra refer to data from a JEOL JMS-700 instrument. IR spectra
were recorded with a Bruker Vector 22 FT-IR spectrometer. All
reactions were carried out in dried glassware under argon using
dried and oxygen-free solvents.
Scheme 7. (a) CuCl/O2/pyridine.
[(2,3,4,5-η)-2,3,4,5-Tetrapropylcyclopenta-2,4-dien-1-one](η5-cyclo-
pentadienyl)cobalt(I) (7): A solution of CpCo(CO)2 (6.1 g,
34 mmol) in decalin (150 mL) was heated at 190 °C. 4-Octyne
(3.3 g, 30 mmol) dissolved in decalin (150 mL) was then added over
8 h. When the addition was completed the heating was continued
for an additional 5 d. The reaction mixture was cooled to room
temperature and then filtered through neutral alumina, activity III.
The solvent decalin and unreacted CpCo(CO)2 were extracted with
petroleum ether as the eluent. The cyclopentadienone complex was
chromatographed with CH2Cl2/MeOH (50:1) as a broad orange
band. After removal of the solvent the crude product was purified
again by column chromatography on neutral alumina, activity III,
with CH2Cl2/MeOH (20:1) to yield complex 7 (3.0 g, 54%) as an
orange-red solid; m.p. 113 °C. 1H NMR (500 MHz, CDCl3): δ =
0.97 (t, 6 H, CH3), 0.99 (t, 6 H, CH3), 1.41–1.45 (m, 6 H, CH2),
1.67 –1.70 (m, 2 H, CH2), 1.88–1.93 (m, 2 H, CH2), 2.25–2.49 (m,
6 H, CH2), 4.60 (s, 5 H, CpCH) ppm. 13C NMR (125 MHz, CDCl3):
δ = 15.5 (CH3), 15.6 (CH3), 23.4 (CH2), 25.2 (CH2), 28.5 (CH2),
29.1 (CH2), 82.6 (Ccpd), 83.0 (CpCH), 92.9 (Ccp d), 158.7
(C=O) ppm. IR (KBr): ν = 3082 (m), 2960 (vs), 2935 (s), 2871 (s),
˜
1575 (vs), 1466 (s), 1377 (m) cm–1. UV/Vis (CH2Cl2): λmax (log ε)
= 288 (4.45), 362 (3.57), 420 (3.32) nm. HRMS (FAB): calcd.
373.1942; found 373.1916. C22H33CoO (372.43): calcd. C 70.95, H
8.93; found C 70.84, H 8.95.
(η5-1-Trifluoromethylsulfonyloxy-2,3,4,5-tetrapropylcyclopentadi-
enyl)(η5-cyclopentadienyl)cobalt(III) Trifluoromethansulfonate (8):
The cyclopentadienone complex 7 (2.5 g, 6.7 mmol), dissolved in
Figure 1. Molecular structures of 11c (top), 11f, and 13a (bottom).
The hydrogen atoms have been omitted for the sake of clarity.
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Alkyne Substitution on Cobaltocenium Triflates
dichloromethane (20 mL), was added to a cooled (–50 °C) solution
of trifluoromethanesulfonic anhydride (2.8 g, 10.1 mmol) in dry
dichloromethane (70 mL) over a period of 15 min. The mixture was
warmed and stirred for 12 h at room temperature. After evapora-
tion of the solvent, ether (100 mL) was added. The precipitate was
filtered off and recrystallized from CH2Cl2/Et2O. Complex 8
(3.59 g, 82%) was obtained as a yellow solid; m.p. 161 °C. 1H NMR
(300 MHz, CDCl3): δ = 1.03 (t, 6 H, CH3), 1.07 (t, 6 H, CH3),
1.41–1.56 (m, 8 H, CH2), 2.44–2.72 (m, 8 H, CH2), 5.59 (s, 5 H,
CpCH) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.4 (CH3), 14.7
[(2,3,4,5-η)-2,3,4,5-Tetrapropylcyclopenta-2,4-dien-1-one](η5-tri-
ethylsilylethynylcyclopentadienyl)cobalt(I) (11b): Complex 11b
(437 mg, 56%) was obtained as a dark-red oil. 1H NMR (500 MHz,
CD2Cl2): δ = 0.87 (q, 6 H, SiCH2), 1.15 (t, 9 H, SiCH2CH3), 1.20
(t, 6 H, CH3), 1.24 (t, 6 H, CH3), 1.56–1.70 (m, 6 H, CH2), 1.78–
1.87 (m, 2 H, CH2), 2.08–2.14 (m, 2 H, CH2), 2.45–2.52 (m, 2 H,
CH2), 2.56–2.64 (m, 4 H, CH2), 4.85–4.86 (m, 2 H, CpCH), 4.92–
4.93 (m, 2 H, CpCH) ppm. 13C NMR (125 MHz, CD2Cl2): δ = 4.7
(SiCH2), 7.7 (SiCH2CH3), 14.9 (CH3), 15.0 (CH3), 22.9 (CH2), 24.6
(CH2), 27.5 (CH2), 27.6 (CH2), 79.1 (Csp), 82.3 (C), 84.5 (CpCH),
(CH3), 24.0 (CH2), 25.1 (CH2), 26.1 (CH2), 27.4 (CH2), 88.2 85.2 (CpCH), 92.3 (C), 92.9 (C), 100.2 (C), 158.9 (C=O) ppm. IR
(CpCH), 95.6 (Ccpd), 98.9 (Ccpd), 118.1 (COTf) ppm. IR (KBr): ν = (KBr): ν = 2958 (vs), 2934 (vs), 2873 (vs), 2153 (s), 1571 (vs), 1457
˜
˜
3102 (w), 2969 (m), 2880 (w), 1631 (w), 1466 (m), 1421 (s), 1269
(s), 1237 (m) cm–1. UV/Vis (CH2Cl2): λmax (log ε) = 272 (4.00), 304
(s), 1224 (s), 1141 (s) cm–1. UV/Vis (CH2Cl2): λmax (log ε) = 288 (4.24), 372 (3.52), 416 (3.14) nm. HRMS (FAB): calcd. 511.2806;
(4.55) nm. HRMS (FAB): calcd. 505.1434; found 505.1455.
C24H33CoF6O6S2 (654.56): calcd. C 44.04, H 5.08; found C 44.21,
H 5.26.
found 511.2823. C30H47CoOSi (510.72): calcd. C 70.55, H 9.28;
found C 70.49, H 9.30.
[(2,3,4,5-η)-2,3,4,5-Tetrapropylcyclopenta-2,4-dien-1-one](η5-ethyn-
ylcyclopentadienyl)cobalt(I) (11c): NaOH (0.95 mmol, 5  solution)
was added to a solution of 11b (439 mg, 0.86 mmol) in methanol
(10 mL). After 15 min water and ether were added, the layers were
separated, and the aqueous layer was washed three times with
ether. The combined organic layers were dried with MgSO4, the
solvent was removed, and the crude mixture was purified by col-
umn chromatography on silica gel with CH2Cl2/MeOH (20:1).
Complex 11c (337 mg, 99%) was obtained as a dark-red solid; m.p.
115 °C. 1H NMR (500 MHz, CD2Cl2): δ = 0.97 (t, 6 H, CH3), 1.01
(t, 6 H, CH3), 1.40–1.49 (m, 6 H, CH2), 1.63–1.66 (m, 2 H, CH2),
1.85–1.91 (m, 2 H, CH2), 2.24–2.30 (m, 2 H, CH2), 2.35–2.43 (m,
4 H, CH2), 3.03 (s, 1 H, Cϵ CH), 4.67–4.68 (m, 2 H, CpCH), 4.70–
4.71 (m, 2 H, CpCH) ppm. 13C NMR (125 MHz, CD2Cl2): δ = 14.9
(CH3), 14.9 (CH3), 22.8 (CH2), 24.5 (CH2), 27.6 (CH2), 27.7 (CH2),
77.4 (CHsp), 77.7 (Csp/CpC), 78.0 (Csp/CpC), 82.1 (Ccpd), 84.2
(η5-1-Trifluoromethylsulfonyloxy-2,3,4,5-tetraphenylcyclopentadi-
enyl)(η5-cyclopentadienyl)cobalt(III) Trifluoromethansulfonate (15):
The cyclopentadienone complex 14[16] (1 g, 1.9 mmol), dissolved in
dichloromethane (20 mL), was added to a cooled (–50 °C) solution
of trifluoromethanesulfonic anhydride (0.8 g, 2.9 mmol) in dry
dichloromethane (50 mL) over a period of 15 min. The mixture was
warmed and stirred for 12 h at room temperature. After evapora-
tion of the solvent, ether (100 mL) was added. The precipitate was
filtered off and recrystallized from CH2Cl2/Et2O to yield 15 (1.13 g,
75%) as a yellow solid; m.p. 189 °C. 1H NMR (500 MHz, CDCl3):
δ = 5.94 (s, 5 H, CpCH), 7.01–7.02 (m, 4 H, CHarom), 7.15–7.22 (m,
4 H, CHarom), 7.30–7.33 (m, 2 H, CHarom), 7.44–7.49 (m, 10 H,
CHarom) ppm. 13C NMR (125 MHz, CDCl3): δ = 90.7 (CpCH), 95.9
(Ccpd), 98.2 (Ccpd), 116.6 (COTf), 124.6 (Carom), 126.2 (Carom), 129.1
(CHarom), 129.4 (CHarom), 130.5 (CHarom), 131.1 (CHarom), 131.3
(CHarom), 131.3 (CHarom), 131.7 (CHarom) ppm. IR (KBr): ν = 3101
˜
(CpCH), 85.4 (CpCH), 93.0 (Ccpd), 159.3 (C=O) ppm. IR (KBr): ν
˜
(w), 2932 (s), 2861 (m), 1631 (m), 1464 (m), 1414 (s) cm–1. UV/Vis
(CH2Cl2): λmax (log ε) = 256 (4.28), 352 (4.09), 402 (3.43) nm.
HRMS (FAB): calcd. 641.0808; found 641.0815.
= 3061 (m), 2958 (s), 2934 (s), 2871 (m), 2098 (w), 1570 (vs), 1467
(m), 1229 (w), 1120 (w) cm–1. UV/Vis (CH2Cl2): λmax (log ε) = 298
(4.24), 368 (3.42), 416 (5.05) nm. HRMS (FAB): calcd. 397.1942;
found 397.1928. C24H33CoO (396.45): calcd. C 72.71, H 8.39;
found C 72.29, H 8.29.
Procedure for the (Trialkylsilyl)alkynyl-Substituted RCpCo-Capped
Cyclopentadienone Complexes 11a–11f and 12: n-Butyllithium
(2.29 mmol, 1.6  solution) was slowly added to a solution of (tri-
alkylsilyl)acetylene (3.06 mmol) in 60 mL of THF at –30 °C. The
mixture was stirred at this temperature for 90 min and then a solu-
tion of the cobaltocenium salt 8 (1.53 mmol) in THF (30 mL) was
added over a period of 10 min. After it was warmed overnight and
stirred further at room temperature for 48 h, the mixture was hy-
drolyzed with a saturated NH4Cl solution (30 mL), the layers were
separated, and the aqueous layer was washed three times with
ether. Once the combined organic layers had been dried with
MgSO4, the solvent was removed and the crude mixture was puri-
fied by column chromatography on silica gel with CH2Cl2/MeOH
(30:1).
[(2,3,4,5-η)-2,3,4,5-Tetrapropylcyclopenta-2,4-dien-1-one](η5-tri-
methylsilylethynylcyclopentadienyl)cobalt(I) (11a): Complex 11a
(114 mg, 16%) was obtained as a dark-red oil. 1H NMR (500 MHz,
CD2Cl2): δ = 0.25 [s, 9 H, Si(CH3)3], 0.96–1.04 (m, 12 H, CH3),
1.45–1.49 (m, 6 H, CH2), 1.63–1.65 (m, 2 H, CH2), 1.90–1.93 (m,
2 H, CH2), 2.27–2.43 (m, 6 H, CH2), 4.61–4.62 (m, 2 H, CpCH),
4.73–4.74 (m, 2 H, CpCH) ppm. 13C NMR (125 MHz, CD2Cl2): δ
[(2,3,4,5-η)-2,3,4,5-Tetrapropylcyclopenta-2,4-dien-1-one](η5-tri-
methylsilylbutadiynylcyclopentadienyl)cobalt(I) (11d): MeLi/LiBr
(2.53 mmol, 1.5  in THF) was added to a solution of bis(trime-
thylsilyl)acetylene (446 mg, 2.3 mmol) in ether (50 mL) at room
temperature. After the mixture was stirred at this temperature over-
night, it was cooled to –50 °C and a solution of the cobaltocenium
salt 8 (1 g, 1.53 mmol) in THF (30 mL) was added over a period
of 10 min. After it was warmed overnight and stirred further at
room temperature for 48 h, the mixture was hydrolyzed with a satu-
rated NH4Cl solution (30 mL), the layers were separated, and the
aqueous layer was washed three times with ether. The combined
organic layers were dried with MgSO4, the solvent was removed,
and the crude mixture was purified by column chromatography on
silica gel with CH2Cl2/MeOH (30:1). Complex 11d (83 mg, 11%)
1
was obtained as a dark-red oil. H NMR (500 MHz, CDCl3): δ =
0.20 [s, 9 H, Si(CH3)3], 0.96–0.99 (t, 6 H, CH3), 1.00–1.03 (t, 6 H,
CH3), 1.40–1.49 (m, 6 H, CH2), 1.64–1.72 (m, 2 H, CH2), 1.84–
1.89 (m, 2 H, CH2), 2.20–2.27 (m, 2 H, CH2), 2.33–2.44 (m, 4 H,
= –0.4 [Si(CH3)3], 14.5 (CH3), 14.6 (CH3), 22.6 (CH2), 24.2 (CH2), CH2), 4.67–4.68 (m, 2 H, CpCH), 4.76–4.77 (m, 2 H, CpCH) ppm.
27.0 (CH2), 27.1 (CH2), 78.7 (Csp), 82.6 (C), 84.2 (CpCH), 85.0 13C NMR (125 MHz, CDCl3): δ = –0.3 [Si(CH3)3], 15.0 (CH3), 15.1
(CpCH), 92.7 (C), 94.7 (C), 98.5 (C), 157.0 (C=O) ppm. IR (KBr):
(CH3), 22.7 (CH2), 24.3 (CH2), 27.6 (CH2), 27.6 (CH2), 70.7 (Csp),
71.7 (Csp), 74.1 (Csp), 76.6 (Csp), 82.7 (Ccpd/CpC), 84.9 (CpCH), 85.6
(CpCH), 87.8 (Ccpd/CpC), 93.2 (Ccpd/CpC), 159.4 (C=O) ppm.
HRMS (FAB): calcd. 493.2337; found 493.2325.
ν = 2960 (vs), 2933 (s), 2872 (s), 2152 (m), 1557 (vs), 1456 (s), 1250
˜
(s) cm–1. UV/Vis (CH2Cl2): λmax (log ε) = 302 (4.18), 370 (3.45),
412 (3.09) nm. HRMS (FAB): calcd. 469.2337; found 469.2339.
Eur. J. Inorg. Chem. 2008, 2664–2669
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M. von der Grün, R. Gleiter, F. Rominger
FULL PAPER
[(2,3,4,5-η)-2,3,4,5-Tetrapropylcyclopenta-2,4-dien-1-one](η5-tri-
ethylsilylbutadiynylcyclopentadienyl)cobalt(I) (11e): nBuLi
(0.95 mmol, 1.6  in n-hexane) was slowly added to a solution of
the complex 11c (341 mg, 0.86 mmol) in THF (50 mL) at –35 °C.
Subsequently, CuI (164 mg, 0.86 mmol) was added and the mixture
was stirred for 10 min at –15 °C. After stirring at room temperature
for 10 min, the suspension was cooled to –25 °C and freshly dis-
tilled ethylamine (2 mL) as well as bromo(triethylsilyl)acetylene
(208 mg, 0.95 mmol) in THF (5 mL) were added. After further stir-
ring for 12 h, the hydrolysis was carried out with 50 mL of satu-
rated NH4Cl solution. The workup was completed by extraction of
the aqueous layer with ether and drying of the combined organic
layers with MgSO4. Purification by column chromatography on sil-
ica gel with CH2Cl2/MeOH (30:1) yielded the complex 11e (349 mg,
λmax (log ε) = 270 (4.23), 346 (4.11), 402 (2.97) nm. HRMS (FAB):
calcd. 605.1710; found 605.1736.
Procedure for the Alkyne-Bridged Cyclopentadienone Complexes 13a
and 13b: A solution of CuCl [13a: 15 mg (0.15 mmol), 13b: 10 mg
(0.10 mmol)] in dry pyridine (15 mL), saturated with oxygen, was
added to a Schlenk flask. The alkynyl complex [11c: 150 mg
(0.38 mmol), 11f: 105 mg (0.25 mmol)] was added to this mixture
and oxygen was passed through the mixture for 24 h. After removal
of the pyridine under vacuum, the crude product was purified by
column chromatography on neutral alumina, activity III, CH2Cl2/
MeOH (50:1).
Bis{[(2,3,4,5-η)-2,3,4,5-tetrapropylcyclopenta-2,4-dien-1-one](η5-eth-
ynylcyclopentadienyl)cobalt(I)} (13a): Complex 13a (119 mg, 79%)
was obtained as a dark-red solid; m.p. 166 °C. 1H NMR (500 MHz,
CDCl3): δ = 0.96 (t, 12 H, CH3), 1.0 (t, 12 H, CH3), 1.41–1.48 (m,
12 H, CH2), 1.65–1.71 (m, 4 H, CH2), 1.83–1.89 (m, 4 H, CH2),
2.22–2.28 (m, 4 H, CH2), 2.34–2.44 (m, 8 H, CH2), 4.71–4.76 (m,
8 H, CpCH) ppm. 13C NMR (125 MHz, CDCl3): δ = 15.0 (CH3),
15.1 (CH3), 22.6 (CH2), 24.3 (CH2), 27.6 (CH2), 27.7 (CH2), 73.9
(Csp/CpC), 75.4 (Csp/CpC), 77.0 (Csp/CpC), 82.8 (Ccpd), 84.9 (CpCH),
1
79%) as a dark-red oil. H NMR (500 MHz, CDCl3): δ = 0.66 (q,
6 H, SiCH2), 0.99 (t, 9 H, SiCH2CH3), 1.02 (t, 6 H, CH3), 1.04 (t,
6 H, CH3), 1.43–1.53 (m, 6 H, CH2), 1.67–1.74 (m, 2 H, CH2),
1.87–1.93 (m, 2 H, CH2), 2.24–2.30 (m, 2 H, CH2), 2.37–2.48 (m,
4 H, CH2), 4.72–4.73 (m, 2 H, CpCH), 4.80–4.81 (m, 2 H,
CpCH) ppm. 13C NMR (125 MHz, CDCl3): δ = 4.3 (SiCH2), 7.5
(SiCH2CH3), 15.0 (CH3), 15.1 (CH3), 22.7 (CH2), 24.3 (CH2), 27.6
(CH2), 27.7 (CH2), 70.9 (Csp), 74.4 (Csp), 76.8 (Csp), 83.0 (C), 85.0
(CpCH), 85.6 (CpCH), 88.2 (C), 88.9 (C), 93.3 (C), 158.7
85.5 (CpCH), 93.2 (Ccpd), 159.2 (C=O) ppm. IR (KBr): ν = 2960
˜
(m), 2933 (s), 2871 (m), 2151 (w), 1588 (vs), 1464 (s), 1379 (m),
1119 (m) cm–1. UV/Vis (CH2Cl2): λmax (log ε) = 286 (4.48), 382
(4.02), 442 (3.55) nm. HRMS (FAB): calcd. 791.3649; found
791.3662.
(C=O) ppm. IR (film): ν = 3099 (w), 2958 (vs), 2873 (vs), 2208
˜
(s), 2104 (m), 1567 (vs), 1466 (s), 1378 (w), 1235 (w) cm–1. UV/Vis
(CH2Cl2): λmax (log ε) = 274 (4.07), 298 (4.19), 308 (4.20), 376
(3.58), 420 (3.12) nm. HRMS (FAB): calcd. 535.2806; found
535.2809.
Bis{[(2,3,4,5-η)-2,3,4,5-tetrapropylcyclopenta-2,4-dien-1-one](η5-
butadiynylcyclopentadienyl)cobalt(I)} (13b): Complex 13b (93 mg,
89%) was obtained as a dark-red solid; m.p. 159 °C. 1H NMR
(500 MHz, CD2Cl2): δ = 0.99 (t, 12 H, CH3), 1.04 (t, 12 H, CH3),
1.39–1.53 (m, 12 H, CH2), 1.60–1.70 (m, 4 H, CH2), 1.85–1.91 (m,
4 H, CH2), 2.24–2.45 (m, 12 H, CH2), 4.80–4.81 (m, 8 H,
CpCH) ppm. 13C NMR (125 MHz, CD2Cl2): δ = 14.9 (CH3), 15.0
(CH3), 22.8 (CH2), 24.6 (CH2), 27.8 (CH2), 27.9 (CH2), 63.9 (Csp),
66.3 (Csp/CpC), 74.0 (Csp/CpC), 74.0 (Csp/CpC), 75.8 (Csp/CpC), 82.8
(Ccpd), 85.6 (CpCH), 86.4 (CpCH), 94.1 (Ccpd), 159.6 (C=O) ppm.
[(2,3,4,5-η)-2,3,4,5-Tetrapropylcyclopenta-2,4-dien-1-one](η5-buta-
diynylcyclopentadienyl)cobalt(I) (11f): nBu4NF (0.74 mmol, 1.5  in
THF) was added to a solution of 11e (358 mg, 0.67 mmol) in THF
(10 mL). After 5 h the mixture was hydrolyzed with a saturated
NH4Cl solution (30 mL), the layers were separated, and the aque-
ous layer was washed three times with ether. The combined organic
layers were dried with MgSO4, the solvent was removed, and the
crude mixture was purified by column chromatography on silica
gel with CH2Cl2/MeOH (20:1). Complex 11f (182 mg, 65%) was
obtained as a dark-red air-sensitive solid; m.p. 124 °C. 1H NMR
(500 MHz, CD2Cl2): δ = 0.98 (t, 6 H, CH3), 1.03 (t, 6 H, CH3),
1.42–1.52 (m, 6 H, CH2), 1.62–1.68 (m, 4 H, CH2), 1.85–1.90 (m,
2 H, CH2), 2.24–2.44 (m, 4 H, CH2), 2.57 (s, 1 H, CϵCH), 4.74–
4.75 (m, 4 H, CpCH) ppm. 13C NMR (125 MHz, CD2Cl2): δ = 15.0
(CH3), 15.1 (CH3), 22.8 (CH2), 24.6 (CH2), 27.7 (CH2), 27.9 (CH2),
68.2 (CHalkyne), 70.7 (Csp/CpC),70.7 (Csp/Cpc), 73.2 (Csp/CpC), 76.4
(Csp/CpC), 82.6 (Ccpd), 85.0 (CpCH), 86.0 (CpCH), 93.7 (Ccpd), 159.5
IR (KBr): ν = 3066 (w), 2959 (vs), 2932 (s), 2870 (s), 2198 (vs),
˜
2123 (w), 2077 (w), 1592 (vs), 1466 (s), 1377 (m) cm–1. UV/Vis
(CH2Cl2): λmax (log ε) = 244 (4.79), 258 (4.79), 312 (4.78), 334
(4.68), 398 (4.43), 430 (4.30), 488 (3.94) nm. HRMS (FAB): calcd.
839.3649; found 839.3680.
X-ray Structure Analyses: The reflections were collected with a
Bruker Smart CCD diffractometer at 200 K equipped with a Mo-
Kα radiation source and
a graphite monochromator (λ =
0.71073 Å). The 0.3° omega-scans that were taken covered a whole
sphere in reciprocal space in each case. Intensities were corrected
for Lorentz and polarization effects, and an absorption correction
was applied using the SADABS program based on the Laue sym-
metry of the reciprocal space, except for 13a where no absorption
correction was applied because of insufficient data quality. The
structures were solved by direct methods, and the structural param-
eters of the non-hydrogen atoms were refined anisotropically ac-
cording to a full-matrix least-squares technique against F2. All hy-
drogen atoms were treated using appropriate riding models. Struc-
ture solution and refinement were carried out with the SHELXTL
(5.10) software package.[22]
(C=O) ppm. IR (film): ν = 3071 (m), 2960 (s), 2931 (s), 2870 (m),
˜
2213 (w), 2045 (w), 1627 (m), 1573 (vs), 1463 (m) cm–1. UV/Vis
(CH2Cl2): λmax (log ε) = 266 (4.14), 300 (4.39), 360 (3.72), 374
(3.80), 418 (3.72) nm. HRMS (FAB): calcd. 421.1942; found
421.1942.
[(2,3,4,5-η)-2,3,4,5-Tetraphenylcyclopenta-2,4-dien-1-one](η5-tri-
methylsilylethynylcyclopentadienyl)cobalt(I) (12): Complex 12
(87 mg, 19%) was obtained as a dark-red solid; m.p. 208 °C. 1H
NMR (500 MHz, CD2Cl2): δ = 0.12 [s, 12 H, Si(CH3)3], 4.91–4.92
(m, 2 H, CpCH), 4.94–4.96 (m, 2 H, CpCH), 7.15–7.29 (m, 16 H,
CHarom), 7.60–7.62 (m, 4 H, CHarom) ppm. 13C NMR (125 MHz,
Crystallographic data and details of the data collection and the
CD2Cl2): δ = –0.4 [Si(CH3)3], 78.9 (Csp), 81.9 (C), 87.3 (CpCH), refinement procedure are given below. CCDC-674040 (for 7),
87.4 (CpCH), 94.3 (C), 97.9 (C), 98.1 (C), 127.5 (CHarom), 127.9 -674041 (for 8), -674042 (for 12), -674043 (for 11c), -674044 (for
(CHarom), 128.0 (CHarom), 128.1 (CHarom), 131.0 (CHarom), 132.1 11f), and -674045 (for 13a) contain the supplementary crystallo-
(CHarom), 132.2 (Carom), 133.0 (Carom), 157.0 (CO) ppm. IR (KBr): graphic data for this paper. These data can be obtained free of
ν = 3042 (w), 2919 (m), 2850 (m), 1634 (s), 1545 (w), 1502 (w), charge from The Cambridge Crystallographic Centre via
˜
1462 (w), 1447 (w), 1385 (w), 1250 (m) cm–1. UV/Vis (CH2Cl2): www.ccdc.cam.ac.uk/conts/retrieving.html (or, 12 Union Road,
2668
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 2664–2669

Alkyne Substitution on Cobaltocenium Triflates
Cambridge CB2 1EZ, UK; Fax: +44-1223-336033; E-mail: = 0.092, wR(F2) = 0.242 for observed reflections, residual electron
deposit@ccdc.cam.ac.uk).
density –1.18 to 2.98 eÅ–3.
7: Orange crystal (needle), dimensions 0.41ϫ0.10ϫ0.08 mm, crys-
tal system monoclinic, space group P21/c, Z = 8, a = 7.8532(1) Å,
b = 19.0327(3) Å, c = 27.5571(3) Å, α = 90°, β = 90.5370(10)°, γ
= 90°, V = 4118.71(9) Å3, ρ = 1.201 gcm–3, θmax = 26.35°, 39017
reflections measured, 8397 unique [R(int) = 0.0714], 5504 observed
[IϾ2σ(I)], µ = 0.84 mm–1, Tmin = 0.73, Tmax = 0.94, 433 parameters
refined, goodness of fit 1.01 for observed reflections, final residual
values R(F) = 0.040, wR(F2) = 0.074 for observed reflections, resid-
ual electron density –0.29 to 0.27 eÅ–3.
Acknowledgments
Financial support from the Deutsche Forschungsgemeinschaft
(DFG) is gratefully acknowledged. We thank Mrs. P. Krämer for
typing the manuscript and for drawing the schemes.
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8: Yellow crystal (polyhedron), dimensions 50ϫ26ϫ15 mm, crys-
tal system monoclinic, space group P21/n, Z = 4, a = 13.9634(2) Å,
b = 12.8101(2) Å, c = 16.9600(2) Å, α = 90°, β = 106.755(1)°, γ
= 90°, V = 2904.89(7) Å3, ρ = 1.497 gcm–3, θmax = 27.48°, 29561
reflections measured, 6655 unique [R(int) = 0.0377], 5340 observed
[IϾ2σ(I)], µ = 0.81 mm–1, Tmin = 0.75, Tmax = 0.89, 386 parameters
refined, goodness of fit 1.03 for observed reflections, final residual
values R(F) = 0.031, wR(F2) = 0.077 for observed reflections, resid-
ual electron density –0.29 to 0.40 eÅ–3.
11c: Orange crystal (polyhedron), dimensions 32ϫ16ϫ07 mm,
crystal system monoclinic, space group P21/c, Z = 4, a =
13.3378(1) Å, b = 7.8770(1) Å, c = 21.1540(3) Å, α = 90°, β =
101.9460(10)°, γ = 90°, V = 2174.35(4) Å3, ρ = 1.211 gcm–3, θmax
= 27.48°, 21820 reflections measured, 4982 unique [R(int) =
0.0495], 3695 observed [IϾ2σ(I)], µ = 0.80 mm–1, Tmin = 0.74, Tmax
= 0.95, 244 parameters refined, goodness of fit 1.02 for observed
reflections, final residual values R(F) = 0.036, wR(F2) = 0.076 for
observed reflections, residual electron density –0.34 to 0.26 eÅ–3.
11f: Red crystal (polyhedron), dimensions 0.45ϫ0.26ϫ0.14 mm,
crystal system monoclinic, space group P21/c, Z = 8, a =
[13] M. Sato, Y. Kubota, Y. Kawata, T. Fujihara, K. Unoura, A.
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17.5063(3) Å,
b = 15.8730(3) Å, c = 18.9913(3) Å, β =
117.2720(10)°, V = 4690.64(14) Å3, ρ = 1.191 gcm–3, θmax = 27.46°,
47930 reflections measured, 10738 unique [R(int) = 0.0530], 6874
observed [IϾ2σ(I)], µ = 0.74 mm–1, Tmin = 0.71, Tmax = 0.91, 513
parameters refined, goodness of fit 1.02 for observed reflections,
final residual values R(F) = 0.037, wR(F2) = 0.083 for observed
reflections, residual electron density –0.53 to 0.47 eÅ–3.
[14] S. Szafert, J. A. Gladysz, Chem. Rev. 2003, 103, 4175–4205 and
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1955, 241, 1055–1057; b) P. Cadiot, W. Chodkiewicz in Chemis-
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2000, 19, 1578–1588.
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[22] G. M. Sheldrick, Bruker Analytical X-ray Division, Madison,
Wisconsin 1997.
12:
Dark-red
crystal
(polyhedron),
dimensions
¯
0.38ϫ0.22ϫ0.13 mm, crystal system triclinic, space group P1,
Z = 2, a = 10.0788(3) Å, b = 12.6156(3) Å, c = 13.4032(3) Å, α =
76.4710(10)°,
β
=
71.8860(10)°,
γ
=
81.5640(10)°, V =
1569.76(7) Å3, ρ = 1.279 gcm–3, θmax = 27.50°, 15558 reflections
measured, 7123 unique [R(int) = 0.0293], 5642 observed [IϾ2σ(I)],
µ = 0.61 mm–1, Tmin = 0.77, Tmax = 0.93, 382 parameters refined,
goodness of fit 1.02 for observed reflections, final residual values
R(F) = 0.034, wR(F2) = 0.079 for observed reflections, residual elec-
tron density –0.41 to 0.28 eÅ–3.
13a: Red crystal (polyhedron), dimensions 0.16ϫ0.29ϫ0.50 mm,
crystal system monoclinic, space group C2/c, Z = 24, a =
23.3709(3) Å,
b = 40.0736(5) Å, c = 32.4767(4) Å, β =
110.0080(10)°, V = 28580.5(6) Å3, ρ = 1.279 gcm–3, θmax = 23.26°,
105915 reflections measured, 20533 unique [R(int) = 0.1542], 10978
observed [IϾ2σ(I)], µ = 0.91 mm–1, 1551 parameters refined, good-
ness of fit 1.01 for observed reflections, final residual values R1(F)
Received: January 24, 2008
Published Online: April 30, 2008
Eur. J. Inorg. Chem. 2008, 2664–2669
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2669