The deviating behavior of thiols in nucleophilic trapping reactions of chromiumcarbonyl phenyl complex substituted propargyl cation

Article abstract of DOI:10.1016/S0022-328X(01)01162-7

The (phenyl)Cr(CO)₃-complex substituted propargyl cation 4 significantly deviates in the chemoselectivity of the nucleophilic attack of thiols from the previously reported planar chiral ortho-substituted arene complexes and furnishes allenyl thioethers 5. This peculiar behavior can be rationalized assuming a subsequent base catalyzed propargyl-allenyl isomerization in acidic medium (!). An X-ray structure analysis of allenyl thioether 5c recrystallized from acetonitrile over weeks reveals that the [2+2] cyclodimer 10 has been formed. Thiolate adds to 5c to give a single diastereomer of the allyl compound 15 in good yield.

Full text of DOI:10.1016/S0022-328X(01)01162-7

Journal of Organometallic Chemistry 640 (2001) 41–49
www.elsevier.com/locate/jorganchem
The deviating behavior of thiols in nucleophilic trapping reactions
of chromiumcarbonyl phenyl complex substituted propargyl cation
Astrid Netz, Kurt Polborn, Thomas J.J. Mu¨ller *
Department Chemie der Ludwig-Maximilians, Uni6ersita¨t Mu¨nchen, Butenandt-Str. 5-13 (Haus F), D-81377 Mu¨nchen, Germany
Received 3 May 2001; accepted 5 July 2001
Abstract
The (phenyl)Cr(CO)3-complex substituted propargyl cation 4 significantly deviates in the chemoselectivity of the nucleophilic
attack of thiols from the previously reported planar chiral ortho-substituted arene complexes and furnishes allenyl thioethers 5.
This peculiar behavior can be rationalized assuming a subsequent base catalyzed propargyl–allenyl isomerization in acidic
medium (!). An X-ray structure analysis of allenyl thioether 5c recrystallized from acetonitrile over weeks reveals that the [2+2]
cyclodimer 10 has been formed. Thiolate adds to 5c to give a single diastereomer of the allyl compound 15 in good yield. © 2001
Elsevier Science B.V. All rights reserved.
Keywords: Allenylation; Arene complexes; Chromium; Cycloaddition; Isomerization
1. Introduction
upon bending towards the metal center [2d,2e] [4]. Since
ionizations of propargyl precursors form ambident
propargyl cations [5] that can be interesting intermedi-
ates for more sophisticated arene sidechain functional-
izations via aryl propargyl or allenyl derivatives, we
have initiated a program to investigate (arene)Cr(CO)3-
complexes bearing p-substituents, [6] particularly
propargyl cations [7]. In kinetic studies we could deter-
mine the electrophilic reactivity of a (arene)Cr(CO)3-
The advent of transition metal p-complex stabilized
a-carbenium ions [1] has revolutionized the synthetic
application of often elusive reactive carbocation inter-
mediates, in particular, in stereoselective nucleophilic
additions with retention of configuration. Among tran-
sition metal p-complex stabilized carbenium ions the
most prominent representatives are ferrocenyl-,
(alkyne)Co2(CO)6-, or (arene)Cr(CO)3-substituted car-
bocations [1]. A pronounced neighboring group effect
arising from an ideal overlap of occupied d-orbitals on
the metal and the vacant p-orbital at the carbenium
center in a-position also rationalizes the conservation of
the stereochemical information at the previous sp3-cen-
ter as a consequence of an overall retention of configu-
ration due to a double inversion mechanism [1c,1d,1f].
In particular, chromiumcarbonyl complexed benzylic
cations [2] have found applications in asymmetric or-
ganic syntheses [1f] [3]. According to calculations at
different levels of theory for chromium carbonyl com-
plexed benzyl cations the carbenium center is signifi-
cantly distorted from coplanarity with the phenyl ring
complex substituted propargyl cation
1
(R1=H;
R2=Ph) revealing that this system is by two orders of
magnitude more reactive than the comparable
Nicholas’ cation 2 (R1, R3=H; R2=Ph) [8] (Plate 1).
Recently, we have reported the regio- and
diastereoselective addition of nucleophiles to planar
chiral complex substituted a-propargyl cations furnish-
ing propargyl derivatives [9]. Most interestingly, the
chemoselectivity of the trapping reaction of thiols to
the parent system 1 (R1=H, R2=Ph) deviates signifi-
cantly from the ortho-substituted cases and leads to the
formation of allenyl thioethers [10]. Now, in the light of
nucleophilic addition-isomerization sequences [11], we
wish to elucidate this peculiar allene formation and
disclose a representative [2+2]-cycloaddition as well as
a nucleophilic addition to these novel organometallic
allenes.
* Corresponding author. Tel.: +49-89-2180-7714; fax: +49-89-
2180-7717.
E-mail address: tom@cup.uni-muenchen.de (T.J.J. Mu¨ller).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01162-7

42
A. Netz et al. / Journal of Organometallic Chemistry 640 (2001) 41–49
Plate 1.
2. Results and discussion
the stabilization of an adjacent anion. Thus, upon
rotation of 7 an anti-periplanar alignment of the
propargyl proton and the electron withdrawing chromi-
umcarbonyl tripod enhances the kinetic acidity of this
propargyl proton now being stereoelectronically acti-
vated by two electron withdrawing substituents, the
arene complex fragment and the sulfonium yield moi-
ety. As a consequence, the deprotonation with any
weakly basic molecule furnishes the reasonably stabi-
lized propargyl anion 8 that is subsequently protonated
to give after decoordination of the activating Lewis acid
the thermodynamically more stable allene derivative 5.
Hence, the question arises why this peculiar isomer-
ization does not proceed in the case of ortho-substituted
According to our general protocol the ionization of
the racemic (phenyl)Cr(CO)3-complex substituted
propargyl acetate 3 furnishes quantitatively the propar-
gyl cation 4 (i.e. 1 with R1=H, R2=Ph) at −78 °C in
dichloromethane [7a]. The addition of a slight excess of
the trapping thiols now gives rise to the formation of
the allene derivatives 5 as racemic mixtures in good
yields (Scheme 1).
Neither the ester functionality (5b) nor the aromatic
substituent (5c) interfere with the chemoselectivity of
this allenylation reaction. Characteristically, the central
allenyl carbon resonances in the 13C-NMR spectra of
the allenes 5 appear between l 202 and 208 [12]. Most
interestingly, the nucleophilic attack of the thiols has
obviously occurred at the a-position as shown by
1
NOESY and selectively H-decoupled 13C-NMR spec-
tra indicating a close spatial proximity of the allene
proton and the ortho-protons on the terminal phenyl
substituent (Scheme 2).
Interestingly, in all mass spectra of the allene deriva-
tives 5 an intense fragment at m/z=191 can be de-
tected. This stable intermediate can be assigned to the
1,3-diphenyl propargyl cation, i.e. the hydrocarbon lig-
and of 4.
Mechanistically, this process can be regarded as a
nucleophilic addition-isomerization sequence and is re-
lated to our recent findings on the trapping reactions
with triphenylphosphane [11]. Therefore, the following
mechanistic scenario can be plausibly rationalized. The
nucleophilic attack of the thiol occurs at the a-position
to give the propargylated intermediate 6 (Scheme 3) in
agreement with the findings from the diastereoselective
propargylation studies with planar chiral complex sub-
stituted propargyl cations. Thioethers, however, are
sufficiently Lewis basic so that a Lewis acid–base ad-
duct 7 can be easily formed. As in the case of the
phosphane adducts a subsequent isomerization can pro-
ceed through a propargyl anion [13] in the sense of a
base catalyzed propargyl–allenyl isomerization if the
chromiumcarbonyl complexed arene substituent can
efficiently exert its amphoteric nature, i.e. in this case
Scheme 1.
Scheme 2. Selected nOe contacts (dotted line: weak contact) in the
spectrum of 5c

A. Netz et al. / Journal of Organometallic Chemistry 640 (2001) 41–49
43
Scheme 3.
aryl complexed propargyl cations [9]. According to the
postulated mechanistic rationale the crucial anti-
periplanar conformation necessary for a kinetically con-
trolled deprotonation can only be populated through
an unhindered rotation of the Lewis acid–base adduct
7. However, in the case of thiol adducts to ortho-substi-
tuted aryl complexed propargyl cations the rotation
around the CipsoꢀCa bond in the resulting adduct 9 is
massively hampered and, thus, the base-catalyzed sub-
sequent isomerization is not feasible (Plate 2).
It is noteworthy to mention that out of eight racemic
diastereomers only those four with a s-anti configura-
tion of the non-complexed phenyl ring at the double
bond can be realized assuming minimal steric interac-
In crystallization attempts from various solvents and
solvent mixtures in order to grow suitable crystals for
an X-ray structure analysis of the organometallic al-
lenes 5 we observed that compound 5c only slowly
forms red plates in acetonitrile as a solvent (recrystal-
lization from diethylether or dichloromethane only
gives yellow crystals of 5c in poor quality) [14]. Most
interestingly, the X-ray structure analysis of presumed
compound 5c (Fig. 1, Table 1) showed clearly that after
several weeks a dimerization and crystallization at low
temperatures (+4 °C refrigerator temperature) had
taken place (Scheme 4).
Plate 2.
A closer inspection of the bond distances and angles
as well as the stereochemistry identifies compound 10 as
a 1,2-bis(methylidene)cyclobutane derivative as a result
of a [2+2]-cycloaddition of two molecules of 5c with
the same configuration. Most surprisingly, the bis(-
methylidene)cyclobutane 10 is formed as a racemic
mixture of a single diastereomer (out of eight possible
racemic pairs of diastereomers) indicating a highly
stereoselective cycloaddition. This reaction is addition-
ally favored in a dipolar aprotic solvent and can be
attributed to a more or less polar transition state.
Assuming a concerted [2+2]-cycloaddition the transi-
tion state leading to the formation of 10 is best de-
scribed by a mutually orthogonal arrangement of an
internal allene double bond of the first molecule and a
terminal allene double bond of its reaction partner
(Scheme 5).
,
Fig. 1. ORTEP plot of 10. Selected bond lengths [A], angles [°] and
dihedral angles [°]: C(34)-C(18): 1.589, C(18)ꢀC(17): 1.507,
C(17)ꢀC(41): 1.454, C(34)ꢀC(41): 1.542, C(17)ꢀC(10): 1.341,
C(41)ꢀC(42): 1.336, C(17)ꢀC(18)ꢀC(34): 87.49, C(18)ꢀC(34)ꢀC(41):
87.00, C(18)ꢀC(17)ꢀC(41): 93.42, C(18)ꢀC(34)ꢀC(41)ꢀC(42): 166.50,
C(10)ꢀC(17)ꢀC(41)ꢀC(42): 16.75.

44
A. Netz et al. / Journal of Organometallic Chemistry 640 (2001) 41–49
Table 1
Crystal data and structure refinements for 10
10
Empirical formula
Formula weight
Temperature (K)
C48H30Cl2Cr2O6S2
941.74
293(2)
,
Radiation (A)
0.71073
Anorthic
Crystal system
Space group
(
P 1
Unit cell dimensions
,
a (A)
12.154(3)
12.414(5)
15.635(7)
84.37(3)
72.79(3)
76.21(3)
2187.5(14)
2
1.430
8-scans
0.763
Scheme 5.
,
b (A)
,
c (A)
cycloaddition only structure 10 can be formed under
the observed conditions.
a (°)
b (°)
g (°)
Since allenes are an interesting class of unsaturated
compounds in the field of preparative chemistry [16] we
are intrigued to study nucleophilic additions at
organometallic allenes like 5 [17]. Upon addition of
allene 5c to a solution of sodium isopropyl thiolate a
color change from yellow to orange indicates the for-
mation of an intermediate with extended p-conjugation
presumably the allyl anion 14 (Scheme 7). Aqueous
workup of this solution furnishes the allyl derivative 15
as yellow needles in 78% yield as a single diastereomer.
According to NOESY and HETCOR-NMR spectra
of 15 the h-allyl proton adjacent to the phenyl chromi-
umcarbonyl and the aryl thioether unambiguously es-
tablishes the regiochemistry of the protonation of the
allyl anion 14 and the Z-configuration of the double
bond can be readily assigned by several diagnostic nOe
(nuclear Overhauser effect) contacts (Scheme 8).
The terminating and highly regioselective protona-
tion of the allyl anion is in agreement with the principle
of allopolarization [18] where the electrophilic attack at
a-acceptor substituted allyl anions preferentially occurs
at the a-position, thus, furnishing a non-conjugated
regioisomer. However, the highly stereoselective forma-
tion of the trisubstituted double bond with Z-configu-
ration is accomplished in the nucleophilic addition step
to 5c in the sequence. According to calculations on the
extended Hu¨ckel level of theory [15] the energy differ-
ence between the Z-configured isomer 15 and the E-
configured diastereomer 19 is too small to explain the
pronounced stereoselectivity (Scheme 9). Thus, each
3
,
Volume (A )
Z
Dcalc (g/cm−3
)
Absorption correction
Absorption coefficient (mm−1
Max/min transmission
F(000)
Crystal size (mm)
q range (min/max) (°)
Index ranges
)
–
960
0.40×0.40×0.27
2.73–23.98
−135h513
−145k514
−05l517
7116
6829 [R(int)=0.0145]
6829 [I\2|(I)]
SHELXL-93 on F2
6829/2/561
1.086
Reflections collected
Independent reflections
Reflections observed
Refinement method
Data/restraints/parameters
Goodness of fit on F2
Final R indices [I\2|(I)]
R1
0.0504
0.1090
wR2
R indices (all data)
R1
0.0790
0.1249
0.455 and −0.326
wR2
−3
,
Largest difference peak and hole (e A
)
tions in the transition state and in the product (Scheme
6). Considering the relative heats of formation accord-
ing to calculations on the diastereomeric structures 10
to 13 on the extended Hu¨ckel level of theory [15] and
assuming a late polar transition state for the [2+2]
Scheme 4.

A. Netz et al. / Journal of Organometallic Chemistry 640 (2001) 41–49
45
Scheme 6. Extended Hu¨ckel calculations on the four most probable cycloadduct diastereomers.
Scheme 7.
allyl product can be derived from two corresponding
allyl anions. The inspection of the stereochemical corre-
lation shows that the observed product 15 is formed by
protonation of either allyl anion 14 or 16. In turn, the
hypothetical E-isomer is deduced from the protonation
of the allyl anions 17 and 18. The extended Hu¨ckel
calculations [15] on the four diastereomeric allyl anions
14, 16, 17, and 18 reveal that the most stable allyl anion
in this series is 14. Therefore, the stereochemical out-
come of this addition-protonation sequence is deter-
mined by its stereochemistry in the initial nucleophilic
addition of the thiolate to the allene giving rise to the
highly stereoselective generation of the allyl anion 14.
Finally, the regioselective protonation at the a-position
is achieved and concludes this sequence.
cation furnishing allenes instead of propargyl deriva-
tives. This peculiar sequence is related to previously
reported addition-isomerization sequences of phos-
phanes and is caused by the synergism of an anion-sta-
bilizing substituent and the amphoteric (phenyl)-
chromiumcarbonyl fragment [11]. Two representative
reactions, i.e. a thermal [2+2]-cycloaddition at low
temperature in a polar solvent and a nucleophilic thio-
late addition have shown that these organometallic
3. Conclusion
In conclusion we have explained the deviating behav-
ior of thiols in the nucleophilic trapping reactions with
the (phenyl)chromiumcarbonyl-substituted propargyl
Scheme 8. Selected nOe contacts (dotted line: weak contact) in the
spectrum of 15.

46
A. Netz et al. / Journal of Organometallic Chemistry 640 (2001) 41–49
Scheme 9. Extended Hu¨ckel calculations on the four allyl anion diastereomers 14, 16, 17, and 18 (relative energies) and the two allyl derivatives
15 and 19 (relative energies).
stadt). (b) TLC: silica gel plates (60 F254 Merck, Darm-
stadt); (c) Melting points (uncorrected values):
Reichert–Jung Thermovar. (d) The propargyl acetate
complex 3 was prepared according to our published
procedure [7a]. The thiols were purchased from Merck,
Aldrich or Fluka, and used without further purifica-
allenes behave largely like related organic compounds.
Most significantly, the (phenyl)chromiumcarbonyl frag-
ment exerts its electron withdrawing nature and its
steric bulk giving rise to highly regio- and stereoselec-
tive allylations. Further studies with these organometal-
lic allenes will be directed towards heterocycle syntheses
on a metal template.
1
tion. (e) H-and 13C-NMR spectra: Bruker WM 300,
Bruker AC 300, Bruker ARX 300 or Varian VXR 400S
DMSO-d6. (f) IR: Perkin-Elmer FT-IR spectrometer
1000 or Perkin-Elmer FT-IR Paragon 1000 PC. The
samples were pressed into KBr pellets or recorded on
NaCl plates, (g) UV–Vis: Beckman DK-2-a or Beck-
man UV 5240. (h) MS: Finnigan MAT 311-A/100MS,
Finnigan MAT 90 and MAT 95 Q; (i) Elemental analy-
sis were carried out in the Microanalytical Laboratories
of the Department Chemie, Ludwig–Maximilians-Uni-
versita¨t Mu¨nchen.
4. Experimental
All reactions involving tricarbonylchromium com-
plexes were carried out in flame-dried Schlenk flasks
under nitrogen by using septum and syringe techniques.
Solvents were dried and distilled according to standard
procedures [19]. (a) Column chromatography: silica gel
60 (0.063–0.2 mm/70–230 mesh, Firma Merck Darm-

A. Netz et al. / Journal of Organometallic Chemistry 640 (2001) 41–49
47
4.1. Generation of the cation 4 and nucleophilic
trapping reactions (General Procedure, GP).
2.92 (m, 2 H), 3.52 (s, 3 H), 5.74–5.78 (m, 2 H), 5.81
(m, 1 H), 5.87 (m, 2 H), 7.15 (s, 1 H), 7.33–7.40 (m, 5
H).-13C-NMR (DMSO-d6, 75 MHz): l 28.0 (CH2), 33.6
(CH2), 51.8 (CH3), 93.1 (CH), 93.2 (CH), 94.5 (CH),
94.6 (CH), 94.7 (CH), 103.2 (CH), 104.7 (Cquat.), 105.0
(Cquat.), 127.6 (CH), 128.8 (CH), 129.3 (CH), 132.5
(Cquat.), 171.1 (Cquat.), 202.3 (Cquat.), 233.7 (Cquat., CO).
MS (EI, 70 eV), m/z (%): 446 (M+, 2), 362 (M+−3
CO, 51), 310 (M+-Cr(CO)3, 1), 244 (C15H12Cr+, 70),
243 (C15H11Cr+, 12), 191 (C6H5CHCCC6H+5 , 100), 52
(Cr+, 25). IR (KBr): =1965 cm−1, 1887, 1732. UV–
Vis (Me2SO): lmax(o)=318 nm (9400). Anal. Calcd. for
C22H18CrO5S (446.4): C, 59.19; H, 4.06; S 7.18. Found:
C, 59.45; H, 4.17; S, 7.01.
To a solution of the acetate 3 in 18 ml of
dichloromethane, cooled to −78 °C, were added drop-
wise 1.4 equivalents of boron trifluoride etherate. The
purple red solution was stirred at −78 °C for 50 min
and then the corresponding thiol was added dropwise
in substance or dissolved in dichloromethane to the
solution of the cation. The color of the solution turns
from purple red to yellow and the reaction mixture was
stirred at the times indicated. Then 20 ml of diethyl
ether and 20 ml of water were added successively to the
reaction mixture which was subsequently allowed to
come to room temperature after several extractions
with diethyl ether the combined organic phases were
dried over magnesium sulfate. The solvents were evapo-
rated in vacuo and the residue was either recrystallized
from diethyl ether/pentane or purified by flash chro-
matography to give pure allenyl derivatives 5.
4.1.3. Cr(CO)3(p6-C6H5)C(S-p-C6H4Cl).C.CHC6H5
(5c)
According to the GP 100 mg (0.26 mmol) of 3 were
ionized and allowed to react for 90 min with 85 mg
(0.59 mmol) of p-chloro thiophenol. After workup the
crude product was purified by crystallization from di-
ethyl ether/pentane to give 98 mg (80%) of pure 3c as
4.1.1. Cr(CO)3(p6-C6H5)C[SCH(CH3)2].C.CHC6H5
(5a)
1
yellow crystals. Mp: 85 °C. H-NMR ([D6]Me2SO, 300
According to the GP 150 mg (0.39 mmol) of 3 were
ionized and allowed to react for 30 min with 0.08 ml
(0.85 mmol) of 2-propanethiol. After workup the crude
product was purified by flash chromatography on silica
gel (diethyl ether/pentane 1:2) and recrystallization
from pentane to give 112 mg (72%) of pure 5a as a
MHz): l 5.72–5.78 (m, 3 H), 5.92 (m, 2 H), 7.08 (s, 1
H), 7.34–7.39 (m, 7 H), 7.49 (d, J=8.4 Hz, 2 H).
13C-NMR (DMSO-d6, 75 MHz): l 93.3 (CH), 94.5
(CH), 94.6 (CH), 100.5 (CH), 102.6 (Cquat.), 104.2
(Cquat.), 127.7 (CH), 128.8 (CH), 129.2 (CH), 129.5
(CH), 131.4 (Cquat.), 132.1 (CH), 132.5 (Cquat.), 132.6
(Cquat.), 208.1 (Cquat.), 233.6 (Cquat., CO). MS (EI, 70
eV), m/z (%): 472/470 (M+, 4/10), 388/386 (M+−3
CO, 44/100), 336/334 (M+−Cr(CO)3, 2/5), 244
(C15H12Cr+, 28), 243 (C15H11Cr+, 17), 191
(C6H5CHCCC6H+5 , 93), 52 (Cr+, 43).-IR (KBr): =
1966 cm−1, 1883.-UV–Vis (Me2SO): lmax(o)=320 nm
(11200). Anal. Calcd. for C24H15ClCrO3S (470.9): C,
61.22; H, 3.21; Cl, 7.53; S, 6.81. Found: C, 61.45; H,
3.24; Cl, 7.22; S, 6.86.
1
yellow powder. Mp: 97–98 °C. H-NMR ([D6]Me2SO,
400 MHz): l 1.27 (d, J=6.8 Hz, 3 H), 1.30 (d, J=6.6
Hz, 3 H), 3.15 (m, 1 H), 5.72–5.79 (m, 3 H), 5.86 (d,
J=6.2 Hz, 1 H), 5.92 (d, J=6.3 Hz, 1 H), 7.09 (s, 1
H), 7.30 (t, J=6.9 Hz, 1 H), 7.36–7.43 (m, 4 H).
13C-NMR ([D6]Me2SO, 100 MHz): l 22.90 (CH3),
23.12 (CH3), 37.92 (CH), 93.21 (CH), 94.34 (CH), 94.42
(CH), 94.65 (CH), 101.17 (CH), 103.65 (Cquat.), 105.44
(Cquat.), 127.56 (CH), 128.50 (CH), 129.16 (CH), 132.37
(Cquat.), 204.61 (Cquat.), 233.66 (Cquat., CO).-MS (EI, 70
eV), m/z (%): 402 (M+, 4), 346 (M+−2 CO, 12), 318
(M+−3 CO, 44), 244 (C15H12Cr+, 100), 243
(C15H11Cr+, 6), 191 (C6H5CHCCC6H+5 , 50), 52 (Cr+,
22). IR (KBr): =1964 cm−1, 1901, 1875. UV–Vis
(Me2SO): lmax (o)=319 nm (10300). Anal. Calcd. for
C21H18CrO3S (402.4): C, 62.69; H, 4.51; S, 7.97. Found:
C, 62.85; H, 4.76; S, 8.05.
4.2. Cr(CO)3(p6-C6H5)CH(S-p-C6H4Cl)C[SCH-
(CH3)2].CHC6H5 (15)
To a suspension of 14 mg (0.54 mmol) of NaH in 10
ml of THF under nitrogen was added dropwise 50 ml
(0.53 mmol) of 2-propanethiol and the mixture was
stirred for 35 min until the evolution of hydrogen had
ceased. Then a solution of 100 mg (0.21 mmol) of the
allene 5c in 5 ml of THF were added to the cooled
suspension (−9 °C) and the reaction mixture was
stirred for 45 min at −9 °C before 10 ml of a satu-
rated aqueous solution of sodium bicarbonate were
added. The aqueous layer was extracted twice with
diethylether (2×30 ml). After drying with magnesium
sulfate and evaporation of the solvents in vacuo the
residue crystallized from diethylether–pentane (1:1) to
furnish 91 mg (78%) of 15 as yellow needles. Mp.
4.1.2. Cr(CO)3(p6-C6H5)C(SCH2CH3CO2CH3).
C.CHC6H5 (5b)
According to the GP 150 mg (0.39 mmol) of 3 were
ionized and allowed to react for 50 min with 0.11 ml
(0.85 mmol) of methyl 3-mercapto propionate. After
workup the crude product was purified by flash chro-
matography on silica gel (diethyl ether–pentane 1:5-
1:1) to give 129 mg (74%) of pure 5b as a yellow
oil.-1H-NMR ([D6]Me2SO, 300 MHz): l 2.64 (m, 2 H),

48
A. Netz et al. / Journal of Organometallic Chemistry 640 (2001) 41–49
121 °C.-1H-NMR (DMSO-d6, 400 MHz): l 0.70 (d,
J=5.4 Hz, 3 H), 0.81 (d, J=5.5 Hz, 3 H), 2.73 (m, 1
H), 5.09 (s, 1 H), 5.63–5.68 (m, 2 H), 5.76 (m, 1 H),
5.96 (d, J=5.1 Hz, 1 H), 6.01 (d, J=5.1 Hz, 1 H), 7.23
(m, 2 H), 7.31 (m, 2 H), 7.42 (d, J=7.3 Hz, 2 H), 7.51
(m, 2 H), 7.58 (d, J=7.2 Hz, 2 H). 13C-NMR (DMSO-
d6, 100 MHz): l 22.60 (CH3), 22.72 (CH3), 36.18 (CH),
60.12 (CH), 92.41 (CH), 92.66 (CH), 95.69 (CH), 96.18
(CH), 96.80 (CH), 110.59 (Cquat.), 127.95 (CH), 128.31
(CH), 128.91 (CH), 129.19 (CH), 132.41 (Cquat.), 133.19
(Cquat.), 134.28 (Cquat.), 135.05 (CH), 135.49 (CH),
135.87 (Cquat.), 233.65 (Cquat., CO).-MS (70 eV, EI), m/z
(%): 548/546 (M+, 0.4/0.9), 520/518 (M+−CO, 1/2),
492/490 (M+−2 CO, 12/23), 464/462 (M+−3 CO,
50/100), 388/368 (M+−3 CO,ꢀHSCH(CH3)2; 20/43),
320 (M+−3 CO,ꢀHSC6H4Cl; 65), 278 (M+−3
CO,ꢀHSC6H4Cl,ꢀCH2.CHCH3; 65), 267 (M+−
Cr(CO)3,ꢀSC6H4Cl; 48), 192 (M+−Cr(CO)3,ꢀSC6-
H4Cl,ꢀSCH(CH3)2; 73), 191 (M+−Cr(CO)3,ꢀSC6H4-
(e) K.M. Nicholas, Acc. Chem. Res. 20 (1987) 207. For stabiliza-
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(f) S.G. Davies, T.J. Donohoe, Synlett (1993) 323.
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Cl,ꢀHSCH(CH3)2; 91). IR (KBr): 1989 cm−1
1969, 1876, 1475, 1094, 1013, 660, 630, 534. UV–Vis
,
[4] (a) For recent computational studies on the DFT level of theory,
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(Me2SO): lmax(o) 318 nm (14900). Anal. Calcd. for
C27H23ClCrO3S2 (547.06): C, 59.28; H, 4.24; Cl, 6.48; S,
11.72. Found: C, 59.34; H, 4.31; Cl, 6.34; S, 11.40.
[5] (a) M. Murray, in: Methoden zur Herstellung und Umwandlung
von Allenen bzw. Kumulenen (Eds.), Houben-Weyl, Georg
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(b) T.J.J. Mu¨ller, Tetrahedron Lett. 38 (1997) 1025;
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578 (1999) 252;
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 160434 for compound 10.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
(d) M. Ansorge, T.J.J. Mu¨ller, J. Organomet. Chem. 585 (1999)
174;
(e) T.J.J. Mu¨ller, J. Organomet. Chem. 578 (1999) 95;
(f) T.J.J. Mu¨ller, A. Netz, M. Ansorge, E. Schma¨lzlin, C.
Bra¨uchle, K. Meerholz, Organometallics 18 (1999) 5066.
[7] (a) T.J.J. Mu¨ller, A. Netz, Organometallics 17 (1998) 3609;
(b) T.J.J. Mu¨ller, M. Ansorge, K. Polborn, Organometallics 18
(1999) 3690;
Acknowledgements
(c) A. Netz, T.J.J. Mu¨ller, Organometallics 19 (2000) 1452;
(d) M. Ansorge, K. Polborn, T.J.J. Mu¨ller, Eur. J. Inorg, Chem.
(2000) 2003.
The financial support of the Fonds der Chemischen
Industrie (Ph.D. scholarship for A.N.) and the
Deutsche Forschungsgemeinschaft is gratefully ac-
knowledged. We wish to express our appreciation to
Professor H. Mayr for his generous support.
[8] A. Netz, T.J.J. Mu¨ller, Tetrahedron 56 (2000) 4149.
[9] (a) T.J.J. Mu¨ller, A. Netz, Tetrahedron Lett. 40 (1999) 3145;
(b) A. Netz, K. Polborn, T.J.J. Mu¨ller, J. Am. Chem. Soc. 123
(2001) 3441.
[10] This aspect has initially been misinterpreted in [7a].
[11] A. Netz, T.J.J. Mu¨ller, Organometallics 20 (2001) 376.
[12] H.-O. Kalinowski, S. Berger, S. Braun, 13C-NMR Spek-
troskopie, Georg Thieme Verlag, Stuttgart, New York, 1984, p.
273.
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