Synthesis of chiral β-aminoalcohol-substituted carbene complexes of manganese and influence of the chiral carbene ligand on the diastereoselectivity of the CO/PR3 exchange

Article abstract of DOI:10.1016/S0022-328X(00)00753-1

The acetoxy(phenyl)carbene complex [Cp(CO)₂Mn=C(OAc)Ph] (2) reacts with chiral β-aminoalcohols HOR^* [HOR^* = N,N-dimethyl alaninol (3), N,N-dimethyl valinol (4), N,N-dimethyl leucinol (5), N,N-dimethylphenyl alaninol (6), and N-formylprolinol (7)] by displacement of the acetoxy substituent and formation of the β-aminoalkoxy(phenyl)carbene complexes [Cp(CO)₂Mn=C(OR^*)Ph] (8-12). Irradiation of 9-12 in the presence of PR₃ (R = Ph, OMe) affords the carbene(carbonyl)cyclopentadienyl(PR₃)manganese complexes [Cp(CO)(PR₃)Mn=C(OR^*)Ph]. The substitution proceeds diastereoselectively, the diastereomeric excess ranging from 28% to > 90%. The highest diastereoselectivity (> 90%) is observed in the reaction of 9 (R^* = CH₂C(NMe₂)HCMe₂H) with PR₃. In solution, complex 9 is not stable configurationally and epimerizes within a few days. The reaction of 2 with HOC₂H₄SCH₂Ph affords [Cp(CO)₂Mn=C(OC₂H₄SCH₂Ph)Ph] (22) which, on photolysis, is transformed, by loss of a CO ligand, into a chelating carbene complex (24). In the presence of PR₃ compound 24 cannot be converted thermally into [Cp(CO)(PR₃)Mn=C(OC₂H₄SCH₂Ph)Ph].

Full text of DOI:10.1016/S0022-328X(00)00753-1

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 621 (2001) 344–351
Synthesis of chiral b-aminoalcohol-substituted carbene complexes
of manganese and influence of the chiral carbene ligand on the
diastereoselectivity of the CO/PR3 exchange
Kerstin Weißenbach, Helmut Fischer *
Fachbereich Chemie, Uni6ersita¨t Konstanz, Fach M727, D-78457 Konstanz, Germany
Received 25 August 2000; accepted 13 September 2000
Dedicated to Professor Henri Brunner on the occasion of his 65th birthday
Abstract
The acetoxy(phenyl)carbene complex [Cp(CO)2MnꢀC(OAc)Ph] (2) reacts with chiral b-aminoalcohols HOR* [HOR*=N,N-
dimethyl alaninol (3), N,N-dimethyl valinol (4), N,N-dimethyl leucinol (5), N,N-dimethylphenyl alaninol (6), and N-formylproli-
nol (7)] by displacement of the acetoxy substituent and formation of the b-aminoalkoxy(phenyl)carbene complexes
[Cp(CO)2MnꢀC(OR*)Ph] (8–12). Irradiation of 9–12 in the presence of PR3 (R=Ph, OMe) affords the carbene(car-
bonyl)cyclopentadienyl(PR3)manganese complexes [Cp(CO)(PR3)MnꢀC(OR*)Ph]. The substitution proceeds diastereoselectively,
the diastereomeric excess ranging from 28% to \90%. The highest diastereoselectivity (\90%) is observed in the reaction of 9
(R*=CH2C(NMe2)HCMe2H) with PR3. In solution, complex 9 is not stable configurationally and epimerizes within a few days.
The reaction of 2 with HOC2H4SCH2Ph affords [Cp(CO)2MnꢀC(OC2H4SCH2Ph)Ph] (22) which, on photolysis, is transformed, by
loss of a CO ligand, into a chelating carbene complex (24). In the presence of PR3 compound 24 cannot be converted thermally
into [Cp(CO)(PR3)MnꢀC(OC2H4SCH2Ph)Ph]. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Carbene complexes; Substitution; Diastereoselectivity; Chiral complexes
1. Introduction
The synthesis involved addition of carbohydrates to
isocyanide complexes of Au and Pt. Later on, addi-
tional routes were developed such as Michael-addition
to a,b-unsaturated carbene complexes [4], addition of
carbonylmetallates to carbohydrate acid chlorides [5],
or addition of monodeprotonated protected carbohy-
drates to the carbyne carbon atom in cationic carbyne
complexes [6].
Recently we reported on the synthesis of a series of
chiral carbohydratocarbene complexes of the type
[Cp(CO)2MꢀC(OR*)R%] (M=Mn, Re; OR*=gluco-
and galactopyranosyloxy and glycerolyl; R%=Ph, Tol)
and on the influence of the carbohydrato substituent
on the diastereoselectivity of the CO/phosphane
exchange in the manganese complexes [6–8]. Photoly-
sis of the chiral carbohydratocarbene complexes in
the presence of phosphanes or phosphites (PR3)
afforded the chiral-at-metal carbene complexes [Cp-
(CO)(PR3)MꢀC(OR*)R%]. The diastereoselectivity of
Chiral transition metal complexes play a prominent
role in enantioselective synthesis and catalysis. In these
complexes the chiral information is either localized
within the ligand sphere or at the metal (chiral-at-metal
complexes) [1]. Although a wide variety of aminoacids
and carbohydrates are available from the chiral pool,
the number of reports on their use as chiral auxiliaries
for the synthesis of chiral-at-metal complexes is rather
restricted.
In recent years, interest has focused on the transfor-
mation of carbohydrates via organometallic com-
pounds especially via transition metal carbene
complexes [2]. The first synthesis of carbohydratocar-
bene complexes was reported by Beck et al. in 1990 [3].
* Corresponding author. Tel.: +49-7531-882783; fax: +49-7531-
883136.
E-mail address: hfischer@dg6.chemie.uni-konstanz.de (H. Fischer).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00753-1

K. Weißenbach, H. Fischer / Journal of Organometallic Chemistry 621 (2001) 344–351
345
the substitution varied considerably and depended on
the type of carbohydrato substituent and on the enter-
ing PR3. The observed diastereomeric excess (de) values
ranged from 0% to higher than 96%. In general, the
diastereoselectivity increased with increasing nucleo-
philicity of PR3 and increasing flexibility of the alkoxy
substituent. When 1,2-O-isopropylideneglycerol was
used as the carbene substituent, within error limits
complete stereocontrol of the replacement of CO by
PR3 was achieved independent of the entering phospho-
rus compound. (R)-1,2-O-Isopropylideneglycerol gave
rise to the formation of complexes with the S configu-
ration at manganese (SMn) and, conversely, (S)-1,2-O-
isopropylideneglycerol afforded the RMn complexes [8].
As a working hypothesis we assumed that the ‘coor-
dinatively unsaturated’ species resulting from photoin-
duced loss of a CO ligand from the carbene(dicarbonyl)
complexes is stabilized by intramolecular chelating in-
teraction of the b-alkoxy group with the free coordina-
tion site at the metal (see Fig.1, A and B) thus also
determining the stereoselectivity of the reaction. How-
ever, it was not possible to detect any chelating inter-
mediate.
We therefore extended our investigations to b-
aminoalcohols and now report on the synthesis of
chiral dicarbonyl aminoalkylidenealkoxycarbene com-
plexes and on the diastereoselectivity of the CO/PR3
exchange in these complexes.
2. Results and discussion
Reaction of the lithium benzoylmanganate 1 with
one equivalent of acetyl bromide in dichloromethane at
−50°C gave the thermolabile acetoxy carbene complex
2 as described previously [7]. When 1.5 equivalent of
N,N-dimethyl alaninol (3) was added, the color of the
solution changed immediately from red to brown and
the w(CO) absorptions shifted towards smaller wave
numbers. Chromatographic work-up afforded the car-
bene complex 8 (Scheme 1) as a red oil in 57% yield.
The analogous reactions of 2 with N,N-dimethyl
valinol (4), N,N-dimethyl leucinol (5), N,N-dimethyl
phenylalaninol (6), and N-formyl prolinol (7) gave the
complexes 9–12 (Scheme 1) in (after chromatography)
58–79% yield. All complexes are stable at room tem-
perature and in air. They are readily soluble in polar
solvents such as dichloromethane, THF, diethyl ether
and toluene, but almost insoluble in pentane. As ex-
pected, for all complexes 8–12 two w(CO) absorptions
of nearly equal intensity are observed in
dichloromethane. The positions of these absorptions
are almost independent of the aminoalcohol-substituent
OR* but are at ca. 20 cm−1 smaller wave numbers than
those of the corresponding glycerol-substituted com-
plexes [8]. In contrast, in pentane complex 9 exhibits
five w(CO) absorptions indicating the presence of an
equilibrium mixture of at least three isomers, pre-
Fig. 1. Possible stabilization of the ‘coordinatively unsaturated’ car-
bene complex by intramolecular chelating interaction.
Scheme 1.

346
K. Weißenbach, H. Fischer / Journal of Organometallic Chemistry 621 (2001) 344–351
determination of the diastereomeric excess by NMR
spectroscopy rather difficult. The de values were deter-
mined by integration of the cyclopentadienyl reso-
nances. For the P(OMe)3-substituted complexes the de
values were additionally confirmed by those obtained
by integration of the OMe signals of the trimethylphos-
phite substituent. The diastereomeric excess determined
for the complexes 17–20 varies between 28 and 46%. In
contrast, for freshly prepared 13 and 14 only one
diastereomer could be detected (de\90%). However,
within several days the de value decreased to ca. 30%
due to epimerization. The diastereomeric excess thus
determined is in qualitative agreement with the 31P-
NMR spectra which are similar to those of the related
isopropylideneglycerol-substituted carbene complexes
[8].
Based on the influence on the diastereoselectivity the
different aminoalcohols can be divided into two groups:
those with a monosubstituted carbon substituent R=
CH2R% at the Cb atom of –O–CaH2–CbHR–NMe2
group (5–7) and 4 which carries a disubstituted carbon
atom CMe2H at Cb. A very high diastereoselectivity
(\90%) independent of the entering PR3 is only ob-
served with complexes 13 and 14 derived from 4. The
de of 17–20 (with a CH2R% substituent at Cb) is only
moderate and in the range 28–46%. Surprisingly, N-
formyl prolinol exerts only a modest influence on the
diastereoselectivity [46% (19) and 34% (20)] although it
is the aminoalcohol sterically most closely related to
1,2-O-isopropylideneglycerol investigated earlier (de\
96% independent of PR3). Obviously, the substituent at
Cb exerts the most influence on the stereoselectivity of
the substitution reaction.
Since it was not possible to detect a chelating inter-
mediate in any of these substitution reactions by IR
spectroscopy, we extended our investigations to mer-
captoalcohol-substituted carbene complexes. It is well
known that the coordinating ability of thioethers to
low-valent complexes is superior to that of amines. We
therefore reasoned that by use of a mercaptoalcohol-
substituent we will have a better chance of generating
and identifying the chelating complex and subsequently
transforming it into a carbene(carbonyl)cyclopenta-
dienyl(PR3)manganese complex.
When a solution of 2 in dichloromethane was
charged with 1.5 equivalent of the b-mercaptoalcohol
derivative 21 and then allowed to warm to a maximum
of −15°C, the formation of a new dicarbonyl complex
was detected by IR spectroscopy. Chromatographic
work-up on silica afforded the mercapto(phenyl)-
carbene complex 22 in ca. 76% yield (Scheme 3). How-
ever, when the solution was allowed to warm to a
temperature higher than −5°C and then kept at that
temperature, the major product isolated after chro-
matography was the thioether complex 23 (Scheme 3).
Scheme 2.
sumably rotational isomers. A resonance in the 13C-
NMR spectrum at rather low field (l=333.4–334.3)
confirms the structure shown in Scheme 1. The reso-
nance of the carbene carbon atom in the related galac-
topyranosyl-, glucopyranosyl-, and isopropylidene-
glycerol-substituted carbene complexes prepared earlier
is observed in the same range [8]. In contrast to the
latter complexes and to 11, for 8–10 and 12 only one
CO resonance is observed indicating rapid rotation
around the Mn–C(carbene) bond or the presence of a
pseudo-mirror plane.
Photolysis of 9–12 in toluene in the presence of 1.5
equivalent of tritolylphosphane or trimethylphosphite
at
−30°C
afforded
the
carbene(carbonyl)-
(cyclopentadienyl)(PR3)manganese complexes 13–20
(Scheme 2).
The product complexes also turned out to be photo-
labile and decomposed quickly on prolonged irradia-
tion to form Cp(CO)3Mn and unidentified products
thus limiting irradiation to ca. 3–6 min. Total transfor-
mation of the dicarbonyl complexes 10–12 led to low
yields. The most photosensitive complexes were the
leucinol-substituted complexes 15 and 16. Despite very
short irradiation times it was not possible to isolate
these complexes free from large amounts of impurities.
The formation of these complexes was therefore estab-
lished by their IR spectra only. All other complexes (13,
14, 17–20) were isolated in yields ranging from 42 (13)
to 85% (20).
The complexes 14 and 17 are rather labile and de-
compose at ambient temperature within a few days, in
solution (acetone) even within a few hours. All other
complexes are stable at room temperature and in air. In
dichloromethane, all complexes 13–20 exhibit only one
w(CO) absorption each. Its position is nearly indepen-
dent of the aminoalcohol substituent. As expected, the
absorption of the P(OMe)3-substituted complexes is at
18–20 cm−1 higher wave number compared to that of
the PTol3-substituted compound. The spectra in pen-
tane indicate the presence of rotational isomers.
1
The complicated structure of the H-NMR spectra
with its many overlapping resonances renders the exact

K. Weißenbach, H. Fischer / Journal of Organometallic Chemistry 621 (2001) 344–351
347
3. Experimental
Complex 23 was presumably formed via displace-
ment of the carbene ligand in 22 (or 2) by free 21 which
was present in excess. The constitution of 23 was
established by spectroscopic means (IR, NMR, and
mass spectroscopy) and by an independent synthesis
from [Cp(CO)3Mn] and 21.
3.1. General
All operations were carried out under either nitrogen
or argon by using conventional Schlenk techniques.
Solvents were dried by refluxing over sodium–ben-
zophenone ketyl or CaH2 and were freshly distilled
prior to use. The silica gel used for chromatography
(J.T. Baker, silica gel for flash chromatography) was
saturated with argon. The yields refer to analytically
pure compounds and were not optimized. The com-
plexes 1 [9] and 2 [7], the aminoalcohols N,N-dimethyl
alaninol (3), N,N-dimethyl leucinol (4), N,N-dimethyl
valinol (5), N,N-dimethyl phenylalaninol (6), [10,11]
and N-formylprolinol (7) [12] as well as PTol3 [13] were
prepared according to literature procedures. P(OMe)3
and acetyl bromide were purchased from Fluka. IR:
FT-IR spectrophotometer, Bio-Rad. 1H-NMR, 31P-
NMR and 13C-NMR: Bruker WM 250, Bruker AC
250, Bruker DRX 600, Jeol JNX 400. Unless specifi-
cally mentioned, 1H-NMR spectra were recorded at 250
MHz and 13C- and 31P-NMR spectra at 400 MHz. All
spectra were recorded at room temperature (r.t.) in
CD3COCD3. Chemical shifts are reported relative to
the residual solvent peaks (1H l=2.05 and 13C l=
29.8) or to external H3PO4 (31P). MS: Finnigan MAT
312 (EI) or Finnigan MAT 312/AMD5000 (FAB).
From the observation of six w(CO) absorptions in the
IR spectrum of the carbene complex 22 in pentane it
follows that at least three rotamers of 22 are present in
solution. In contrast, the NMR spectra exhibit only one
set of resonances indicating that isomerization is rapid
with respect to the NMR time-scale.
Irradiation of a solution of 22 in dichloromethane at
−30°C for a few minutes led to the formation of a new
complex which in the IR spectrum showed only one
absorption at 1854 cm−1 and whose mass spectrum is
in accordance with the constitution (24) shown in
Scheme 3. Although 24 proved to be stable in solution
at temperatures below 0°C for a short period of time, it
could not be isolated in a pure form. On chromatogra-
phy compound 24 quickly decomposed. When
triphenylphosphane or trimethylphosphite was added
to solutions of 24 in dichloromethane no reaction was
observed, neither at −50°C (for 50 h) nor at elevated
temperatures. In boiling dichloromethane only decom-
position of 24 and the formation of [Cp(CO)3Mn] in
addition to other unidentified products were observed.
Presumably due to the high stability of the Mn–S
bond, thermal opening of the C,S-chelate ring requires
temperatures at which either the chelate complex or the
substitution product quickly decompose. Whether Mn–
S dechelation of 24 and addition of PR3 to the resulting
free coordination site can be induced photochemically
is at present under investigation.
3.2. General procedure for the synthesis of the
complexes 8–12
At −50°C 4.5 mmol of the corresponding aminoal-
cohol derivative (3–7) was added to a solution of 2,
prepared from 3.0 mmol of acetyl bromide and 3.0
mmol of 1 in 50 ml of CH2Cl2. The resulting solution
was stirred for 0.5 h at −50°C, warmed to 0°C and
stirred for another 2.5 h at 0°C. The solvent was
removed at r.t. in vacuo. The dark brown residue was
dissolved in CH2Cl2–pentane (2/1) and chro-
matographed at −30°C on silica gel first with CH2Cl2–
pentane and then with CH2Cl2–pentane–triethylamine.
3.2.1. Dicarbonyl(cyclopentadienyl)[(2S)-2-N,N-
dimethylamino-propane-1-yloxy(phenyl)carbene]-
manganese (8)
Chromatography with CH2Cl2–pentane (6/1) af-
forded a yellow band (30 mg) and then elution with
CH2Cl2–pentane–NEt3 (2/1/0.3) gave a red–brown
band. Removal of the solvent from the red–brown
fraction afforded complex 8 as a red oil. Yield: 500 mg
Scheme 3.

348
K. Weißenbach, H. Fischer / Journal of Organometallic Chemistry 621 (2001) 344–351
(57% relative to 1). IR (pentane) w(CO) (cm−1): 1972
m, 1962 vs, 1914 m, 1900 vs. H-NMR: l=1.08 (d,
(100) [(CH2CH(NMe2)CH2CH(CH3)2)+], 120 (6)
[MnCp+], 58 (32) [CH2CH(CH3)2+], 55 (27) [Mn+].
Anal. Found: C, 66.24; H, 7.50; N, 3.70. Calc. for
C22H28MnNO3·0.3C5H12 (433.4): C, 65.77; H, 7.44; N,
3.33%.
1
3J=6.7 Hz, 3 H, CH3), 2.24 (s, 6 H, N(CH3)2), 2.77–
3.05 (m, 1 H, CH), 4.30–4.50 (m, 2 H, CH2), 4.69 (s, 5
H, Cp), 6.96–6.99 (m, 2 H, Ph), 7.22–7.39 (m, 3 H,
Ph). 13C-NMR: l=12.6 (CH3), 41.6 (NCH3), 42.6
(CH2), 59.3 (CHN), 74.0 (OCH2), 88.0 (Cp), 123.5,
127.9, 1128.9, 135.6, 155.8 (Ph), 233.1 (CO), 334.3
(MnꢀC). MS (EI, 70 eV) m/z (%): 367 (11) [M+], 311
(11) [M+−2CO], 197 (28) [CpMnPh+], 120 (18)
[CpMn+], 86 (100) [NMe2CH(CH3)CH+2 ], 55 (75)
[Mn+]. Anal. Found: C, 63.78; H, 6.75; N, 3.16. Calc.
for C19H22MnNO3 (395.4): C, 63.79; H, 6.63; N, 3.54%.
3.2.4. Dicarbonyl(cyclopentadienyl)[(2S)-2-N,N-
dimethylamino-3-phenyl-propane-1-yloxy(phenyl)-
carbene]manganese (11)
Chromatography with CH2Cl2–pentane (2/1) gave
first a yellow and then a red band. Subsequent elution
with CH2Cl2–pentane–diethyl ether–NEt3 (1/2/0.6/0.4)
afforded a yellow band which was collected. Removal
of the solvent from this fraction in vacuo yielded com-
plex 11 (1.58 g, 73% relative to 1) as a brown oil. IR
3.2.2. Dicarbonyl(cyclopentadienyl)[(2S)-2-N,N-
dimethylamino-3-methyl-butane-1-yloxy(phenyl)-
carbene]manganese (9)
1
(CH2Cl2) w(CO) (cm−1): 1955 vs, 1887 vs. H-NMR:
l=2.38 (br, 6 H, N(CH3)2), 2.18–2.21 (m, 1 H, CH),
2.75–2.97 (m, 4 H, CH2O, CH2Ph), 4.66 (s, 5 H, Cp),
6.90–7.35 (m, 10 H, Ph). 13C-NMR: l=34.3 (CH2Ph),
41.7 (N(CH3)2), 65.8 (CH), 75.7 (CH2O), 87.9, 88.0
(Cp), 123.2, 126.6, 128.1, 129.2, 140.7, 155.5 (Ph, Bn),
232.8, 233.0 (CO), 334.1 (MnꢀC). MS (EI, 70 eV) m/z
(%): 415 (0.2) [M+−CO], 371 (13) [M+−
CH2CHNMe2], 120 (58) [MnCp+], 105 (100)
[(CH3CH2Ph)+], 91 (25) [C7H7+], 77 (63) [C6H+5 ], 55
(63) [Mn+]. It was not possible to to obtain complex 11
in an analytically pure form free of NEt3.
Chromatography with CH2Cl2–pentane (2/1) gave a
dark red band (30 mg). Subsequently, elution with
CH2Cl2–pentane–NEt3 (1/2/0.3) afforded a red–brown
band which was collected. Removal of the solvent from
the second fraction in vacuo yielded complex 9 (630
mg, 67% relative to 1) as a red oil. IR (CH2Cl2) w(CO)
1
(cm−1): 1955 vs, 1884 vs. H-NMR: l=0.92, 0.98 (d
3
each, J=6.6 Hz, together 6 H, CH(CH3)2), 2.29 (s, 6
H, N(CH3)2), 2.39–2.45 (m, 1 H, CH), 4.39–4.60 (m, 2
H, CH2), 4.68 (s, 5 H, Cp), 6.20–6.97 (m, 2 H, Ph),
7.22–7.39 (m, 3 H, Ph). 13C-NMR: l=20.2, 21.1
(CH3), 28.6 (NCH3), 42.1 (CH(CH3)2), 69.8 (CHN),
74.0 (OCH2), 88.1 (Cp), 123.1, 127.7, 128.2, 156.1 (Ph),
233.1 (CO), 334.0 (MnꢀC). MS (EI, 70 eV) m/z (%):
395 (0.4) [M+], 339 (0.2) [M+−2CO], 197 (7) [CpM-
nPh+], 114 (100) [(CH2CH(NMe2)CH(CH3)2)+], 58
(100) [CH2CH(CH3)+2 ], 55 (98) [Mn+]. Anal. Found: C,
63.78; H, 6.75; N, 3.16. Calc. for C21H26MnNO3
(395.4): C, 63.79; H, 6.63; N, 3.54%.
3.2.5. Dicarbonyl(cyclopentadienyl)[(2S)-N-
formyl-pyrrolidine-2-methylenyloxy(phenyl)carbene]-
manganese (12)
Chromatography with CH2Cl2–pentane (2/1) gave
first a dark red band. Subsequent elution with CH2Cl2–
pentane–NEt3 (1/2/0.3) afforded a red–brown band
which was collected. Removal of the solvent from this
fraction in vacuo yielded complex 12 (840 mg, 58%
relative to 1) as a red oil. IR (CH2Cl2) w(CO) (cm−1):
1955 vs, 1884 vs. 1H-NMR: l=1.75–2.03 (m, 4 H,
3-CH2, 4-CH2), 3.20–3.75 (m, 3 H, 5-CH2, 2-CH), 4.37
(br, 2 H, CH2O), 4.69, 4.71 (s each, together 5 H, Cp),
6.87–6.97 (m, 2 H, Ph), 7.26–7.42 (m, 3 H, Ph), 8.24,
8.30 (br, together 1 H, CHO). 13C-NMR: l=28.9, 29.0
(3-CH2, 4-CH2), 43.3 (5-CH2), 46.9 (2-CH), 75.5, 77.9
(OCH2), 87.5, 88.1 (Cp), 122.6, 127.2, 127.6, 128.1,
128.5, 128.6, 154.4, 154.8 (Ph), 232.0 (CO), 333.4, 333.5
(MnꢀC), CHO not detected. MS (EI, 70 eV) m/z (%):
393 (10) [M+], 337 (24) [M+−2CO], 120 (74) [MnCp+
], 55 (100) [Mn+]. Anal. Found: C, 60.41; H, 6.07; N,
3.13. Calc. for C20H20MnNO4 (393.3): C, 61.07; H,
5.13; N, 3.56%.
3.2.3. Dicarbonyl(cyclopentadienyl)[(2S)-2-N,N-
dimethylamino-4-methyl-pentane-1-yloxy(phenyl)-
carbene]manganese (10)
Chromatography with CH2Cl2–pentane (2/1) gave a
dark red band. Subsequent elution with CH2Cl2–pen-
tane–NEt3 (1/2/0.3) afforded a dark brown band which
was collected. Removal of the solvent from this fraction
in vacuo yielded complex 10 (1.06 g, 79% relative to 1)
as a red oil. IR (pentane) w(CO) (cm−1): 1972 s, 1963
vs, 1914 s, 1908 s, 1900 vs. 1H-NMR: l=0.81–0.95 (m,
6 H, –CH(CH3)2), 1.18–1.37, 1.42–1.51 (m each, to-
gether 2 H, CH2), 1.54–1.94 (m, 1 H, CH), 2.28 (s, 6 H,
N(CH3)2), 2.86–3.01 (m, 1 H, CH), 4.01–4.49 (m, 2H,
CH2).4.68 (s, 5H, Cp), 6.95–6.98 (m, 1H, Ph), 7.64 (m,
4 H, Ph). 13C-NMR: l=22.6, 23.4 (CH3), 25.4
(NCH3), 38.4 (CH2), 41.2 (CH(CH3)2), 61.2 (NCH),
76.6 (OCH2), 88.0 (Cp), 123.3, 127.6, 127.8, 128.2,
155.8 (Ph), 233.1 (CO), 334.2 (MnꢀC). MS (EI, 70 eV)
m/z (%): 409 (0.6) [M+], 353 (0.3) [M+−2CO], 128
3.3. General procedure for the synthesis of the complexes
13–20
A solution of 0.6 mmol of 9–12 and 0.9 mmol of the
corresponding PR3 in 30 ml of toluene was irradiated at

K. Weißenbach, H. Fischer / Journal of Organometallic Chemistry 621 (2001) 344–351
349
−30°C (for the irradiation time see below). To remove
CO a slow stream of argon was passed through the
solution. The solvent was removed at r.t. in vacuo.
The residue was dissolved in CH2Cl2–pentane (2/1) and
chromatographed at −20°C on silica gel with CH2Cl2–
pentane–diethyl ether–triethylamine (2/1/0.3/0.3).
only established by its IR spectrum in CH2Cl2 w(CO):
1832 cm−1
.
3.3.4. Carbonyl(cyclopentadienyl)[(2S)-2-N,N-
dimethylamino-4-methyl-pentane-1-yloxy(phenyl)-
carbene](trimethylphosphite)manganese (16)
PR3=P(OMe)3, irradiation of 10 for 3.0 min. During
irradiation, complex 16 rapidly decomposed again and
therefore could not be isolated free of large amounts of
impurities. Its intermediary formation was only estab-
3.3.1. Carbonyl(cyclopentadienyl)[(2S)-2-N,N-dimethyl-
amino-3-methyl-butane-1-yloxy(phenyl)carbene]-
(tritolylphosphane)manganese (13)
PR3=P(C6H4CH3-p)3, irradiation time 5 min. Chro-
matography with CH2Cl2–pentane–NEt3 (1/2/0.3) af-
forded complex 13 (120 mg, 42% relative to 9) as a
\95:5 mixture of diastereomers (de\90%) in the form
of an orange oil. IR (CH2Cl2) w(CO) (cm−1): 1833 s.
1H-NMR: l=0.77–1.03 (m, together 6 H, CH(CH3)2),
lished by its IR spectrum in CH2Cl2 w(CO): 1852 cm−1
.
3.3.5. Carbonyl(cyclopentadienyl)[(2S)-2-N,N-
dimethylamino-3-phenyl-propane-1-yloxy(phenyl)-
carbene](tritolylphosphane)manganese (17)
PR3=P(C6H4CH3-p)3, irradiation time 4.5 min.
Chromatography with CH2Cl2–pentane–NEt3 (1/2/0.3)
afforded complex 17 (270 mg, 62% relative to 11) as a
36:64 mixture of diastereomers (de 28%) in the form of
an orange oil. IR (CH2Cl2) w(CO) (cm−1): 1834 vs.
1H-NMR: l=2.12–2.57 (m, 16 H, N(CH3)2, C6H4CH3,
CH), 2.75–3.08 (m, 4 H, CH2O, CH2Ph), 4.38, 4.43 (s
each, together 5 H, Cp), 6.80–7.95 (m, 22 H, Ph,
C6H4CH3). MS (FAB, NBA) m/z (%): 719 (0.8) [M+],
691 (1) [M+−2CO]. Anal. Found: C, 75.58; H, 7.09;
N, 2.28. Calc. for C45H46MnNO2P (718.8): C, 75.20; H,
6.45; N, 1.95%.
2.21–2.39 (m, 17 H, N(CH3)2, C6H4CH3, CHN,
3
CH(CH3)2), 3.43–3.88 (m, 2 H, CH2), 4.40 (d, JPH
=
1.7 Hz, 5 H, Cp), 6.58–6.67 (m, 2 H, Ph), 6.94–7.67
(m, 15 H, arom.). 13C-NMR: l=21.2, 21.4 (CH3), 25.8
(NCH3), 41.3, 41.5, 41.7 (CH(CH3)2), 63.5, 63.8, 64.2,
65.0 (CHN), 72.3, 72.6 (OCH2), 87.1, 87.3, 87.4 (Cp),
123.3, 125.5, 125.7, 126.5, 126.7, 126.8, 127.1, 127.4,
128.2, 128.7, 128.9, 129.0, 129.3, 129.6, 129.9, 130.6,
132.7, 133.8, 136.1, 136.3, 139.7, 142.8 (arom.), 237.9
(CO), 326.6 (MnꢀC). 31P-NMR: l=84.1, 84.3, 89.9.
MS (EI, 70 eV) m/z (%): 643 (0.1) [M+−CO], 304 (53)
[PTol+3 ], 114 (39) [CH2CH(NMe2)CHMe+2 ], 100 (100)
[NMe2CHCHMe+2 ], 58 (36) [CH2CH(CH3)+2 ].
3.3.6. Carbonyl(cyclopentadienyl)[(2S)-2-N,N-
dimethylamino-3-phenyl-propane-1-yloxy(phenyl)-
carbene](trimethylphosphite)manganese (18)
3.3.2. Carbonyl(cyclopentadienyl)[(2S)-2-N,N-
dimethylamino-3-methyl-butane-1-yloxy(phenyl)carbene]-
(trimethylphosphite)manganese (14)
PR3=P(OMe)3, irradiation time 5 min. Orange oil.
Ratio of diastereomers 31:69 (de=38%). Yield: 170 mg
(52% based on 11). IR (CH2Cl2) w(CO) (cm−1): 1852
PR3=P(OMe)3, irradiation time 6 min. Chromatog-
raphy with CH2Cl2–pentane–NEt3 (1/2/0.3) afforded
complex 14 (200 mg, 67% relative to 9) as a \95:5
mixture of diastereomers (de\90%) in the form of an
orange oil. IR (CH2Cl2) w(CO) (cm−1): 1851 s. 1H-
NMR: l=0.92–0.99 (m, 6 H, CH(CH3)2), 1.80–1.95
(m, 1 H, CH), 2.30 (s, 6 H, N(CH3)2), 2.39–2.45 (m, 1
H, CH(CH3)2), 3.62, 3.63 (d each, 3JPH=11 Hz, to-
gether 9 H, P(OCH3)3), 4.46–4.67 (m, 2 H, CH2), 4.42,
1
vs. H-NMR: 2.11–2.21 (m, 1 H, CH), 2.30, 2.34 (s
each, 6 H, N(CH3)2), 2.68–3.20 (m, 4 H, CH2O,
3
CH2Ph), 3.57 and 3.59 (d each, JPH=11.5 and 11.0
Hz, together 9 H, P(OCH3)3), 4.41–4.44 (m, 5 H, Cp),
6.93–7.53 (m, 10 H, Ph). 13C-NMR: l=40.5, 40.6
(CH2Ph), 51.3, 51.4 (P(OCH3)3), N(CH3)2), 57.9
(CHN), 64.3 (CH), 69.0 (CH2O), 85.6, 85.7 (Cp), 125.7,
125.9, 126.1, 126.6, 127.9, 128.2, 128.3, 128.4, 128.5,
128.9, 129.2, 129.3, 129.4, 140.3, 140.6, 155.4, 156.5
(Ph, Bn), 235.9, 236.3 (CO), 324.6, 324.9 (MnꢀC).
31P-NMR: l=204.7, 211.3, 214.5. MS (EI, 70 eV) m/z
(%): 539 (4) [M+], 244 (17) [CpMn[P(OMe)3]+], 162
(100)[(CH2C(NMe2)CH2Ph)+], 148(84)[(Me2NCHCH2-
Ph)+], 146 (95) [(C10H12N)+].
3
4.41 (d each, JPH=1.7 Hz, together 5H, Cp), 6.95–
7.36 (m, 5 H, Ph). 31P-NMR: l=204.6. MS (EI, 70 eV)
m/z (%): 491 (0.4) [M+], 339 (1.2) [M+−CO–L], 244
(17) [CpMn[P(OMe)3]+], 100 (100) [Me2CHNMe+2 ],
114 (57) [Me2CH(CH2)NMe+2 ], 58 (42) [CH2CH(CH3)2+].
3.3.3. Carbonyl(cyclopentadienyl)[(2S)-2-N,N-
dimethylamino-4-methyl-pentane-1-yloxy(phenyl)-
3.3.7. Carbonyl(cyclopentadienyl)[(2S)-N-
carbene](tritolylphosphane)manganese (15)
formyl-pyrrolidine-2-methylenyloxy(phenyl)carbene]-
(tritolylphosphane)manganese (19)
PR3=P(C6H4CH3-p)3, irradiation time 6 min. Chro-
matography with CH2Cl2–pentane–NEt3 (1/2/0.3) af-
forded complex 19 (320 mg, 82% relative to 12) as a
PR3=P(C6H4CH3-p)3, irradiation of 10 for 3.5 min.
During irradiation, complex 15 rapidly decomposed
again and therefore could not be isolated free of large
amounts of impurities. Its intermediary formation was

350
K. Weißenbach, H. Fischer / Journal of Organometallic Chemistry 621 (2001) 344–351
27:73 mixture of diastereomers (de=46%) in the form
of an orange oil. IR (CH2Cl2): w(CO) (cm−1) 1833 s.
1H-NMR: l=1.85–2.23 (m, 4 H, 3-CH2, 4-CH2), 2.38
(s, 9 H, C6H4CH3), 3.20–3.75 (m, 3 H, 5-CH2, 2-CH),
4.31 (m, 2 H, CH2O), 4.42, 4.44 (s each, together 5 H,
Cp), 7.16–7.65 (m, 5 H, Ph), 8.27, 8.39 (br, together 1
H, CHO). 13C-NMR: l=21.2, 21.4 (C6H4CH3), 23.3,
28.4 (3-CH2, 4-CH2), 43.9 (5-CH2), 47.3 (2-CH), 72.8,
75.5 (OCH2), 87.6 (Cp), 125.6, 126.9, 127.3, 128.7,
129.3, 130.0, 132.8, 133.8, 134.2, 135.8, 136.0, 139.4,
139.9, 142.8, 155.4, 164.8 (Ph), 238.3 (CO), 324.0
(MnꢀC). 31P-NMR: l=82.9, 83.5. MS (FAB, NBA)
m/z (%): 699 (3) [M+], 641 (3) [M+−2CO]. Anal.
Found: C, 71.48; H, 6.50; N, 1.88. Calc. for
C40H41MnNO3P (669.7): C, 71.74; H, 6.17; N, 2.09%.
relative to 1). IR (pentane) w(CO) (cm−1): 1983 sh,
1
1973 sh, 1965 vs, 1923 sh, 1915 sh, 1903 vs. H-NMR:
3
l=2.90 (t, J=6.42 Hz, 2 H, OCH2CH2SBn), 3.78 (s,
2
H, CH2Ph), 4.54 (t, 3J=6.42 Hz,
2
H,
OCH2CH2SBn), 4.71 (s, 5 H, Cp), 6.74–7.04 (m, 1 H,
arom.), 7.23–7.31 (m, 2 H, arom.), 7.32–7.38 (m, 7 H,
arom.). 13C-NMR: l=36.0 (SCH2Bn), 75.5, 81.8
(OCH2CH2SBn), 87.4 (Cp), 122.8, 127.3, 127.5, 128.4,
128.9, 138.6, 154.9 (Ph, Bn), 232.0 (CO), 333.4 (MnꢀC).
MS (EI, 70 eV) m/z (%): 432 (3) [M+], 376 (4) [M+−
2CO], 151 (70) [(CH2CH2SBn)+], 120 (10) [MnCp+], 91
(100) [C7H+7 ], 55 (40) [Mn+]. Anal. Found: C, 63.82; H,
5.03. Calc. for C23H21MnO3S (432.4): C, 63.89; H,
4.89%.
3.5. Dicarbonyl(cyclopentadienyl)[1-benzylmercapto-
ethane-2-ol-S]manganese (23)
3.3.8. Carbonyl(cyclopentadienyl)[(2S)-N-
formyl-pyrrolidine-2-methylenyloxy(phenyl)carbene]-
(trimethylphosphite)manganese (20)
The reaction of 250 mg (1.5 mmol) of 1-benzylmer-
captoethane-2-ol with 2 and the subsequent chromatog-
raphy were carried out as described in Section 3.4,
except that the solution was allowed to warm to r.t.
and was stirred at r.t. for 3 h. On chromatography
first an orange–red fraction (containing 22) and then
with CH2Cl2–pentane–Et2O (2/1/0.3) a dark red–
brown band were eluted. Removal of the solvent from
the second fraction gave 23 in the form of an orange
oil. Yield: 280 mg (54% based on 1). IR (pentane)
PR3=P(OMe)3, irradiation time 6 min. Chromatog-
raphy afforded complex 20 (200 mg, 85% relative to 12)
as a 33:67 mixture of diastereomers (de=34%) in the
form of an orange oil. IR (CH2Cl2) w(CO) (cm−1): 1851
1
s. H-NMR: l=1.79–2.19 (m, 4 H, 3-CH2, 4-CH2),
3.30–3.34 (m, 2 H, 5-CH2), 3.52 and 3.61 (d each,
3JPH=11.6 and 11.1 Hz, 9 H, P(OCH3)3), 3.49–3.55
(m, 1 H, 2-CH), 4.01–4.37 (m, 2 H, CH2O), 4.42, 4.44
3
(d each, JPH=1.46 and 1.65 Hz, 5 H, Cp), 7.07–7.48
1
w(CO) (cm−1): 1938 vs, 1874 vs. H-NMR: 2.74 (br, 2
(m, 5 H, Ph). 13C-NMR: l=22.6, 22.7, 23.7, 23.8
(CH3), 27.8, 27.9, 28.0 (NCH3), 43.3, 46.5 (CH(CH3)2),
51.4 (P(OCH3)3), 56.6, 56.7 (CHN), 76.4, 78.9 (OCH2),
85.7, 85.8 (Cp), 124.2, 126.2, 126.7, 128.0, 128.4, 128.7,
156.0, 156.2, 156.5 (Ph), 238.3 (m, CO), 324.0 (m,
MnꢀC). 31P-NMR: l=203.6, 210.8, 214.6. MS (EI, 70
eV) m/z (%): 491 (0.4) [M+], 339 (1.2) [M+−CO–L],
244(17)[MnCp[P(OMe)3]+], 100 (100) [Me2CHNMe2+],
114 (57) [Me2CH(CH2)NMe+2 ], 58 (42) [CH2CH(CH3)2+].
H, CH2S), 3.87 (br, 2 H, CH2O), 4.05 (br, 1 H, OH),
4.56 (br, 5 H, Cp), 7.47 (br, 5 H, Ph). 13C-NMR:
l=44.5 (CH2SBn), 48.7 (SCH2Ph), 59.5 (CH2OH),
81.8 (Cp), 126.8, 126.7, 128.3, 128.5, 129.0, 129.7, 136.5
(Ph, Bn), 234.1 (CO). MS (EI, 70 eV) m/z (%): 344 (5)
[M+],
288
(28)
[M+−2CO],
168
(52)
[(HOCH2CH2SBn)+], 120 (25) [MnCp+], 91 (100)
[C7H+7 ], 55 (21) [Mn+]. Anal. Found: C, 55.82; H, 5.15.
Calc. for C16H17MnO3S (344.3): C, 55.82; H, 4.98%.
3.4. Dicarbonyl(cyclopentadienyl)[1-benzyl-
mercaptoethane-2-yloxy(phenyl)carbene]manganese (22)
3.6. Generation of monocarbonyl(cyclopentadienyl)-
[1-benzylmercaptoethane-1-yloxy-S-(phenyl)carbene]-
manganese (24)
760 mg (4.5 mmol) of 1-benzylmercaptoethane-2-ol
(21) was added at −50°C to a solution of 2 freshly
prepared from 860 mg (3.0 mmol) of 1, 0.43 ml (3.0
mmol) of TMEDA and 0.21 ml (3.0 mmol) of acetyl-
bromide in 50 ml of CH2Cl2. Within 2 h, the solution
was allowed to warm up to −15°C and stirred for
another 2 h at −15°C. The solvent was removed at r.t,
in vacuo. The residue was dissolved in 12 ml of
CH2Cl2–pentane (1/2) and chromatographed on silica
at −30°C with CH2Cl2–pentane (1/2). An orange frac-
tion was eluted which, after removal of the solvent in
vacuo, afforded a dark brown oil. Yield: 1.29 g (76%
A solution of 260 mg (0.6 mmol) of 22 in 30 ml of
CH2Cl2–pentane (1/1) was irradiated for 4.5 min at
−30°C, while a slight Ar stream was passed through
the solution. The solvent was then removed in vacuo at
a temperature below −30°C. All attempts to purify the
product by column chromatography failed since, even
at very low temperature, the complex 24 decomposed
on contact with silica. IR (CH2Cl2, −30°C) w(CO):
1854 s cm−1. MS (EI, 70 eV) m/z (%): 404 (0.4) [M+],
390 (0.7) [M+−CH2], 376 (2) [M+−CO], 120 (10)
[MnCp+], 91 (100) [C7H7+], 55 (29) [Mn+].

K. Weißenbach, H. Fischer / Journal of Organometallic Chemistry 621 (2001) 344–351
351
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Acknowledgements
[5] K.H. Do¨tz, W. Straub, R. Ehlenz, K. Peseke, R. Meisel, Angew.
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1856.
Support of this work by the Fonds der Chemischen
Industrie is gratefully acknowledged.
[6] H. Fischer, J. Schleu, G. Roth, Chem. Ber. 128 (1995)
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[7] H. Fischer, J. Schleu, Chem. Ber. 129 (1996) 385.
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