Cyrhetrenylimines and cyrhetrenylamines: Synthesis, characterization and X-ray crystal structure

Article abstract of DOI:10.1016/j.poly.2008.04.021

Cyrhetrenyl Schiff base derivatives of the form (η⁵-C₅H₄CH{double bond, long}NAr)Re(CO)₃, [Ar = Ph (1a) C₆H₄OMe-p (1b) and C₆H₄NO₂-p (1c)] have been prepare

Full text of DOI:10.1016/j.poly.2008.04.021

Polyhedron 27 (2008) 2421–2425
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Cyrhetrenylimines and cyrhetrenylamines: Synthesis, characterization
and X-ray crystal structure
Rodrigo Arancibia a, Fernando Godoy a, Gonzalo E. Buono-Core a, A. Hugo Klahn a,
,
*
Enrique Gutierrez-Puebla b, Angeles Monge b
a Instituto de Quimica, Pontificia Universidad Catolica de Valparaíso, Casilla 4059, Valparaíso, Chile
b Instituto de Ciencias de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain
a r t i c l e i n f o
a b s t r a c t
Cyrhetrenyl Schiff base derivatives of the form (g5-C5H4CH@NAr)Re(CO)3, [Ar = Ph (1a) C6H4OMe-p (1b)
and C6H4NO2-p (1c)] have been prepared from cyrhetrenylcarbaldehyde and the corresponding aromatic
amines. 1H and 13C NMR indicates that these compounds have the anti-(E) conformation in solution and
the X-ray crystal structure of 1b confirms that it also adopts the anti-(E) form in the solid state. Further
reaction of cyrhetrenylaldimines 1 with sodium borohydride in methanol produces quantitatively, the
corresponding amine derivatives (g5-C5H4CH2–NHAr)Re(CO)3 [Ar = Ph (2a) C6H4OMe-p (2b) and
C6H4NO2-p (2c)]. All these cyrhetrenylamines were characterized by IR, 1H and 13C NMR, MS. Addition-
ally, 2b has been characterized structurally.
Article history:
Received 27 December 2007
Accepted 21 April 2008
Available online 2 June 2008
Keywords:
Cyrhetrenyl Schiff bases
Reduction
Cyrhetrenylamines
X-ray characterization
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
would like to report the synthesis and characterization of the
cyrhetrenylimine (Schiff base) complexes (g5-C5H4CH@NAr)Re-
Ferrocenylimines (g5-C5H5)Fe(g5–C5H4CR@NAr) and ferroce-
nylamines (g5-C5H5)Fe(g5-C5H4CHRNHAr), R = H, Me, Ph; and
Ar = a variety of substituted phenyl, have attracted a great deal of
attention in the past two decade due to their wide application in
molecular materials [1], bioorganometallic chemistry [2] and as li-
gands capable of coordinating transition metal ions giving com-
plexes with potential applications in catalysis [3]. The above
situation contrasts with the smaller number of analogous com-
pounds bearing the cyrhetrenyl group (g5-C5H4)Re(CO)3, described
in the literature. To our best knowledge the only known cyrhetre-
nylimine (g5-C5H4CH@NPh)Re(CO)3, was briefly described by
Kolobova et al. [4,5]. More recently, complexes of these type have
been used in situ, as intermediates for the preparation of some bio-
logical compounds containing the (g5-C5H4)Re(CO)3 group (see be-
low) but details of their isolation and characterization remain
unknown [6]. On the other hand, reduction of ferrocenylimines
with sodium borohydride or lithium aluminium hydride has been
shown to be an efficient procedure for the preparation of (N-aryl)-
amino methylferrocenes. A similar approach have been used by
Jaouen to prepare poly(amidoamine) dendrimers tethered with
cyclopentadienyl rhenium tricarbonyl [6]. As part of our interest
in comparing the properties of the cyrhetrenyl substituted systems
with the well known analogous ferrocenyl [7], in this paper we
(CO)3, and the cyrhetrenyl-amine derivatives (g5-C5H4CH2–NHAr)-
Re(CO)3. The imine and amine complexes derived from p-anisidine
were also studied X-ray crystallography.
2. Results and discussion
2.1. Cyrhetrenylimine complexes (g5-C5H4CH@NAr)Re(CO)3 (1)
The Schiff bases (g5-C5H4CH@NAr)Re(CO)3, Ar = Ph (1a)
C6H4OMe-p (1b) and C6H4NO2-p (1c) were synthesized following
the same procedure to that described for analogous ferrocenyli-
mines derivatives [8], that is by condensation of the corresponding
aniline with formylcyrhetrene (g5-C5H4COH)Re(CO)3 [9] (Scheme
1).
The procedure consists of the reaction of equimolar amounts of
formylcyrhetrene and the aromatic amine in refluxing toluene. A
Dean–Stark apparatus was used to remove the toluene–water
azeotrope formed during the reaction formation of 1c. In all cases
the products were isolated as white crystalline solids after crystal-
lization from CH2Cl2-hexane mixture (1:5).
The IR spectra of these compounds showed the expected value
of the mC@N stretch in the range 1625–1643 cmÀ1, in CH2Cl2 solu-
tion. This absorption bands as well as the mCO of the carbonyls
bound to rhenium are shifted to lower wavenumber when com-
pared to the precursor formylcyrhetrene [9]. Similar mC@N fre-
quency shifts have been reported for Schiff bases derived from
* Corresponding author. Tel.: +56 32 2273174; fax: +56 32 2273422.
E-mail address: hklahn@ucv.cl (A. Hugo Klahn).
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.04.021

2422
R. Arancibia et al. / Polyhedron 27 (2008) 2421–2425
Table 1
O
H
Crystal data and structure refinement for 1b and 2b
C-H
C
N-Ar
Compound
1b
2b
+
H2O
Re
NH2-Ar
+
Re
Empirical Formula
Formula weight
Temperature (K)
wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
a (°)
b (°)
C
16H12NO4Re
C16H14NO4Re
470.47
295(2)
C
O
C
C
C
468.47
295(2)
0.71073
monoclinic
P2(1)/n
C
O
C
O
O
O
O
0.71073
triclinic
1a, Ar = C6H5
1b, Ar = C6H4-p-OCH3
1c, Ar = C6H4-p-NO2
ꢀ
P1
11.2762(5)
8.3746(4)
16.1881(7)
90
93.2030(10)
90
1526.31(12)
4
2.039
7.4071(5)
7.9042(6)
13.8307(10)
89.3360(10)
86.6540(10)
78.6150(10)
792.46(10)
2
1.967
7.683
446
0.30 Â 0.20 Â 0.20
2.63–29.16
À9 6 h 6 9,
À10 6 k 6 10,
À18 6 l 6 18
7576
Scheme 1.
formylferrocene [8]. Each of 1a–c showed a strong molecular ion
and fragments corresponding to the successive lost of three CO,
in their mass spectra.
c (°)
Volume (Å3)
Z
The 1H NMR spectra showed a singlet at about d 8.0 due to the
iminic proton and two apparent triplets between 5.42 and
6.07 ppm. The latter are ascribed to the monosubstituted cyclopen-
tadienyl ring. In addition, resonances for the hydrogen atoms of the
aryl ring and the methoxy substituent were also observed. 13C
NMR data were also in accordance with the existence of a single
compound. Despite the fact that these type of compounds could
adopt two different forms (E- or Z-) [1b,3c,10] their 1H and 13C
NMR spectra, which agreed with those reported for related ferroce-
nyl Schiff bases [1b,3c,10], revealed that only one isomer (E-form)
was present in solution. Further proof was provided by an X-ray
crystal structure determination of 1b (see below). The most impor-
tant feature of these spectra is the presence of a low field reso-
nance (d 152–158) assigned to the iminyl carbon. This resonance
occurs at almost the same d as those reported for the ferrocene
analogues [1,3c,10] and is indicative of some degree of conjugation
of the C5H4 ring and the –HC@N entity.
Dcalc (g/cm3)
Absorption coefficient (mmÀ1
F(000)
)
7.978
888
Crystal size (mm)
h Range for data collection (°)
Index ranges
0.30 Â 0.20 Â 0.20
2.15–29.05
À15 6 h 6 15,
À11 6 k 6 11,
À20 6 l 6 21
13557
Reflections collected
Independent reflections (Rint
Completeness to
theta = 29.05° (%)
Absorption correction
)
3786 (0.0377)
92.7
3776 (0.0269)
88.6
empirical
empirical
Refinement method
full-matrix least-
squares on F2
3786/0/236
1.127
R1 = 0.0373,
wR2 = 0.0622
R1 = 0.0550,
wR2 = 0.0659
0.983 and À1.233
full-matrix least-
squares on F2
3776/0/251
1.053
R1 = 0.0262,
wR2 = 0.0585
R1 = 0.0314,
wR2 = 0.0600
0.769 and À0.905
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
With the aim to compare structural parameters of these com-
pounds with the crystallographic data reported for several ferroce-
nylimines [1a,8c,10,11], we undertook a crystallographic study of
complex 1b. The structure of 1b is shown in Fig. 1. Table 1 reports
the crystal structure and refinement data and Table 2 shows se-
lected bond lengths and angles. The structure confirms the E con-
figuration assigned tentatively by NMR. Taking into account the
internal and exocyclic C–C distances of the cyclopentadienyl ring
and the classification done for substituted ferrocene derivatives
[1a,10], a fulvenoid type of structure can be considered for 1b,
since it possesses alternated two short and three long C–C dis-
tances (C(2)–C(3) 1.403 Å; C(4)–C(5) 1.402 Å; C(1)–C(2) 1.446 Å;
C(1)–C(5) 1.412 Å and C(3)–C(4) 1.433 Å), and the exocyclic C(1)–
C(9) of 1.456 Å. Additional support for this assignment is to be
found in the C@N bond length (1.265 Å), which is within the range
to those measured in several ferrocenyl Schiff bases [1a,8c,10,11],
and the C5H4CH@N part of the molecule are practically flat, the
maxima deviation from the least-squares plane formed by the
atoms of the C5 ring and C(9), N(1) and C(10) atoms is only 0.1 Å.
This is in agreement with the suggestion that some delocalization
Largest difference in peak and
hole (e ÅÀ3
)
of electron density is found over the C5H4CH@N moiety. On the
other hand, within the cyrhetrenyl group, the average Re–C(O) dis-
tance and the Re–C–O angle are concordant with related tricar-
bonyl cyclopentadienyl rhenium(I) complexes [7].
2.2. Cyrhetrenylamine complexes (g5-C5H4CH2NHAr)Re(CO)3 (2)
These compounds were prepared according to the general pro-
cedure described for most ferrocenylamines [3f,11] that is, by
direct reduction of the corresponding cyrhetrenyl imine complex
1 with NaBH4 in anhydrous methanol, at room temperature
(Scheme 2).
Table 2
Select bond lengths (Å), bond angles and dihedral angles (°) for 1b and 2b
Compound
1b
2b
Bond lengths (Å)
C(1)–C(9)
C(9)–N(1)
N(1)–C(10)
Cp(centroid)–Re(1)
Re–C(CO) av.
1.456(7)
1.265(7)
1.414(6)
1.961(6)
1.923
1.511(5)
1.454(5)
1.414(5)
1.949(5)
1.904
Bond angles (°)
N(1)–C(9)–C(1)
C(9)–N(1)–C(10)
C(13)–O(4)–C(16)
OC–Re–CO av.
121.8(5)
119.5(5)
116.3(5)
89.57
113.1(3)
119.9(3)
117.3(4)
90.18
Fig. 1. Molecular structure of cyrhetrenylimine 1b.

R. Arancibia et al. / Polyhedron 27 (2008) 2421–2425
2423
and the Re–C–O angles are concordant with the corresponding val-
ues reported for substituted-cyclopentadienyl tricarbonyl rhe-
nium(I) complexes [7,15].
H
C
N-Ar
CH2-NH-Ar
NaBH4
MeOH
Re
Re
C
C
C
C
O
C
O
C
O
3. Experimental
O
O
O
(g5-C5H4CHO)Re(CO)3 was prepared according to the literature
method [9]. Anilines and NaBH4 were obtained commercially (Al-
drich). All the solvents were purified according standard methods
prior to use. Infrared spectra were recorded in solution (NaCl cell)
2a, Ar = C6H5
2b, Ar = C6H4-p-OCH3
2c, Ar = C6H4-p-NO2
Scheme 2.
on a Perkin–Elmer FT-1605 spectrophotometer, and the 1H and 13
C
NMR spectra were measured on a Bruker AVANCE 400 spectrome-
ter. 1H NMR chemical shifts were referenced using the chemicals
shifts of residual solvent resonances, and 13C chemical shifts to sol-
vent peaks. Mass spectra were obtained on a Thermo-Finnigan
MAT 900XP, at the Facultad de Ciencias Químicas y Farmacéuticas,
Universidad de Chile.
The products were purified by column chromatography and iso-
lated in quantitative yields as white solids. The IR spectra, in
CH2Cl2 solution, showed as expected, the presence of two mCO
bands, which are slightly shifted to lower wavenumber compared
to their parent complexes 1. In addition to the resonances of the
cyclopentadienyl and aryl groups, in all cases the 1H NMR spectra,
in C6D6 solution, clearly showed at d ꢀ 3.4, a doublet and a broad
singlet for the CH2 and NH groups, respectively. These assignments
were confirmed by 1H–1H NMR COSY.
3.1. (g5-C5H4CH@NC6H5)Re(CO)3 (1a)
To a solution of (g5-C5H4CHO)Re(CO)3 (50.0 mg, 0.138 mmol) in
toluene (15 mL) was added 1.25 mL (0.138 mmol) of a 0.110 M ani-
line solution in toluene. The mixture was refluxed for 15 h. After
this time, an IR spectrum of the solution showed the complete dis-
appearance of the cyrhetrenylcarboxaldehyde complex (2033s;
1940s and 1694 cmÀ1) and the presence of the new CO absorptions
due to 1a. The solvent was pumped off and the solid crystallized
from CH2Cl2/hexane at À18 °C to give white crystals of 1a (yield:
58.0 mg, 0.132 mmol, 95.7%). IR (CH2Cl2, cmÀ1) 2026s, (mCO);
1934s, (mCO); 1630w, (mC@N). 1H NMR (CDCl3) d: 5.44 (t,
J = 2.4 Hz, 2H,C5H4); 6.00 (t, J = 2.4 Hz, 2H, C5H5); 7.09 (m, 2H,
C6H5); 7.23 (t, J = 7.4, 1H, C6H5); 7.37 (t, J = 7.8, 2H, C6H5); 8.07 (s,
1H, CH@N). 13C NMR (CDCl3) d: 84.9 (C5H4); 86.0 (C5H4); 99.5 (s,
The main feature of the 13C NMR spectrum of each compound,
in CDCl3 solution, is a resonance at about 41 ppm which has been
assigned to the CH2 group on the basis of the reported chemical
shifts for the methylene group in analogous ferrocenylamines
[12,13]. The resonances of CO groups (Re–CO) occurred to similar
chemical shift to others tricarbonyl cyclopententadienyl function-
alized complexes [7,9].
The mass spectra of 2a–c exhibited the molecular ion, and the
successive loss of three CO ligands. In all cases, the most intense
peak corresponds to the elimination of the amine fragment (NHAr)
to give cyrhetrenylmetylene cation (m/z 349, 100%). This fragmen-
tation is similar to that observed for the complex (g5-
C5H4CH2NHC6H5)Fe(g5-C5H5) [12,13].
Cipso, C5H4); 120.6 (s, C6H4); 126.3 (s, C6H4); 129.2 (s, C6H4); 151.0
(s, C6H4); 152.1 (CH@N); 192.7 (CO). Mass spectrum (based on
187Re) m/z 439 [M+], 411 [M+ÀCO], 383 [M+À2CO], 355
[M+À3CO]. Anal. Calc. for C15H10O3NRe: C, 41.09; H, 2.28. Found:
C, 42.02; H, 2.31%.
The elementals analyses are in a good agreement with the pro-
posed structures.
The molecular structure of amine 2b (Fig. 2) shows no signifi-
cant differences in bond lengths and angles (Table 1) when
compared to the structure of the ferrocene related compounds
[12–14]. The torsion angle C(10)–N–C(9)–C(1) of 59.0° indicates a
Syn-Clinal arrangement of the substituents at the N–C(9) bond.
The angle 81.6° between the planes of the Cp ring with the aro-
matic ring is almost orthogonal. On the other hand, the rhenium-
ring centroid distance 1.949 (5) Å, the average Re–C(O) distance
3.2. (g5-C5H4CH@NC6H4OCH3-p)Re(CO)3 (1b)
To a solution of (g5-C5H4CHO)Re(CO)3 50.0 mg (0.138 mmol) in
toluene (10 mL) was added p-anisidine 17.0 mg (0.138 mmol). The
mixture was refluxed under nitrogen atmosphere for 5 h. After this
time, the solution changed color from yellow to brown. The IR
spectrum showed the complete disappearance of the starting com-
plex and three new absorption bands. The solvent was removed
under vacuum and a gray oil was obtained. Crystallization from
CH2Cl2/hexane (1:5) at À18 °C to give off-white microcrystals of
1b (Yield: 61 mg, 0.130 mmol, 94.4%). IR (CH2Cl2, cmÀ1): 2026s,
(mCO), 1932s, (mCO), 1627w, (mC@N). 1H NMR (CDCl3): d: 3.81 (s,
3H, OCH3); 5.42 (t, J = 2.4 Hz, 2H, C5H4); 5.96 (t, J = 2.4 Hz, 2H,
C5H4); 6.90 (pseudo-dt, 2H, C6H4); 7.11 (pseudo-dt, 2H, C6H4);
8.08 (s,1H, CH@N). 13C NMR (CDCl3): d: 55.5 (s, OCH3); 84.8
(C5H4); 85.7 (C5H4); 100.2 (s, C5H4); 114.4 (s, C6H4); 122.0 (s,
C6H4); 143.8 (s, C6H4); 150.0 (s, C6H4); 158.54 (CH@N), 192.86
(CO). Mass spectrum (based on 187Re) m/z: 469 [M+], 441
[M+ÀCO], 413 [M+À2CO], 385 [M+À3CO]. Anal. Calc. for
C16H12O4NRe: C, 41.02; H, 2.58. Found: C, 42.13; H, 2.64%.
3.3. (g5-C5H4CH@NC6H4NO2-p)Re(CO)3 (1c)
The synthesis of the complex 1c was carried out in a similar
manner to that described for complex 1b using (g5-C5H4CHO)Re-
(CO)3 (50.0 mg, 0.138 mmol) and p-nitroaniline (19.0 mg, 0.138 mmol)
but refluxing for 48 h using a Dean–Stark apparatus. 1c was
Fig. 2. Molecular structure of cyrhetrenylamine 2b.

2424
R. Arancibia et al. / Polyhedron 27 (2008) 2421–2425
obtained as white-yellow crystals (Yield: 61, 0.126 mmol, mg,
91.3%). IR (CH2Cl2, cmÀ1) 2028s (mCO), 1936s (mCO), 1625w (mC@N).
1H NMR (CDCl3) d: 5.49 (t, J = 2.0 Hz, 2H,C5H4), 6.03 (t, J = 2.0 Hz,
2H, C5H4), 7.13 (pseudo-dt, 2H, C6H4); 8.08 (s, 1H, CH@N); 8.24
(pseudo-dt, 2H, C6H4); 13C NMR (CDCl3): d 85.4 (C5H4); 86.8
(C5H4); 97.5 (s, C5H4); 111.3 (s, C6H4); 121.1 (s, C6H4); 125.0 (s,
C6H4); 126.3 (s, C6H4); 156.7 (CH@N), 192.86 (CO). Mass spectrum
(based on 187Re) m/z: 484 [M+], 456 [M+ÀCO], 428 [M+À2CO], 400
[M+À3CO]. Anal. Calc. for C15H9O5N2Re: C, 37.19; H, 1.86. Found: C,
37.79; H, 1.97%.
d 40.7 (s, CH2); 83.7 (s, C5H4); 84.1 (s, C5H4); 106.2 (s, C5H4); 111.4
(s, C6H4); 126.4 (s, C6H4); 139.1 (s, C6H4); 152.2 (s, C6H4); 193.4 (s,
CO). Mass spectrum (based on 187Re) m/z: 486 [M+]; 458 [M+ÀCO];
430 [M+À2CO]; 402 [M+À3CO]; 349 [M+ÀNHC6H4-p-NO2]. Anal.
Calc. for C15H11O5N2Re: C, 37.04; H, 2.26. Found: C, 37.61; H, 2.37%.
4. Crystal structure determination
A summary of the fundamental crystal and refinement data for
1a and 1b are given in Table 1. Crystals of 1b and 2b were mounted
on a Brucker-Siemens Smart CCD diffractometer equipped with a
normal focus, 2.4 kW sealed tube X-ray source (Molybdenum radi-
ation, k = 0.71073 Å) operating at 50 kV and 20 mA. Data were col-
lected over a hemisphere of the reciprocal space by a combination
of three frame sets. The cell parameters were determined and re-
fined by least-squares fit of all reflection collected. Each frame
exposure time was of 20 s. covering 0.3° in x. The crystal to detec-
tor distance was 5.08 cm. The first 100 frames were recollected at
the end of the data collection to monitor crystal decay. Empirical
absorption corrections were made using SADABS program [16]. The
structure solution by direct methods, Fourier methods, and full
matrix least-square refinement was carried out using SHELXTL [17]
minimizing w(F2o À Fc2)2. Hydrogen atoms have been located y re-
fined isotropically except the hydrogen atoms of the methyl group
of the compound 1b. Weighted R factors (Rw) and all goodness of fitS
are based on F2, conventional R factors (R) are based on F.
3.4. (g5-C5H4CH2NHC6H5)Re(CO)3 (2a)
Complex 1a (50.0 mg, 0.114 mmol) was dissolved in anhydrous
methanol (10 ml) followed by addition an excess of solid NaBH4
(16.0 mg, 0.423 mmol). The mixture was stirred under nitrogen
atmosphere for 2 h. After this time, the IR spectrum showed the
complete disappearance of the imine complex 1a, and the presence
of two new absorption bands shifted to low energy (2020,
1924 cmÀ1). The white solid obtained after evaporation of metha-
nol was chromatographed on a silica gel column; elution with
CH2Cl2 moved the amine complex. The complex 2a was isolated
quantitatively as white solid, after crystallization from CH2Cl2/hex-
ane (1:5) at À18 °C. (Yield: 50.0 mg, 0.114, 100%). IR (CH2Cl2, mCO,
cmÀ1): 2024s, 1929s. 1H NMR (CDCl3) d: 4.14 (s, 2H, CH2); 5.28 (t,
J = 2.4 Hz, 2H, C5H4); 5.43 (t, J = 2.4 Hz, 2H, C5H4); 6.66 (d,
J = 7.8 Hz, 2H, C6H5); 6.78 (d, J = 7.3 Hz, 1H, C6H5); 7.22 (pseudo-
dt, 2H, C6H5). 1H NMR (C6D6) d: 3.19 (s, broad, 1H, NH); 3.48 (d,
J = 6.6 Hz, 2H, CH2); 4.38 (pseudo- t, 2H, C5H4); 4.58 (pseudo-t,
2H, C5H4); 6.37 (d, J = 7.7 Hz, 2H, C6H5); 6.79 (d, J = 7.3 Hz, 1H,
C6H5); 7.15 (t, J = 7.7 Hz, 2H, C6H5). 13C NMR (CDCl3) d: 41.4 (s,
CH2); 83.5 (s, C5H4); 83.7 (s, C5H4); 108.7 (s, C5H4); 113.1 (s,
C6H5); 118.5 (s, C6H5); 129.5 (s, C6H5); 147.3 (s, C6H5); 193.9
(CO). Mass spectrum (based on 187Re) m/z: 441 [M+]; 413
[M+ÀCO]; 385 [M+À2CO]; 357 [M+À3CO]; 349 [M+ÀNHC6H5]. Anal.
Calc. for C15H12O3NRe: C, 40.81; H, 2.72. Found: C, 40.94; H, 2.86%.
Acknowledgements
A.H.K. acknowledges FONDECYT (Project 1060487) and D.I. Pon-
tificia Universidad Catolica de Valparaiso. R.A. acknowledges
MECESUP and FONDECYT for a Doctoral scholarship. We also
appreciate the financial support of MECESUP (Project UCH 0116)
for a MS instrument. The loan of NH4ReO4 from MOLYMET – Chile
is also much appreciated.
Appendix A. Supplementary data
3.5. (g5-C5H4CH2NHC6H4OCH3-p)Re(CO)3 (2b)
CCDC 668276 and 668277 contain the supplementary crystallo-
graphic data for 1b and 2b. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: de-
posit@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2008.04.021.
Complex 2b was obtained following the same procedure de-
scribed for 2a. It was isolated as white crystals. (Yield: 50.0 mg,
0.106 mmol, 100%). IR (CH2Cl2, mCO, cmÀ1): 2022 s, 1926 s. 1H
NMR (CDCl3): d 3.76 (s, 3H, OCH3); 4.08 (s, 2H, CH2); 5.27 (t,
J = 2.4 Hz, 2H, C5H4); 5.41 (t, J = 2.4 Hz, 2H, C5H4); 6.63 (pseudo-
dt, 2H, C6H4); 6.80 (pseudo-dt, 2H, C6H4). 1H NMR (C6D6): d 2.98
(s, broad, 1H, NH); 3.44 (s, 3H, OCH3); 3.50 (d, J = 6.6 Hz, 2H,
CH2); 4.35 (t, J = 2.0 Hz, 2H, C5H4); 4.66 (t, J = 2.0 Hz, 2H, C5H4);
6.36 (pseudo-dt, 2H, C6H4); 6.81 (pseudo-dt, 2H, C6H4). 13C NMR
(CDCl3) d: 42.5(CH2); 55.6 (s, OCH3); 83.5 (s, C5H4); 83.6 (s,
C5H4); 108.8 (s, C5H4); 114.7 (s, C6H4); 115.5 (s, C6H4); 141.3 (s,
C6H4); 152.9 (s, C6H4); 193.94(CO). Mass spectrum (based on
187Re) m/z: 471 [M+]; 443 [M+ÀCO]; 415 [M+À2CO]; 387
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Complex 2b was obtained following the same procedure de-
scribed for 2a. It was isolated as white crystals. (Yield: 50.0 mg,
0.103 mmol, 100%). IR (CH2Cl2, mCO, cmÀ1): 2024 s, 1929 s. 1H
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