Aminorhenium carbon dioxide complexes: Formal oxidation of a carbon monoxide ligand with peroxy-acids or bromine/hydroxide

Article abstract of DOI:10.1016/j.jorganchem.2003.09.051

The electron-rich aminorhenium complexes η⁵ :η¹-C₅H₄CH₂ CH₂NR(CH₃)Re(CO)₂ (3a-d; R=methyl, benzyl, n-butyl, n-butyl-OH) are easily oxidized with peroxy-acids to give the corresponding η²-CO₂ complexes η⁵: η¹- C₅H₄ CH₂CH₂NR(CH₃)Re(CO) (η²-CO₂) (4a-d) in excellent yield. The resultant η²-CO₂ complex is predominantly the anti-isomer. The structures of η²-CO₂ complex η⁵:η¹-C₅H₄CH ₂CH₂N(CH₃)(n- C₄ H₈OH)Re(CO)(η²-CO₂) (4d-anti) and the corresponding CO complex 3d have been confirmed by X-ray crystallography. The η²-CO₂ complexes 4a-4d are stable at ambient temperature under air. In addition to peroxy-acid oxidation, bromination of the aminorhenium dicarbonyl complexes followed by base treatment also provided the corresponding η² -CO₂ complexes. The reaction mechanism for the formation of CO₂ complex from the corresponding dicarbonyl is discussed briefly.

Full text of DOI:10.1016/j.jorganchem.2003.09.051

Journal of Organometallic Chemistry 689 (2004) 411–418
www.elsevier.com/locate/jorganchem
Aminorhenium carbon dioxide complexes: formal oxidation of
a carbon monoxide ligand with peroxy-acids or bromine/hydroxide q
*
Tein-Fu Wang , Chong-Chen Hwu, Yuh-Sheng Wen
Institute of Chemistry, Academia Sinica, Taipei, Taiwan
Received 21 August 2003; received in revised form 18 September 2003; accepted 19 September 2003
Abstract
The electron-rich aminorhenium complexes g5:g1-C5H4CH2CH2NR(CH3)Re(CO)2 (3a–d; R ¼ methyl, benzyl, n-butyl, n-butyl-
OH) are easily oxidized with peroxy-acids to give the corresponding g2-CO2 complexes g5:g1-C5H4CH2CH2NR(CH3)Re(CO)(g2-
CO2) (4a–d) in excellent yield. The resultant g2-CO2 complex is predominantly the anti-isomer. The structures of g2-CO2 complex
g5:g1-C5H4CH2CH2N(CH3)(n- C4H8OH)Re(CO)(g2-CO2) (4d-anti) and the corresponding CO complex 3d have been confirmed by
X-ray crystallography. The g2-CO2 complexes 4a–4d are stable at ambient temperature under air. In addition to peroxy-acid oxi-
dation, bromination of the aminorhenium dicarbonyl complexes followed by base treatment also provided the corresponding g2-CO2
complexes. The reaction mechanism for the formation of CO2 complex from the corresponding dicarbonyl is discussed briefly.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Rhenium; Carbon dioxide; Cyclopentadienyl; Amine; Oxidation
1. Introduction
displaced ligand [2]. For example, g2-CO2 complex
Ni(CO2)(PCy3)2 was prepared by Ni(PCy3)3 or [Ni-
(PCy3)2]2 (l-N2) in toluene under an atmospheric pres-
sure of CO2 [3]. Similarly, Fe(depe)2 (CO2) was made
from Fe(depe)2(N2) and CO2 [4]. There is only few cases
of stable g2-CO2 complex been resulted by a formal
oxidation of metal carbonyl complex. For example,
Cp2Nb(R)(g2-CO2) has been prepared by aerobic oxi-
dation of the corresponding carbonyl complex [5].
Transient CO2 complex (g2-C5H4CH3)2Ta(g2-CO2)H
was formed during the dioxygen oxidation of the cor-
responding metal carbonyl hydride [6]. Excellent reviews
on the coordination chemistry of carbon dioxide have
been reported [7].
We have demonstrated that the electron-rich amino-
rhenium complex reacts readily with a variety of carbon
electrophiles. For instance, bidentate complex [g5:g1-
C5H4CH2CH2N(CH3)2Re(CO)2] reacts with alkyl
halides to give the corresponding adduct [g5:g1-C5H4-
CH2CH2N(CH3)2Re(CO)2 alkyl]þXꢀ [8]. We envisioned
that if ‘‘oxo’’ electrophiles had been used for the reaction,
the resultant ‘‘metal-oxo’’ intermediate might undergo
interesting transformations. Indeed, when aminorhenium
complex was treated with m-chloroperoxybenzoic acid
Carbon dioxide was generally considered as a poor
ligand in organometallic chemistry. Such a property has
been utilized as an advantage in the carbonyl ligand
substitution reactions. A notable example is the tri-
methylamine N-oxide promoted ligand substitution re-
actions of metal carbonyl [1]. In the reaction, the carbon
monoxide ligand was oxidized by N-oxide to a carbon
dioxide ligand followed by CO2 extrusion, due to the
insufficient binding force between the metal and the re-
sultant CO2 ligand. Coordination with a prerequisite
ligand completed the ligand substitution. However, if
the binding force was strong enough to hold the metal
and CO2 together, the resultant CO2 complex could be
stable and isolable. Mononuclear CO2 complexes have
usually been prepared by direct coordination of CO2 to
a metal complex which has a vacant site or an easily
q Supplementary data associated with this article can be found, in the
online version at doi:10.1016/j.jorganchem.2003.09.051.
* Corresponding author. Tel.: +886-2-2789-5696; fax: +886-2-2783-
1237.
E-mail address: tfwang@chem.sinica.edu.tw (T.-F. Wang).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.09.051

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T.-F. Wang et al. / Journal of Organometallic Chemistry 689 (2004) 411–418
(MCPBA), the corresponding g2-CO2 complex was
obtained [9]. Furthermore, oxidation of the metal center
by a bromonium ion followed by base treatment also
provides g2-CO2 complex. It is quite amazing that same
g2-CO2 complex could be produced via two completely
different approaches. In this report, we want to present
such reactions and briefly describe their reaction path-
ways. The diastereoselectivity of the reaction to give syn-
and anti-isomers will also be discussed.
Characterization of the reaction products could be
easily accomplished spectroscopically. Upon coordina-
tion, the N-methyl groups downfield shift to about d
1
3.03 compared to the free amine at d 2.44 in the H
NMR spectra. Owing to the nitrogen chiral center, the
cyclopentadienyl protons of 3b–3d appear as four dis-
crete resonances and the methylene protons of the side
chain appear diastereotopically. The terminal carbonyl
groups of 3b–3d are non-equivalent, as shown by the
different resonance frequencies of the carbonyl carbons
in the 13C NMR spectra. Compound 3d has also been
characterized by X-ray crystallography and the ORTEP
drawing is shown in Fig. 1.
2. Results and discussion
2.1. Preparation of the aminorhenium complexes
Chelated aminorhenium complex 2 was prepared by
ultraviolet irradiation of the monomethylamino rhe-
nium tricarbonyl complex g5-C5H5CH2CH2NH(CH3)-
Re(CO)3 (1) in tetrahydrofuran (THF) [6]. About
5–10% of N-hydroxybutyl complex 3d (Scheme 1) was
also isolated. Presumably, the photoexcitation of 1 gave
rise to an expulsion of a CO ligand. The resultant vacant
site was coordinated intramolecularly with the pendent
amino group to form the chelated complex 2, or stabi-
lized with the solvent to form the THF coordinated A.
The intermediate A could then undergo intramolecular
ligand exchange to give 2. Alternatively, under irradia-
tion condition, A could also undergo ring-opening of the
coordinated THF by the amino group intramolecularly
to give the minor compound 3d. Irradiation of the pu-
rified chelated complex 2 in THF also gave 3d, however,
in low yield along with decomposition. Various N-
substituted aminorhenium complexes 3a–3c were ob-
tained by deprotonation of the methylaminorhenium
complex 2 with n-butyllithium followed by alkylation
with alkyl halides (CH3I; C6H5CH2Br; n-C4H9Br)
[8,10]. The yellow solids of 3a–3d are stable at room
temperature under air.
Fig. 1. An ORTEP drawing of 3d.
Scheme 1.

T.-F. Wang et al. / Journal of Organometallic Chemistry 689 (2004) 411–418
413
2.2. Reaction with peroxy-acids
Examination of the crude 1H NMR spectra showed that
there are two sets of Cp protons and two well separated
N-methyl signals. The major component which the N-
methyl resonance appear at around d 2.8 was assigned to
the anti-isomer 4-anti (the g2-CO2 ligand and the bigger
substituent of the amino ligand are anti-orientation)
based upon the X-ray crystallographic analysis (see be-
low). Accordingly, the minor component that the N-
methyl resonance appears at around d 3.3 was assigned
to the syn-isomer 4-syn. The ratios were determined by
integration of the individual protons and are shown in
Table 1.
Single crystals of the major isomer 4d-anti from the
reaction of 3d with MCPBA were obtained from a so-
lution of CH2Cl2 and hexane. Fig. 2 shows the molec-
ular structure of 4d-anti. The CO2 ligand located at the
anti-position of the hydroxybutyl group along the Re–N
axis. The binding of the CO2 ligand to the metal is g2-
fashion with the O–C–O angle of 133°, similar to those
g2-CO2 complexes reported in the literature (124–134°)
[11]. It is worth noting that the core structures of 4d-anti
In general, low valent organometallic complexes are
vulnerable to oxidation. Therefore, we thought at be-
gining that the reaction of aminorhenium complex with
‘‘oxo’’ electrophiles might provide rheniumoxides or
messy complexes. To our surprise, addition of one
equivalent of MCPBA to a yellow solution of N,N-
dimethylaminorhenium complex 3a in CH2Cl2 at 0 °C
resulted in an immediate deepening of the color with the
disappearance of carbonyl absorptions of 3a (1899 and
1828 cmꢀ1) and the concomitant appearance of new
intense bands at 1873 and 1725 cmꢀ1 which are assigned
to the terminal carbonyl and g2-CO2 absorptions of the
carbon dioxide complex 4a. The structure had been
confirmed by X-ray crystallographic study to show that
the carbon dioxide ligand is coordinated to the rhenium
in a g2-fashion with the O–C–O angle of 131° [9].
Chiral complexes 3b–3d also reacted with MCPBA
smoothly to provide the corresponding g2-CO2 com-
plexes as a mixture of diastereomers (Scheme 2).
Scheme 2.
Table 1
The ratio of 4-anti:4-syn and yields in parenthesis for various reaction conditions
Reagents
4a
4b
4c
4d
MCPBA
MMPP
Br2/NaOH
(97)
(92)
18:1 (95)a
67:33 (96)
64:36 (95)
33:22:45 (70)b
70:30 (91)
63:37 (96)
39:38:23 (75)b
72:28 (98)
64:36 (75)
26:23:51 (45)b
a The ratio represents 4a:3a and the yield is the total isolated yield of 4a + 3a.
b The ratio represents 4-anti:4-syn:3 and the yield is the total isolated yield of 4 + 3.

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T.-F. Wang et al. / Journal of Organometallic Chemistry 689 (2004) 411–418
In addition to the homogeneous reaction with
MCPBA, the phase-transfer reaction (H2O/CH2Cl2) of 3
with the magnesium salt of monoperoxyphthalic acid
(MMPP) also provides 4 in good yield. The diastereo-
meric ratios and chemical yields (Table 1) are compa-
rable to those of the MCPBA reaction. Other peroxide
oxidants (t-BuOOH, H2O2, and O3) also gave carbon
dioxide complex 4, however, in only trace amount to-
gether with unidentifiable decomposition mixtures. Ox-
idation of the monomethylaminorhenium complex 2
gave decomposition or complex mixture only. Pure 4d-
anti compound does not isomerized to the correspond-
ing 4d-syn under the oxidation reaction condition and
the syn- and anti-isomers once formed the ratio stayed
unchanged, suggesting that the formation of 4-syn and
4-anti isomers are under kinetic control.
It is conceivable that the interaction of electron-rich
rhenium metal center with the electrophilic oxygen was
the first step for the reaction of aminorhenium complex
3 with peroxy-acid. The rhenium-oxo complex C was,
therefore, proposed as the transient intermediate which
then underwent intramolecular cyclization to give the
carbon dioxide complex.
Fig. 2. An ORTEP drawing of 4d-anti. There are two essentially in-
dependent molecules within the unit cell. Only one molecule is shown.
and the corresponding CO complex 3d are quite similar.
2.3. Bromination followed by base treatment
ꢀ
ꢀ
The bond lengths of Re–N (2.23 A for 3d and 2.20 A for
ꢀ
ꢀ
4d-anti) and Re–CO (1.88 A for 3d and 1.87 A for 4d-
anti), and the bond angles of N–Re–CO (97.6° for 3d
and 96.0° for 4d-anti) of both 3d and 4d-anti are very
close (see Table 2).
It has been reported that the bromination of
CpRe(CO)3 resulted in extrusion of a carbonyl ligand to
give the dibromo complex CpRe(CO)2Br2 [12]. Inter-
estingly, in the presence of electron donating amino
Table 2
ꢀ
Selected bond lengths (A) and angles (°) for 3d and 4d-anti
3d
4d-anti
Re1–N1
Re–N
2.232(4)
2.277(5)
2.247(5)
2.285(5)
1.876(5)
1.877(5)
1.521(6)
1.498(6)
1.481(7)
1.165(6)
1.165(7)
2.20(2)
2.26(2)
2.26(2)
2.32(2)
1.87(2)
2.01(2)
2.12(1)
1.45(3)
1.48(3)
1.19(2)
1.23(3)
Re–C3
Re–C6
Re–C7
Re–C13
Re–C14
N–C1
Re1–C3
Re1–C6
Re1–C7
Re1–C13
Re1–C14
Re1–O3
N1–C1
N–C8
N–C12
O13–C13
O14–C14
N1–C8
O1–C13
C14–O2
N–Re–C3
N–Re–C5
78.9(2)
135.1(2)
134.0(2)
97.5(2)
N1–Re1–C3
N1–Re1–C5
N1–Re1–C6
N1–Re1–C7
N1–Re1–C13
N1–Re1–C14
N1–Re1–O3
C3–Re1–C13
C3–Re1–C14
C3–Re1–O3
Re1–C13–O1
Re1–C14–O2
O2–C14–O3
78.9(6)
133.5(7)
132.6(8)
98.0(7)
96.0(7)
123.9(9)
88.0(6)
127.8(7)
137.6(8)
131.8(6)
178(2)
N–Re–C6
N–Re–C7
N–Re–C13
N–Re–C14
C3–Re–C13
C3–Re–C14
Re–C13–O13
Re–C14–O14
Re–N–C1
97.6(2)
100.1(2)
134.3(2)
136.0(2)
176.2(4)
174.3(5)
105.5(3)
115.6(3)
113.5(3)
Re–N–C8
Re–N–C12
151(2)
133(2)

T.-F. Wang et al. / Journal of Organometallic Chemistry 689 (2004) 411–418
415
Scheme 3.
ligand, bromination of aminorhenium complex 3a pro-
vides the corresponding cationic monobromo complex
5a without extrusion of any ligands (Scheme 3). The
symmetrical spectroscopic data (1H and 13C NMR)
suggest that 5a is a trans isomer. Graham and co-
workers [13] have reported that terminal carbonyl ligand
of cationic nitrosyl complex [CpRe(NO)(CO)2]þ reacts
with hydroxide ion to give the corresponding adduct
CpRe(NO)(CO)COOH, which upon loss of CO2 pro-
viding rhenium hydride complex CpRe(NO)(CO)H.
However, treatment of the CH2Cl2 solution of 5a with
aqueous sodium hydroxide provided the CO2 complex
4a (90%) together with a small amount of 3a (5%). The
reaction could be proceeding via the addition of hy-
droxide to one of the carbonyl ligand to give the cor-
responding carboxylic acid 6a, similar to that described
by Graham and co-workers [13]. In the basic reaction
condition, the carboxylic acid was deprotonated to give
presumably the carboxylate or g1-CO2 complex 7a [14],
whereupon the displacement of Brꢀ by the carboxylate
oxygen provided 4a. In the reaction, the initial Re(I) of
complex 3a was oxidized by bromine to Re(III). Upon
displacement of Brꢀ by the carboxylate, a formal re-
duction of Re(III) back to Re(I) took place intramo-
lecularly with concomitant formal oxidation of
carboxylate to carbon dioxide. It could not be ruled out
that the reaction proceeded with a CO2 expulsion, fol-
lowed by Brꢀ elimination and a recapture of CO2. The
formation of a small amount of 3a was resulted by the
hydroxide ion attacks on the Br ligand of complex 5a.
Reactions proceeded similarly for 3b–3d to provide a
mixture of anti- and syn-g2-CO2 complexes and recov-
ered 3. The ratios of anti- and syn-isomers are listed in
Table 1. Higher percentage of the recovery of 3b–3d
than that of 3a could be arising from the decreasing rate
of hydroxide ion attacked on the carbonyl ligand owing
to the bulkier substituent on the amino group. There-
fore, the relative rate of the hydroxide attacked on Br
ligand increases substantially and a significant amount
of recovered 3 resulted.
3. Experimental
General information has been reported previously
[8,15]. For the assignment of 1H and 13C NMR data, the
carbon bound to the nitrogen was designated as C1 and
the hydrogens on C1 were designated as H1a and H1b.
The next carbon was designated as C2, and the hydro-
gens on C2 were designated as H2a and H2b.
3.1. Preparation of g5:g1-C5H4CH2CH2NH(CH3)Re-
(CO)2 (2) and g5:g1-C5H4CH2CH2N(CH3)(n-BuOH)-
Re(CO)2 (3d)
Literature procedure [6] for the preparation of 2 was
followed, except that the more polar portion of 3d was
collected. That is, after irradiation of the complex 1
(6.326 g, 16.12 mmol) in THF (500 ml) at 0 °C for 2 h,
solvent was evaporated. The residue was chromato-
graphed on silica gel with 30% ethyl acetate in hexanes
as eluent followed by 50% and then 100% ethyl acetate.
The first yellow band (Rf ¼ 0:38, 30% EtOAc in hexane)
was collected and concentrated to give 3.78 g of 2 as
yellow powders (64% yield). The second yellow band at
Rf ¼ 0:18 (tailing, 50% EtOAc in hexane) was collected
and concentrated to give 0.452 g (6.6% yield) of 3d as
yellow powders. The physical data of 3d are recorded as
follows. M.p. 100–101 °C. IR (CH2Cl2): 1893, 1815
cmꢀ1. 1H NMR (CDCl3, 300 MHz): d 5.23–5.21 (1H, m,
Cp), 5.15–5.13 (1H, m, Cp), 4.91–4.89 (1H, m, Cp),
4.88–4.86 (1H, m, Cp), 3.73 (2H, t, J ¼ 6:1 Hz), 3.42–
3.26 (2H, m), 3.08 (1H, td, J ¼ 12:0, 4.0 Hz), 3.03 (3H, s,
N–CH3), 2.82 (1H, td, J ¼ 11:6, 5.2 Hz), 2.34 (1H, ddd,
J ¼ 14:6, 10.7, 5.7 Hz), 2.23–2.02 (2H, m), 1.94–1.79
(1H, m), 1.68–1.59 (2H, m). 13C NMR (CDCl3, 75

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T.-F. Wang et al. / Journal of Organometallic Chemistry 689 (2004) 411–418
MHz): d 205.8 (CO), 205.4 (CO), 119.8 (C, Cp), 82.4
(CH, Cp), 79.7 (CH2), 77.9 (CH, Cp), 76.0 (CH, Cp),
73.7 (CH, Cp), 73.2 (CH2), 62.0 (CH2), 58.4 (CH3), 29.7
(CH2), 25.1 (CH2), 24.4 (CH2). (Found: C, 38.49; H,
4.61; N, 3.42C14H20NO3Re requires: C, 38.52; H, 4.62;
N, 3.21.)
10.0, 5.5 Hz, H1a), 3.62 (1H, ddd, J ¼ 12:0, 5.4, 4.4 Hz,
H1b), 3.43 (3H, s, N–CH3), 2.89 (3H, s, N–CH3), 2.67
(1H, ddd, J ¼ 14:5, 10.0, 5.4 Hz, H2a), 2.47 (1H, ddd,
J ¼ 14:5, 5.5, 4.4 Hz, H2b). 13C NMR (C3D6O, 75
MHz): d 204.4 (CO), 182.2 (CO2), 126.6 (C, Cp), 93.1
(CH, Cp), 90.9 (CH, Cp), 79.3 (CH2), 77.0 (CH, Cp),
73.4 (CH, Cp), 61.5 (CH3), 52.1 (CH3), 25.9 (CH2).
(Found: C, 33.18; H, 3.29; N, 3.37%. C11H14NO3Re
requires: C, 33.50; H, 3.58; N, 3.55.)
3.2. Preparation of g5:g1-C5H4CH2CH2N(CH3)(n-Bu)-
Re(CO)2 (3c)
To a stirred solution of 2 (456 mg, 1.25 mmol) in
THF (10 ml) was added a hexane solution of n-BuLi (1.6
M, 0.95 ml, 1.5 mmol) over a period of 3 min at )78 °C.
After the solution was stirred for an additional 10 min,
n-BuBr (0.5 ml) was added. The cool bath was removed
and the solution stirred at room temperature for 30 min.
The residue after evaporation of solvents was chroma-
tographed on silica gel using 20% EtOAc in hexanes as
eluent. A yellow band at Rf ¼ 0:39 (20% EtOAc in
hexane) was collected and concentrated to give, after
recrystallization from a solution of CH2Cl2 and hexane,
0.358 g (68% yield) of 3c as yellow crystals. M.p. 101–
3.3.2. g5:g1-C5H4CH2CH2N(CH3)(CH2Ph)Re(CO)-
(g2-CO2) (4b)
96% yield (anti/syn: 67/33). The physical data were
recorded by using a mixture of anti- and syn-isomers.
M.p. 145–148 °C (decomp.). IR (CH2Cl2): 1873, 1727,
1112 cmꢀ1 1H NMR (C3D6O, 300 MHz, 4b-anti): d
.
7.52–7.23 (5H, m, Ph), 5.75–5.73 (1H, m, Cp), 5.52–5.50
(1H, m, Cp), 5.30–5.28 (1H, m, Cp), 5.14–5.12 (1H, m,
Cp), 4.93 (1H, d, J ¼ 13:4 Hz, benzylic-Ha), 4.72 (1H, d,
J ¼ 13:4 Hz, benzylic-Hb), 4.00 (1H, td, J ¼ 11:5, 5.7
Hz, H1a), 3.43 (1H, ddd, J ¼ 12:0, 5.2, 3.3 Hz, H1b), 2.78
(3H, s, N–CH3), 2.61 (1H, ddd, J ¼ 14.6, 11.0, 5.2 Hz,
102 °C. IR (CH2Cl2): 1895, 1818 cmꢀ1
.
1H NMR
1
H2a), 2.54–2.44 (1H, m, H2b). H NMR (C3D6O, 300
(CDCl3, 300 MHz): d 5.21–5.19 (1H, m, Cp), 5.15–5.13
(1H, m, Cp), 4.90–4.88 (1H, m, Cp), 4.87–4.85 (1H, m,
Cp), 3.41–3.29 (2H, m), 3.06 (1H, td, J ¼ 11:9, 4.2 Hz),
3.03 (3H, s), 2.80 (1H, td, J ¼ 11:6, 5.0 Hz), 2.32 (1H,
ddd, J ¼ 14:5, 10.4, 5.8 Hz), 2.18 (1H, ddd, J ¼ 14:5,
5.2, 3.4 Hz), 2.04–1.89 (1H, m), 1.73–1.60 (1H, m), 1.49–
1.29 (2H, m), 0.98 (3H, t, J ¼ 7:3 Hz). 13C NMR
(CDCl3, 75 MHz): d 205.9 (CO), 204.9 (CO), 119.5 (C,
Cp), 82.2 (CH, Cp), 79.6 (CH2), 77.9 (CH, Cp), 75.8
(CH, Cp), 73.6 (CH, Cp), 73.5 (CH2), 58.4 (CH3), 30.4
(CH2), 24.5 (CH2), 20.1 (CH2), 14.0 (CH3). (Found: C,
40.02; H, 4.68; N, 3.60%. C14H20NO2Re requires: C,
39.99; H, 4.79; N, 3.33.)
MHz, 4b-syn): d 7.52–7.23 (5H, m, Ph), 5.72–5.70 (1H,
m, Cp), 5.63–5.61 (1H, m, Cp), 5.35–5.33 (1H, m, Cp),
5.10–5.08 (1H, m, Cp), 4.45 (1H, d, J ¼ 13:4 Hz, ben-
zylic-Ha), 4.37 (1H, d, J ¼ 13:4 Hz, benzylic-Hb), 3.76–
3.59 (2H, m, H1Õs), 3.31 (3H, s, N–CH3), 2.90–2.82 (1H,
m, H2a), 2.54–2.44 (1H, m, H2b). 13C NMR (C3D6O, 75
MHz, 4b-anti): d 204.9 (CO), 182.2 (CO2), 133.6 (C, Ph),
133.1 (CH2, Ph), 130.1 (CH, Ph), 129.2 (CH x 2, Ph),
126.2 (C, Cp), 93.6 (CH, Cp), 90.7 (CH, Cp), 76.3 (CH,
Cp), 75.8 (CH, Cp), 73.5 (CH2), 56.6 (CH3), 46.9 (CH2),
25.7 (CH2). (Found: C, 43.18; H, 3.88; N, 3.14%.
C17H18NO3Re requires: C, 43.39; H, 3.86; N, 2.98.)
3.3. Reaction of 3a–d with m-chloroperoxybenzoic acid.
Preparation of g5:g1-C5H4CH2CH2NR(CH3)Re(CO)-
(g2-CO2) (4a–d; R ¼ methyl, benzyl, n-butyl, n-butyl-
OH)
3.3.3. g5:g1-C5H4CH2CH2N(CH3)(n-C4H9)Re(CO)-
(g2-CO2) (4c)
91% yield (anti/syn: 70/30). The physical data were
recorded by using a mixture of anti- and syn-isomers.
M.p. 143–145 °C (decomp.). IR (CH2Cl2): 1873, 1728,
To a stirred solution of 3a–d (1 mmol) in CH2Cl2 (20
ml) at 0 °C was added MCPBA (237 mg, 80%, 1.1
mmol). The yellow color of the solution turned deeper
immediately. After stirring for 20 min, CH2Cl2 was
evaporated. The residual solids were washed three times
with diethyl ether to give analytically pure 4a–d as yel-
low powders.
1122 cmꢀ1 1H NMR (C3D6O, 300 MHz, 4c-anti): d
.
5.62–5.60 (1H, m, Cp), 5.51–5.49 (1H, m, Cp), 5.25–5.23
(1H, m, Cp), 5.10–5.08 (1H, m, Cp), 3.84 (1H, td,
J ¼ 12:2, 5.5 Hz, H1a), 3.59 (1H, ddd, J ¼ 12:2, 5.4, 1.4
Hz, H1b), 3.41–3.18 (2H, m), 2.89–2.76 (1H, m), 2.84
(3H, s, N–CH3), 2.36 (1H, dd, J ¼ 14.5, 5.5 Hz), 1.87–
1.60 (2H, m), 1.47–1.25 (2H, m), 0.89 (3H, t, J ¼ 7:4
Hz). 1H NMR (C3D6O, 300 MHz, 4c-syn, partial): d
5.70–5.68 (1H, m, Cp), 5.51–5.49 (1H, m, Cp), 5.35–5.33
(1H, m, Cp), 5.10–5.08 (1H, m, Cp), 3.33 (3H, s, N–
CH3). 13C NMR (C3D6O, 75 MHz, 4c-anti): d 204.3
(CO), 183.0 (CO2), 126.2 (C, Cp), 93.9 (CH, Cp), 90.0
(CH, Cp), 77.4 (CH2), 75.1 (CH, Cp), 74.0 (CH, Cp),
73.0 (CH2), 47.4 (CH3), 29.6 (CH2), 25.4 (CH2), 20.7
3.3.1. g5:g1-C5H4CH2CH2N(CH3)2Re(CO)(g2-CO2)
(4a)
97% yield. M.p. 160–165 °C. IR (CH2Cl2): 1873,
1725, 1120 cmꢀ1. 1H NMR (C3D6O, 300 MHz): d 5.69–
5.67 (1H, m, Cp), 5.48–5.46 (1H, m, Cp), 5.29–5.27 (1H,
m, Cp), 5.08–5.06 (1H, m, Cp), 3.90 (1H, ddd, J ¼ 12:0,

T.-F. Wang et al. / Journal of Organometallic Chemistry 689 (2004) 411–418
417
(CH2), 14.2 (CH3). (Found: C, 38.50; H, 4.71; N, 3.35%.
C14H20NO3Re requires: C, 38.52; H, 4.62; N, 3.21.)
3.6. Crystal structure of g5:g1-C5H4CH2CH2N(CH3)
(n-C4H8OH)Re(CO)2(3d) and g5:g1-C5H4CH2CH2N-
(CH3)(n-C4H8OH)Re(CO)(g2-CO2) (4d-anti)
3.3.4. g5:g1-C5H4CH2CH2N(CH3)(n-C4H8OH)Re(CO)
(g2-CO2) (4d)
98% yield (anti/syn: 72/28). The physical data were
Single crystals of 3d and 4d-anti were obtained by slow
diffusion of each individual CH2Cl2 solution into hexane
at room temperature. Diffraction measurements were
made on an Enraf-Nonius CAD-4 automated diffrac-
tometer by use of a graphite-monochromated Mo Ka
recorded by using a mixture of anti- and syn-isomers.
M.p. 120–125 °C. IR (CH2Cl2): 1873, 1728, 1122 cmꢀ1
.
1H NMR (C3D6O, 300 MHz, 4d-anti): d 5.60–5.58 (1H,
m, Cp), 5.49–5.47 (1H, m, Cp), 5.23–5.21 (1H, m, Cp),
5.11–5.09 (1H, m, Cp), 3.85 (1H, td, J ¼ 12:2, 5.6 Hz,
H1a), 3.62–3.50 (2H, m), 3.43–3.27 (2H, m), 2.84 (3H, s,
N–CH3), 2.84–2.75 (2H, m), 2.37 (1H, ddd, J ¼ 14:4,
ꢀ
radiation (k ¼ 0:710 69 A) with h–2h scan mode. The unit
cells were determined and refined using 25 randomly se-
lected reflections obtained with the automatic search,
center, index, and least-squares routines. Lorentz/polar-
ization and empirical absorption corrections based on
three azimuthal scans were applied to the data. The space
1
5.5, 1.4 Hz), 1.88–1.78 (2H, m), 1.56–1.46 (2H, m). H
NMR (C3D6O, 300 MHz, 4d-syn, partial): d 5.69–5.67
(1H, m, Cp), 5.49–5.47 (1H, m, Cp), 5.34–5.32 (1H, m,
Cp), 5.09–5.07 (1H, m, Cp), 3.34 (3H, s, N–CH3). 13C
NMR (C3D6O, 75 MHz, 4d-anti): d 204.5 (CO), 181.8
(CO2), 125.9 (C, Cp), 93.8 (CH, Cp), 90.0 (CH, Cp),
77.3 (CH2), 75.0 (CH, Cp), 74.1 (CH, Cp), 73.2 (CH2),
60.1 (CH2), 47.2 (CH3), 31.0 (CH2), 25.4 (CH2), 24.4
(CH2). (Found: C, 37.19; H, 4.38; N, 3.02%. C14H20
NO4Re requires C, 37.16; H, 4.45; N, 3.10.)
ꢁ
groups (P1 for 3d and Pbn21 for 4d-anti) were determined
from the systematic absences observed during data col-
lection. All data reduction and refinements were carried
out on a DecAlpha 3400/400 computer using the NRCVX
program [16]. The structures were solved by direct
methods and refined by a full-matrix least-squares rou-
tine [17] with anisotropic thermal parameters for all
non-hydrogen atoms. The structures were refined by
wjFo ꢀ Fc2j, where w ¼ ð1=r2ÞFo was cal-
P
minimizing
3.4. Two phase reactions of 3 with magnesium monop-
eroxyphthalate (MMPP)
Table 3
Crystallographic data and structure refinements for 3d and 4d-anti
Compound
3d
4d-anti
To a stirred solution of 3a–d (0.5 mmol) in CH2Cl2
(10 ml) at 0 °C was added a water solution of MMPP (2
ml, 0.3M). The yellow color of the CH2Cl2 layer turned
deeper immediately. After stirring for 20 min, CH2Cl2
layer was separated and evaporated. The residual solids
were washed three times with diethyl ether to give 4a–d
as yellow powders. See Table 1 for yields and the anti to
syn ratios.
Formula
C14H20NO3Re
436.52
C14H20NO4Re
452.52
Formula weight
Crystal size (mm)
Color
0.41 ꢁ 0.19 ꢁ 0.38
yellow
293
0.30 ꢁ 0.18 ꢁ 0.16
orange
293
Temperature (K)
Crystal system
Space group
triclinic
ꢁ
orthorhombic
Pbn21
8.4343(14)
15.989(2)
21.802(4)
90
P1
ꢀ
a (A)
7.4028(7)
8.2371(15)
12.879(3)
94.231(17)
90.694(15)
114.564(13)
711.5(2)
2
ꢀ
b (A)
ꢀ
c (A)
3.5. Preparation of {[g5:g1-C5H4CH2CH2N(CH3)2]Re-
(CO)2Br}þBrꢀ (5a)
a (°)
b (°)
c (°)
90
90
3
ꢀ
V (A )
2940.1(8)
8
2.036
To a stirred solution of 3a (175 mg, 0.46 mmol) and
pyridine (0.05 mL) in CH2Cl2 (30 ml) at 0 °C was added
a solution of bromine in CH2Cl2 (0.5 M, 1.2 ml) slowly
over 5 min. After stirring for another 20 min, the yellow
powders were collected and washed once with a small
amount of CH2Cl2. Evaporation under reduced pressure
gave 210 mg (85% yield) of 5a as yellow powders. M.p.
92–95 °C (decomp.). IR (CH3OH): 2064, 2001 cmꢀ1. 1H
NMR (CD3OD, 300 MHz): d 7.14 (2H, t, J ¼ 2 Hz, Cp
H), 5.80 (2H, t, J ¼ 2 Hz, Cp H), 4.05 (2H, t, J ¼ 6:4
Hz, H1Õs), 3.48 (6H, s), 2.61 (2H, t, J ¼ 6:4 Hz, H2Õs).
13C NMR (CD3OD, 75 MHz): d 192.2 (CO 2ꢁ), 133.6
(C, Cp), 97.2 (CH 2ꢁ, Cp), 93.9 (CH 2ꢁ, Cp), 88.9
(CH2, C1), 64.5 (CH3 2ꢁ), 25.4 (CH2, C2). (Found: C,
24.60; H, 2.92; N, 2.96%. C11H14Br2NO2Re requires: C,
24.55; H, 2.62; N, 2.60.)
Z
Dc (g cmꢀ3
F ð000Þ
)
2.038
418
1736
0.71069
82.75
ꢀ
k(Mo Ka) (A)
l(Mo Ka) (cmꢀ1
Tmin;max
0.71069
86.585
)
0.453, 1.00
0.824–2.06
0:80 þ 0:35 tan h
50
0.50, 1.00
0.824–2.747
0:75 þ 0:35 tan h
45
Scan rate (deg minꢀ1
h/2h scan width (°)
2hmax (°)
)
h; k; l range
(ꢀ8; 7), (0; 9),
(ꢀ15; 15)
2498
(0; 9), (0; 17),
(0; 23)
1973
Unique reflections
Observed reflections
(I > 2:0rðIÞ)
Refined parameters
R; wR
2345
1728
173
0.020; 0.026
1.69
360
0.0320; 0.0803
1.024
S
ꢀ3
ꢀ
(Dq)max;min (e A
)
0.930; )0.890
1.813; )1.343

418
T.-F. Wang et al. / Journal of Organometallic Chemistry 689 (2004) 411–418
[3] (a) M. Aresta, C.F. Nobile, J. Chem. Soc., Dalton Trans. (1977)
708;
culated from the counting statistics. Hydrogens were in-
cluded in the structure factor calculations in their ex-
pected positions on the basis of idealized bonding
geometry but not refined in least-squares. The final cell
parameters and data collection parameters are listed in
Table 3. The ORTEP drawings are shown in Fig. 1 for 3d
and Fig. 2 for 4d-anti.
(b) M. Aresta, C.F. Nobile, J. Chem. Soc., Chem. Commun.
(1975) 636.
[4] S. Komiya, M. Akita, N. Kasuga, M. Hirano, A. Fukuoka,
J. Chem. Soc., Chem. Commun. (1994) 1115.
[5] P.-F. Fu, M.A. Khan, K.M. Nicholas, J. Am. Chem. Soc. 114
(1992) 6579.
[6] P.-F. Fu, A.K. Fazlur-Rahman, K.M. Nicholas, Organometallics
13 (1994) 413.
[7] (a) D.H. Gibson, Chem. Rev. 96 (1996) 2063;
(b) W. Leitner, Coord. Chem. Rev. 153 (1996) 257.
[8] T.-F. Wang, C.-Y. Lai, C.-C. Hwu, Y.-S. Wen, Organometallics
16 (1997) 1218.
4. Conclusion
We have demonstrated that the aminorhenium carbon
dioxide complex could be easily obtained from the cor-
responding carbonyl complex via a formal oxidation of
the carbon monoxide ligand. The diastereoselectivity of
the resultant g2-CO2 complex is predominantly the anti-
isomer. Two approaches for the formation of CO2
complexes from the corresponding CO complexes have
been realized. The peroxy-acids (MCPBA and MMPP)
methodology provided direct access to the high yielded
CO2 complexes. The two steps approach, bromination
followed by hydroxide treatment, gave us a clearer pic-
ture of the reaction pathway on the formation of CO2
complexes. The presence of the electron donating amino
ligand may be an important factor for the preparation of
CO2 complexes been successful. In the course of oxida-
tion, the amino ligand stabilized the developing positive
charge, thereby allowing the subsequent transformations
proceeded smoothly to give the CO2 complex.
[9] A preliminary communication has been reported: T.-F. Wang,
C.-C. Hwu, C.-W. Tsai, K.-J. Lin, Organometallics 16 (1997)
3089.
[10] The dimethylamino complex 3a has also been synthesized from the
irradiation of g5-C5H5CH2CH2N(CH3)2Re(CO)3 in THF, see:
T.-F. Wang, J.-P. Juang, K.-J. Lin, Bull. Inst. Chem., Acad. Sin.
42 (1995) 41.
[11] (a) G.S. Bristow, P.B. Hitchcock, M.F. Lappert, J. Chem. Soc.,
Chem. Commun. (1981) 1145;
(b) R. Alvarez, E. Carmona, E. Gutierrez-Puebla, J.M. Marin, A.
Monge, M.L. Poveda, J. Chem. Soc., Chem. Commun. (1984)
1326;
(c) S. Komiya, M. Akita, N. Kasuga, M. Hirano, A. Fukuoka,
J. Chem. Soc., Chem. Commun. (1994) 1115;
(d) S. Gambarotta, C. Floriani, A. Chiesi-Villa, C. Guastini,
J. Am. Chem. Soc. 107 (1985) 2985.
[12] (a) R.B. King, R.H. Reimann, Inorg. Chem. 15 (1976) 179;
(b) L. Cheng, N.J. Coville, Organometallics 15 (1996) 867.
[13] (a) J.R. Sweet, W.A.G. Graham, Organometallics 1 (1982)
982;
(b) For reactions using phase-transfer catalysis see: H. Alper,
Adv. Organomet. Chem. 19 (1981) 183;
(c) D.H. Gibson, W.L. Hsu, D.S. Lin, J. Organomet. Chem.
172 (1979) C7.
Acknowledgements
[14] (a) J.C. Calabrese, T. Herskovitz, J.B. Kinney, J. Am. Chem. Soc.
105 (1983) 5914;
We are grateful to the National Science Council of
Taiwan for financial support.
(b) H. Tanaka, H. Nagao, S.-M. Peng, K. Tanaka, Organomet-
allics 11 (1992) 1450.
[15] T.F. Wang, C.C. Hwu, C.W. Tsai, Y.S. Wen, J. Chem. Soc.,
Dalton Trans. (1998) 2091.
[16] E.J. Gabe, Y. LePage, J.P. Charland, F.L. Lee, P.S. White,
J. Appl. Crystallogr. 22 (1989) 384.
References
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1985, pp. 206–215.
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(b) W. Leitner, Coord. Chem. Rev. 153 (1996) 257.