The ferrocenyldiphenylpropargyl cation - A spectroscopic comparison among stabilizing substituents and nucleophilic additions

Article abstract of DOI:10.1002/1099-0682(200009)2000:9<2003::aid-ejic2003>3.0.co;2-q

The stable ferrocenyldiphenylpropargyl cation (3) is readily and quantitatively generated from the propargylic alcohol 2 with a slight excess of tetrafluoroboric acid in dichloromethane at -78 °C. The cationic species 3 was characterized by ¹H- and ¹³C-NMR spectroscopy; nucleophilic trapping reactions gave rise to the formation of ferrocenyldiphenylallenes 9.

Full text of DOI:10.1002/1099-0682(200009)2000:9<2003::aid-ejic2003>3.0.co;2-q

FULL PAPER
The Ferrocenyldiphenylpropargyl Cation ؊ A Spectroscopic Comparison
Among Stabilizing Substituents and Nucleophilic Additions
Markus Ansorge,[a] Kurt Polborn,[a] and Thomas J. J. Müller*[a]
Keywords: Ferrocene / Cations / Allenes / Pi interactions / NMR spectroscopy
The stable ferrocenyldiphenylpropargyl cation (3) is readily
and quantitatively generated from the propargylic alcohol 2
1H- and 13C-NMR spectroscopy; nucleophilic trapping reac-
tions gave rise to the formation of ferrocenyldiphenylall-
with a slight excess of tetrafluoroboric acid in dichlorome- enes 9.
thane at −78 °C. The cationic species 3 was characterized by
Introduction
ferrocene as the stabilizing organometallic moiety in com-
parison to carbonylchromium-complexed arenes. Here, we
wish to report our results on the spectroscopic characteriza-
tion and nucleophilic trapping reactions of the stable ferro-
cenyldiphenylpropargyl cation[8] as well as on the spectro-
scopic comparison to the uncomplexed[9] and tricarbon-
ylchromium-complexed[5b] phenyl analog.
The discovery of transition metal stabilization of reactive
intermediates[1] has not only initiated a remarkable theoret-
ical interest but has also had a tremendous impact on the
application of such species in synthetic chemistry, namely
the synthesis of complex organic molecules.[2] Thus, carben-
ium ions can be stabilized by quite a number of organomet-
allic substituents such as metallocene and half-sandwich
complexes, particularly ferrocenyl, tricarbonylcyclobutadi-
enyliron, cyclobutadienylcyclopentadienylcobalt, and ben-
zenecarbonylchromium derivatives.[1,2] Electronically, this
stabilization of cationic charges in the α-position of organo-
metallic fragments can be rationalized by a strong dϪp
overlap from the transition metal centered occupied d or-
bitals to the vacant pz orbital at the carbenium site, accom-
panied by a pronounced bending of the cationic side chain
towards the metal center.[1a,1d,3] As a consequence, this
strong electronic interaction manifests itself as a configura-
tional and conformational fixation of the positively charged
substituent and, ultimately, leads to highly stereoselective
nucleophilic additions.
Results and Discussion
Generation of the Ferrocenyldiphenylpropargyl Cation (3)
Generally, propargyl cations can be generated from the
corresponding propargyl derivatives with suitable leaving
groups upon treatment with Lewis or Brønsted acids, in
particular, this can be achieved in a fairly facile way upon
acid-mediated ionization of propargyl alcohols. According
to the synthesis of highly stable perferrocenylated propargyl
cations by Bildstein,[10] our strategy towards ferrocenyl-sub-
stituted γ-propargyl cations commences with the addition
of ferrocenyl acetylide [by deprotonation of ethynylferro-
cene (1) with butyllithium] to benzophenone to give the
propargyl alcohol 2 in good yield (Scheme 1). Treatment of
the propargylic alcohol 2 with a 1.5-fold excess of tetra-
fluoroboric acidϪdiethyl ether in dichloromethane solution
at Ϫ78 °C[5b] led to the formation of a deep-green solution
of the persistent allenyl/propargyl cation 3 in quantitative
yield (according to NMR and UV/Vis spectroscopy, vide
infra) within 5 min.
Although quite a number of substituted carbenium ions[4]
have been known for some time, the investigation of the
chemistry of transition metal stabilized cations with conjug-
ated substituents, i.e. ambident electrophiles, is still in its
infancy.[5] Recently, we showed that arenecarbonylchrom-
ium fragments efficiently stabilize α- and γ-propargyl cat-
ions and that α-propargyl cations can be trapped with nu-
cleophiles to give arene complex substituted propargyl de-
rivatives with excellent diastereoselectivity.[6] In particular,
the peculiar ability to stabilize a cationic charge generated
in the γ-position to the stabilizing substituent, as well as the
ambident reactivity of propargyl cations giving rise either
to allenes or alkynes,[7] prompted us to study the structure
(UV/Vis and 13C-NMR spectroscopy) and reactions of a
related propargyl cation bearing the more powerful donor
[a]
Department Chemie der Ludwig-Maximilians-Universität
München
Butenandtstrasse 5Ϫ13 (Haus F), D-81377 München, Germany
E-mail: tom@cup.uni-muenchen.de
Scheme 1
Eur. J. Inorg. Chem. 2000, 2003Ϫ2009
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
1434Ϫ1948/00/0909Ϫ2003 $ 17.50ϩ.50/0
2003

M. Ansorge, K. Polborn, T. J. J. Müller
FULL PAPER
Structure of the Propargyl Cation 3
As expected, and in agreement with cation generation
studies of related propargyl cations,[5][9a] the ionization of
the propargyl alcohol 2 to give the propargyl cation 3 re-
sults in a considerable downfield shift of almost all signals
in the proton and carbon NMR spectra (Figure 1 and Fig-
ure 2, Table 1). Only the ipso-phenyl carbon resonance of 3
(δ ϭ 141.52, ∆I ϭ Ϫ3.35) is shifted to high field, indicating
an adjacent carbenium center. Thus, the positive charge is
delocalized by resonance stabilization over the complete
side chain including the substituted cyclopentadienyl li-
gand. Even the unsubstituted cyclopentadienyl ring of 3
(1H: δ ϭ 4.96, ∆I ϭ ϩ0.72; 13C: δ ϭ 81.75, ∆I ϭ ϩ12.15),
and with it the ferrocenyl iron atom, experiences a signific-
ant downfield shift of the resonances, indicating their parti-
cipation in the extensive charge stabilization. Most signific-
antly, the downfield shifts of the carbon resonances of the
quaternary signals of the propargyl/allenyl side chain reveal
a dominant contribution of the allenylium canonical reson-
ance structure 3B to the stabilization of the cation gener-
ated at the γ-position as compared to the ferrocenyl moiety.
Figure 2. 13C-NMR spectra of 2 (top) and 3 (bottom) (Ϫ70 °C,
CD2Cl2, 100 MHz)
Table 1. Assignment and ionization shifts of 1H- (400 MHz) and
13C-NMR (100 MHz) signals (CD2Cl2, Ϫ70 °C) of 2 and 3
1
Figure 2. H-NMR spectra (Ϫ70 °C, CD2Cl2, 400 MHz) of 2 (top)
and 3 (bottom)
A comparison of the carbon resonances of the propargyl
cation bridge and the γ-terminal p-phenyl positions of the
cations 4 (i.e., 5,[9a] 6,[5b] and 3) reveals the increasing con-
2004
Eur. J. Inorg. Chem. 2000, 2003Ϫ2009

The Ferrocenyldiphenylpropargyl Cation
FULL PAPER
Table 2. Selected carbon resonances of the propargylic cations 4
(i.e., 5,[9a] 6,[5b] and 3) and the reference compounds 7[11] and 8[12]
Figure 3. Correlation of the ∆π values (∆π ϭ δpara Ϫ δmeta) and
the Cγ resonance (carbenium or quaternary benzyl center) of the
propargyl cations 3, 5, 6, and the resonance compounds 7 and 8
charge (Figure 3). According to a lever-rule model[5b,9a] the
relative contributions of mesomeric forms to the stabiliza-
tion of resonance-stabilized cations can be estimated by
considering the Cγ-carbenium resonances or the p-phenyl
carbon signal.[13] On applying the Cγ resonances the contri-
[a]
[b]
FSO3HϪSbF5ϪSO2, Ϫ60 °C. Ϫ
°C.
CD2Cl2 ϩ HBF4OEt2, Ϫ70
tribution of the allenylium resonance structure 4B upon bution of the α-substituent stabilization increases from 10
varying the α-substituent from phenyl (5) to the organomet- (5) to 59 (6) to 79% (3), whereas consideration of the para
allic donors (OC)3(Ph)Cr (6) and ferrocenyl (3) (Table 2). resonances gives rise to a 29 (5), 60 (6), and 78% (3) parti-
More specifically, the α-, γ- and terminal p-phenyl reson- cipation of the allenylium canonical structure 8B in the elec-
ances decrease in this order, indicating a charge delocaliz- tronic ground state.
ation shift towards the α-substituent fragment. Simultan-
Ionization with tetrafluoroboric acidϪdiethyl ether of a
eously, the β-resonances increase towards an ‘‘allenic’’ dir- dichloromethane solution of 2 at Ϫ70 °C leads to a color
ection. As reference systems for localized cations, the change from yellow/orange to deep green. This change can
benzylhydryl cation (7)[11] represents a model for a carben- be monitored by following the appearance of long-wave-
ium ion only delocalized at the Cγ position and its phenyl length absorption bands with maxima at 310 (sh), 412, 483,
substituents, as depicted in structure 4A, whereas 1,1-di- and 856 nm (Figure 4) by UV/Vis spectroscopy. According
phenylethene (8)[12] serves as a model for an allenylium to calculations on an MM2-optimized structure of 2 using
structure (4B) assuming the γ-carbon atom does not bear a the ZINDO/CI formalism with INDO/1 parameters[14]
positive charge and the charge is completely stabilized at the absorptions at 856 nm (calcd. 688 nm; iron-centered
2
2
the Cα position.
dx Ϫy orbital HOMO to the localized LUMO of the pro-
2
A linear correlation between the Cγ resonance (carben- pargyl moiety), at 483 nm (calcd. 484 nm; dz orbital
ium or quaternary benzyl center) and the ∆π values (∆π ϭ HOMO-2 to the LUMO) and at 412 nm (calcd. 389 nm, dxz
2
δpara Ϫ δmeta) of the propargyl cations 4 and the reference orbital HOMO-3 to LUMO and calcd. 403 nm, dz orbital
compounds 7 and 8 establishes the dominant influence of HOMO-2 to LUMO) and at 310 nm (sh) [calcd. 326 nm,
the α-substituent on the π-delocalization of the positive bound Cp ring (HOMO-8) to propargyl fragment (LUMO)
Figure 4. UV/Vis spectra of 2 (λmax at 270 and 446 nm) and 3 (λmax at 310sh, 412, 483, and 483 nm) at Ϫ70 °C (dichloromethane)
Eur. J. Inorg. Chem. 2000, 2003Ϫ2009
2005

M. Ansorge, K. Polborn, T. J. J. Müller
FULL PAPER
π-π* transition and calcd. 311 nm, from the phenyl rings to Table 3. Crystal data and structure refinements for 9b
the propargyl fragment (HOMO-10 to LUMO)] are read-
ily reproduced.
9b
Empirical formula
Molecular mass
Temperature
C30H28FeO2
476.37
Nucleophilic Trapping Reactions of 3
298(2) K
The propargyl cation 3 can be trapped with different nu-
cleophiles to furnish the allenes 9 in good to excellent yields
(Scheme 2). Most interestingly, if ethanol is used as the nu-
cleophile only the hydrolysis product, i.e. the enone 10, can
be isolated (70% yield). In significant contrast to the cations
5 and 6, where the kinetically controlled ethanol attack
gives rise to the formation of the corresponding propargyl
ethers,[5b,15] the regioselectivity of the nucleophilic attack of
ethanol on 3 is reversed to the α-position, which results in
the generation of the allene intermediate 9d. The increasing
contribution of the allenylium canonical structure 4B (vide
supra) to the electronic ground state of 3 can be interpreted
˚
Radiation
0.71073 A; Mo-Kα
Crystal system
Space group
Unit cell dimensions [A]
triclinic
¯
P1
˚
a ϭ 8.8576(17); α ϭ 64.201(7),
b ϭ 11.7194(7); β ϭ 75.284(12),
c ϭ 13.3764(15); γ ϭ 84.435(9)
1209.0(3)
3
˚
Volume [A ]
Z
2
Density (calculated)
Absorption correction
Absorption coefficient
Max. and min. transmission
F(000)
1.309 g/cm3
ω2θ-scans
0.648 mmϪ1
0.9994 and 0.9556
500
Crystal size [mm]
2θ range (min./max.)
Index ranges
0.20 ϫ 0.27 ϫ 0.53
2.38/23.97°
Ϫ10 Յ h Յ 10; 0 Յ k Յ 13
Ϫ13 Յ l Յ 15
3989
as an increase of the orbital coefficient at the α-position in Reflections collected
Independent reflections
the LUMO, the relevant orbital for kinetically controlled
Observed reflections
3781 [R(int) ϭ 0.0087]
3270 [I Ͼ 2σ(I)]
SHELXL-93 on F2
3781/0/301
nucleophilic additions to the cations 4.
Refinement method
Data/restraints/parameters
Goodness of fit on F2
1.092
Final R indices [I Ͼ 2σ(I)]
R1
wR2
0.0322
0.0793
R indices (all data)
R1
wR2
0.0391
0.0841
3
˚
Largest diff. peak and hole [e/A ] 0.194 and Ϫ0.252
Scheme 2
Due to the pronounced basicity the ferrocenyl-substi-
tuted allenes 9 tend to form ferrocenylallyl cations revers-
ibly.[16] Only if the basicity is modulated by an electron-
withdrawing group (9a), or if acid-sensitive nucleophiles,
such as silyl enol ethers or silyl ketene acetals, successfully
trap excess protons, by acting as proton sponges, can the
formation of allyl cations be prevented.
˚
Figure 5. ORTEP plot of 9b; selected bond lengths [A], bond angles
The structural assignments of the allenes 9aϪc are fully
supported by NMR, IR, elemental analysis and by an X-
ray crystal structure analysis of 9b (Figure 5, Table 3).[17] In
[°] and torsional angles [°]: C(1)ϪC(11) 1.482(3), C(11)ϪC(12)
1.312(3), C(12)ϪC(13) 1.316(3), C(1)ϪC(5) 1.431(3), C(4)ϪC(5)
1.412(3); C(12)ϪC(11)ϪC(1) 119.8(2), C(12)ϪC(11)ϪC(26)
119.9(2), C(11)ϪC(12)ϪC(13) 175.0(2); C(11)ϪC(1)ϪC(2)ϪC(3)
1
the H-NMR spectra the signals of the ferrocene protons
175.2(2),
C(2)ϪC(1)ϪC(11)ϪC(12)
4.1(3),
C(2)ϪC(1)Ϫ
appear between δ ϭ 3.92 and 4.34. Most characteristically, C(11)ϪC(26) 176.9(2)
2006
Eur. J. Inorg. Chem. 2000, 2003Ϫ2009

The Ferrocenyldiphenylpropargyl Cation
FULL PAPER
the 13C-NMR signals of the central allene carbon atoms
are found between δ ϭ 204.6 and 216.7 depending on the
electronic nature of the substituent at the α-position. Ac-
cording to the X-ray crystal structure analysis (Figure 5) of
was added dropwise a solution of 0.89 g (4.90 mmol) of benzo-
phenone in 5 mL of THF and, after the addition, the mixture was
allowed to warm up to room temperature over a period of 60 min.
After the addition of 20 mL of water and extraction of the aqueous
phase with diethyl ether (3 ϫ 50 mL), the combined organic phases
were dried with magnesium sulfate. After evaporation of the solv-
ents, the residue was purified by chromatography on silica gel with
a gradient of diethyl ether/pentane (1:10 Ǟ 1:1) to afford 1.42 g
(74%) of the propargylic alcohol 2 as an orange crystalline product,
the allene
9b, the allene moiety
is linear
[C(11)ϪC(12)ϪC(13): 175°] and the allenic double bond
˚
˚
lengths [C(11)ϪC(12): 1.31 A and C(12)ϪC(13): 1.32 A] lie
within the expected range. Interestingly, the cyclo-
pentadienyl ring and the allene fragment are arranged in an
1
m.p. 90Ϫ92 °C. Ϫ H NMR ([D6]DMSO, 300 MHz): δ ϭ 4.25 (s,
almost coplanar manner, although the ferrocenyl substitu- 5 H), 4.29 (d, J ϭ 1.7 Hz, 2 H), 4.53 (dd, J ϭ 1.7 Hz, 2 H), 6.74
(s, 1 H), 7.22 (m, 2 H), 7.33 (m, 4 H), 7.60 (m, 4 H); (CD2Cl2,
400 MHz): δ ϭ 3.29 (s, 1 H), 4.24 (s, 5 H), 4.25 (m, 2 H), 4.52 (m,
2 H), 7.28 (t, J ϭ 7.3 Hz, 2 H), 7.36 (dd, J ϭ 7.3 Hz, 4 H), 7.68
(d, J ϭ 7.8 Hz, 4 H). Ϫ 13C NMR ([D6]DMSO, 75 MHz): δ ϭ 64.5
(Cquat.), 69.0 (CH), 69.8 (CH), 71.3 (CH), 73.4 (Cquat.), 84.6 (Cquat.),
89.5 (Cquat.), 125.9 (CH), 127.2 (CH), 128.2 (CH), 146.8 (Cquat.). Ϫ
13C NMR (CD2Cl2, 100 MHz): δ ϭ 63.2 (Cquat.), 68.9 (CH), 69.6
(CH), 71.2 (CH), 74.1 (Cquat.), 85.6 (Cquat.), 86.8 (Cquat.), 125.1
(CH), 127.4 (CH), 128.1 (CH), 144.9 (Cquat.). Ϫ MS (70 eV, EI);
ent is considered to be sterically bulky.
Conclusion
Ferrocene stabilizes propargyl cations generated at the γ-
position to a large extent by delocalizing the positive charge
evenly over the iron center and the unsubstituted cyclo-
pentadienyl ring, as shown by NMR spectroscopy of the
cation 3. Therefore, the increasing contribution of the allen-
ylium canonical structures in three different organic/or-
ganometallic propargyl cations 4 can be detected by carbon
NMR spectroscopy and compared. For the ferrocenyl-sub-
stituted system a regioselectivity shift for the nucleophilic
attack of ethanol from the propargyl to the allenyl position
is the most significant difference between the phenyl and
(OC)3(Ph)Cr analogs. Thus, organometallic substituents
not only stabilize ambident electrophiles such as propargyl
cations but also could allow a fine tuning of the regioselec-
tivity of nucleophilic additions.
m/z (%): 392 [Mϩ] (61), 327 [Mϩ Ϫ C5H5] (13), 254 [Mϩ
Ϫ
CpFeOH] (31), 210 [MϩϪ Ph2CO] (100), 182 [Ph2COϩ] (52), 152
[Ph2COϩ Ϫ CH2O] (18), 105 [PhCOϩ] (70), 77 [Phϩ] (27), 56 [Feϩ]
(8). Ϫ IR (KBr): ν˜ ϭ 2230 cmϪ1, 1627, 1599, 1489, 1449, 1408,
1339, 1264, 1194, 1178, 1165, 1156, 1101, 1061, 1028, 998, 922,
903, 885, 843, 818, 772, 753, 715, 701, 641, 630, 594, 542, 519, 498,
488, 451, 415. Ϫ UV/Vis (DMSO): λmax (ε) ϭ 271 nm (8900), 445
(3200). Ϫ C25H20FeO (392.28): calcd. C 76.54, H 5.13; found C
76.51, H 5.22.
Preparation of the Propargyl Cation 3 for the NMR-Spectroscopic
Characterization: To a solution of 20 µL of tetrafluoroboric
acidϪdiethyl ether in 0.3 mL of CD2Cl2, placed in a nitrogen-
flushed NMR tube capped with a rubber septum, was added a
solution of 25 mg of 2 in 0.4 mL of CD2Cl2 at Ϫ78 °C. The NMR
tube with the dark green solution was then quickly transferred to
the NMR spectrometer (precooled to Ϫ70 °C).
Experimental Section
All reactions involving ferrocene complexes were carried out in
flame-dried Schlenk flasks under nitrogen by using septum and syr-
inge techniques. Solvents were dried and distilled according to
standard procedures.[18] Ϫ Column chromatography: Silica gel 60
(0.063Ϫ0.2 mm/70Ϫ230 mesh, Firma Merck Darmstadt). Ϫ TLC:
Silica gel plates (60 F254 Merck, Darmstadt). Ϫ Melting points
(uncorrected values): ReichertϪJung Thermovar. Ϫ Ethynylferro-
cene was synthesized according to a procedure of Rosenblum.[19]
All other reagents were purchased from Merck, Aldrich, or Fluka,
Generation of the Propargyl Cation 3 and Nucleophilic Trapping Re-
action (General Procedure): To a cooled solution (Ϫ78 °C) of 52
µL (0.32 mmol) of tetrafluoroboric acid (54% in diethyl ether) in
10 mL of dichloromethane was added dropwise a solution of
100 mg (0.25 mmol) of 2 in 5 mL of dichloromethane. After stirring
for 60 min, a solution of 1.0 mmol of the corresponding nucleoph-
ile in 5 mL of dichloromethane was added. The mixture was then
allowed to warm up to room temperature. After the addition of
10 mL of water, the solution was extracted with diethyl ether (9a:
dichloromethane) (3 ϫ 50 mL) and the combined organic phases
were dried with magnesium sulfate. Evaporation of the solvents
under reduced pressure furnished the products 9 (or 10), which
were recrystallized from diethyl ether/pentane or dichloromethane/
diethyl ether to give good to excellent yields.
1
and used without further purification. Ϫ H- and 13C-NMR spec-
tra: Bruker WM 300, Bruker AC 300, Bruker ARX 300 or Varian
VXR 400S; [D6]DMSO and [D2]dichloromethane.
Ϫ
IR:
PerkinϪElmer FT-IR spectrometer 1000 or PerkinϪElmer FT-IR
Paragon 1000 PC. The samples were pressed into KBr pellets and
the spectra recorded on NaCl plates. Ϫ UV/Vis: Beckman DK-
2a, Beckman UV 5240, or PerkinϪElmer model Lambda 16; J&
M TIDAS (transputer integrated diode array spectrometer) with a
Hellma low-temperature quartz probe (UV/Vis cation characteriza-
tion). Ϫ MS: Finnigan MAT 311-A/100MS, Finnigan MAT 90,
and MAT 95Q. Ϫ Elemental analyses were carried out in the Mic-
roanalytical Laboratories of the Institut für Organische Chemie,
Ludwig-Maximilians-Universität München.
1-Ferrocenyl-3,3-diphenyl-1-(triphenylphosphonium)propa-1,2-diene
Tetrafluoroborate (9a): According to the GP with 131 mg
(0.50 mmol) of triphenylphosphane to give 170 mg (95%) of 9a.
Red crystals, m.p. 216Ϫ218 °C (dichloromethane/diethyl ether). Ϫ
1H NMR (CD2Cl2, 300 MHz): δ ϭ 3.98 (s, 5 H), 4.15 (m, 2 H),
4.34 (m, 2 H), 7.04Ϫ7.88 (m, 25 H). Ϫ 13C NMR (CD2Cl2,
75 MHz): δ ϭ 70.2 (CH), 70.2 (CH), 70.4 (CH, JP,C ϭ 3.3 Hz),
86.7 (Cquat.), 93.7 (Cquat., JP,C ϭ 86.2 Hz), 116.9 (Cquat.), 118.1
(Cquat., JP,C ϭ 88.2 Hz), 128.4 (CH), 129.7 (CH), 129.9 (CH), 130.6
3-Ferrocenyl-1,1-diphenylprop-2-yne-1-ol (2): To a cooled solution
(Ϫ78 °C) of 1.00 g (4.90 mmol) of ethynylferrocene (1) in 40 mL of
THF was added dropwise 3.20 mL (5.10 mmol) of a 1.6  solution (CH, JP,C ϭ 12.6 Hz), 132.7 (Cquat.), 134.5 (CH, JP,C ϭ 9.9 Hz),
of butyllithium in hexanes over a period of 1 min. The reaction
mixture was stirred for a further 60 min. To this reaction mixture
136.0 (CH, JP,C ϭ 2.6 Hz), 216.8 (Cquat., JP,C ϭ 5.9 Hz). Ϫ MS
(FAB), m/z: 637 [Mϩ Ϫ BF4Ϫ], 375 [Mϩ Ϫ BF4 Ϫ PPh3]. Ϫ IR
Ϫ
Eur. J. Inorg. Chem. 2000, 2003Ϫ2009
2007

M. Ansorge, K. Polborn, T. J. J. Müller
FULL PAPER
(KBr): ν˜ ϭ 3435 cmϪ1, 3083, 3057, 1914, 1818, 1627, 1596, 1586,
sibility of using his J&M UV/Vis spectrometer. We cordially thank
1490, 1484, 1439, 1411, 1342, 1315, 1283, 1226, 1189, 1160, 1108, Dr. David S. Stephenson for recording the low-temperature NMR
1083, 1056, 998, 945, 923, 901, 825, 772, 754, 728, 717, 695, 626, spectra.
607, 574, 551, 533, 521, 497, 439. Ϫ UV/Vis (DMSO): λmax (ε) ϭ
275 nm (18490), 374 (1260), 470 (790). Ϫ [C43H34FePϩBF4
]
Ϫ
(724.36): calcd. C 71.30, H 4.73; found C 71.37, H 4.47.
[1]
[1a]
For reviews see, e.g.:
L. Haynes, R. Pettit, in: Carbonium
Ions (Eds.: G. A. Olah, P. v. R. Schleyer), Wiley, New York,
Methyl 3-Ferrocenyl-2,2-dimethyl-5,5-diphenylpenta-3,4-dienecarb-
oxylate (9b): According to the GP with 0.20 mL (1.0 mmol) of 1-
methoxy-2,2-dimethyl-1-trimethylsiloxyethene to give 108 mg
(93%) of 9b. Orange crystals, m.p. 132Ϫ133 °C. Crystals suitable
for X-ray structure analysis were obtained by slow crystallization
[1b]
1975, vol. 5. Ϫ
W. E. Watts, in: Comprehensive Organomet-
allic Chemistry (Eds.: G. Wilkinson, F. G. A. Stone, E. W.
Abel), Pergamon, Oxford, 1982, vol. 8, chapter 59, pp. 1051.
[1c]
[1d]
´
A. Solladie-Cavallo, Polyhedron 1985, 4, 901Ϫ928. Ϫ
[1e]
Ϫ
G. Jaouen, Pure Appl. Chem. 1986, 58, 597Ϫ616. Ϫ
K. M.
A. J. M.
[1f]
Nicholas, Acc. Chem. Res. 1987, 20, 207Ϫ214. Ϫ
from
a concentrated DMSO solution of 9b. Ϫ
1H NMR
Caffyn, K. M. Nicholas, in: Comprehensive Organometallic
Chemistry II (Eds.: E. W. Abel, F. G. A. Stone, G. Wilkinson),
Pergamon: Oxford, 1995, vol. 12, pp. 685Ϫ702.
([D6]DMSO, 300 MHz): δ ϭ 1.42 (s, 6 H), 3.63 (s, 3 H), 3.92 (s, 5
H), 4.22 (m, 4 H), 7.42Ϫ7.44 (m, 10 H). Ϫ 13C NMR ([D6]DMSO,
75 MHz): δ ϭ 26.1 (CH3), 45.5 (Cquat.), 52.4 (CH3), 67.4 (CH), 68.2
(CH), 69.3 (CH), 80.5 (Cquat.), 112.4 (Cquat.), 112.5 (Cquat.), 127.7
(CH), 128.0 (CH), 128.9 (CH), 136.2 (Cquat.), 176.3 (Cquat.), 204.7
(Cquat.). Ϫ MS (70 eV, EI); m/z (%): 476 [Mϩ] (100). Ϫ IR (KBr):
ν˜ ϭ 3430 cmϪ1, 3116, 3100, 3087, 3061, 2992, 2947, 1723, 1636,
1599, 1491, 1464, 1442, 1432, 1412, 1379, 1359, 1256, 1191, 1145,
1106, 1074, 1052, 1031, 1013, 1002, 973, 916, 867, 847, 823, 772,
762, 732, 695, 636, 624, 609, 601, 586, 505, 478. Ϫ UV/Vis
(DMSO): λmax (ε) ϭ 283 nm (15100), 458 (2800). Ϫ C30H28FeO2
(476.39): calcd. C 75.63, H 5.92; found C 75.84, H 6.07.
[2]
For selected applications of transition metal stabilized carben-
[2a]
ium ions for the synthesis of complex molecules see, e.g.:
S.
[2b]
G. Davies, T. J. Donohoe, Synlett 1993, 323Ϫ332. Ϫ
M.
Uemura, T. Kobayashi, Y. Hayashi, Synthesis 1986, 386Ϫ388.
[2c]
Ϫ
M. T. Reetz, M. Sauerwald, Tetrahedron Lett. 1983, 24,
[2d]
2837Ϫ2840. Ϫ
1996, 37, 4837Ϫ4840.
Modern Acetylene Chemistry (Eds.: P. J. Stang, F. Diederich),
E. J. Corey, C. J. Helal, Tetrahedron Lett.
[2e]
G. G. Melikyan, K. M. Nicholas, in:
[2f]
VCH, Weinheim, 1995, p. 118. Ϫ
K. C. Nicolaou, W. M.
Dai, Angew. Chem. 1991, 103, 1453Ϫ1481; Angew. Chem. Int.
Ed. Engl. 1991, 30, 1387. Ϫ [2g] P. Magnus, T. Pitterna, J. Chem.
[2h]
Soc., Chem. Commun. 1991, 541Ϫ543. Ϫ
P. Magnus, Tetra-
[2i]
hedron 1994, 50, 1397Ϫ1418. Ϫ
G. Wagner, R. Herrmann,
in: Ferrocenes (Eds.: A. Togni, T. Hayashi), VCH, Weinheim,
2-(1-Ferrocenyl-3,3-diphenylpropa-1,2-dienyl)cyclohexan-1-one (9c):
According to the GP with 0.19 mL (1.0 mmol) of 1-trimethylsiloxy-
cyclohexene to give 110 mg (93%) of 9c. Orange crystals, m.p.
1995, chapter 4. Ϫ [2j] A. J. Pearson, Iron Compounds in Organic
Synthesis, Academic Press, London, 1994.
[3]
[3a]
For semiempirical calculations see, e.g.:
D. W. Clack, L. A.
1
107Ϫ109 °C. Ϫ H NMR ([D6]DMSO, 300 MHz): δ ϭ 1.64Ϫ2.33
P. Kane-Maguire, J. Organomet. Chem. 1978, 145, 201Ϫ206. Ϫ
[3b] P. A. Downton, B. G. Sayer, M. J. McGlinchey, Organomet-
(m, 9 H), 4.08 (m, 5 H), 4.20Ϫ4.34 (m, 4 H), 7.26Ϫ7.46 (m, 10 H).
allics 1992, 11, 3281Ϫ3286; for recent computational studies
Ϫ
13C NMR ([D6]DMSO, 75 MHz): δ ϭ 24.2 (CH2), 27.6 (CH2),
[3c]
on the DFT level of theory see, e.g.:
A. Pfletschinger, T. K.
33.3 (CH2), 41.6 (CH2), 52.4 (CH), 66.1 (CH), 66.9 (CH), 68.6
(CH), 68.6 (CH), 69.1 (CH), 82.5 (Cquat.), 106.8 (Cquat.), 112.8
(Cquat.), 127.5 (CH), 127.6 (CH), 128.0 (CH), 128.0 (CH), 128.7
(CH), 128.8 (CH), 136.1 (Cquat.), 136.6 (Cquat.), 205.0 (Cquat.), 209.5
(Cquat.). Ϫ MS (70 eV, EI); m/z (%): 472 [Mϩ] (100). Ϫ IR (KBr):
ν˜ ϭ 3435 cmϪ1, 3080, 3054, 3022, 2934, 2860, 1706, 1630, 1597,
1491, 1447, 1411, 1380, 1349, 1336, 1310, 1296, 1246, 1197, 1156,
1126, 1105, 1072, 1060, 1028, 1001, 962, 920, 900, 874, 818, 769,
740, 696, 625, 608, 551, 505, 478, 452. Ϫ UV/Vis (DMSO): λmax
(ε) ϭ 281 nm (18320), 446 (4530). Ϫ C31H28FeO (472.40): calcd. C
78.81, H 5.97; found C 78.80, H 5.85.
Dargel, J. W. Bats, H.-G. Schmalz, W. Koch, Chem. Eur. J.
[3d]
1999, 5, 537Ϫ545. Ϫ
C. A. Merlic, J. C. Walsh, D. J. Tan-
tillo, K. N. Houk, J. Am. Chem. Soc. 1999, 121, 3596Ϫ3606.
[4]
For a recent monograph see, e.g.: Stable Carbocation Chemistry
(Eds.: G. K. Surya Prakash, P. v. R. Schleyer), John Wiley and
Sons, Inc., New York, 1997.
[5] [5a]
T. J. J. Müller, A. Netz, Organometallics 1998, 17,
[5b]
3609Ϫ3614. Ϫ
T. J. J. Müller, M. Ansorge, K. Polborn,
Organometallics 1999, 18, 3690Ϫ3701.
[6]
T. J. J. Müller, A. Netz, Tetrahedron Lett. 1999, 40, 3145Ϫ3148.
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M. Murray, Methoden Org. Chem. (Houben-Weyl) 1977,
vol. 5/2a, p. 991 (‘‘Methoden zur Herstellung und Umwand-
lung von Allenen bzw. Kumulenen’’). Ϫ [7b] H. Mayr, H. Klein,
[7c]
J. Org. Chem. 1981, 46, 4097Ϫ4100. Ϫ
J.-P. Dau-Schmidt,
1-Ferrocenyl-3,3-diphenylprop-2-en-1-one (10): According to the GP
with 100 mg (2.1) of ethanol to give 70 mg (70%) of 10. Red crys-
tals, m.p. 75Ϫ78 °C. Ϫ 1H NMR ([D6]DMSO, 300 MHz): δ ϭ 4.24
(s, 5 H), 4.56 (m, 2 H), 4.81 (m, 2 H), 7.08 (s, 1 H), 7.12Ϫ7.46 (m,
10 H). Ϫ 13C NMR ([D6]DMSO, 75 MHz): δ ϭ 69.6 (CH), 69.8
(CH), 72.5 (CH), 81.1 (Cquat.), 124.1 (CH), 127.7 (CH), 127.9 (CH),
128.3 (CH), 128.7 (CH), 129.2 (CH), 129.4 (CH), 139.5 (Cquat.),
141.3 (Cquat.), 151.0 (Cquat.), 193.4 (Cquat.). Ϫ MS (70 eV, EI), m/z
(%): 392 [Mϩ] (100). Ϫ IR (KBr): ν˜ ϭ 3435 cmϪ1, 3082, 2927,
1647, 1570, 1490, 1443, 1411, 1376, 1278, 1232, 1156, 1106, 1076,
1029, 1000, 892, 823, 788, 769, 725, 698, 582, 527, 500, 485. Ϫ UV/
Vis (DMSO): λmax (ε) ϭ 300 nm (12940), 377 (2400), 490 (14450).
Ϫ C25H20FeO (392.28): calcd. C 76.54, H 5.13; found C 76.67,
H 5.21.
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H. Mayr, Chem. Ber. 1994, 127, 205Ϫ212. Ϫ
S. M. Luky-
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V. I. Boev, A. V. Dombrovskii, J. Org.
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E. Bäuml,
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H.-O. Kalinowski, S. Berger, S. Braun, 13C NMR Spektrosko-
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Acknowledgments
The financial support of the Fonds der Chemischen Industrie, De-
utsche Forschungsgemeinschaft and the Dr.-Otto-Röhm-Gedächt-
nisstiftung is gratefully acknowledged. We wish to express our ap-
preciation to Prof. H. Mayr for his generous support and the pos-
Relative contribution of 4B ϭ [δ(Cγ or Cpara of 7) Ϫ δ(Cγ or
Cpara of 4)]/[δ(Cγ or Cpara of 7) Ϫ δ(Cγ or Cpara of 8)]ϫ100%.
Quantum CAChe 3.0 Program, Oxford Molecular Group, 1997.
T. Siegmund, Ph. D. Thesis, Universität München, 1999.
[14]
[15]
2008
Eur. J. Inorg. Chem. 2000, 2003Ϫ2009

The Ferrocenyldiphenylpropargyl Cation
FULL PAPER
[16]
The adduct of diisopropylamine and 3 was identified by NMR
obtained free of charge on application to CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK [Fax: (internat.) ϩ 44-1223/
336-033; E-mail: deposit@ccdc.cam.ac.uk].
Various editors, Organikum, 14th edition, VEB Deutscher Ver-
lag der Wissenschaften, Berlin, 1993.
spectroscopy to be the corresponding allyl cation. However, it
was not possible either to deprotonate this allyl cation with an
excess of amine base or to separate it from the ammonium salts
by fractional recrystallization.
[18]
[19]
[17]
Crystallographic data (excluding structure factors) for the
M. Rosenblum, N. Brown, J. Papenmeyer, M. Applebaum, J.
Organomet. Chem. 1966, 6, 173Ϫ180.
structure reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC-142337 (9b). Copies of the data can be
Received March 24, 2000
[I00115]
Eur. J. Inorg. Chem. 2000, 2003Ϫ2009
2009