Complexes of the fac-{Re(CO)3}+ core with tridentate ligands derived from arylpiperazines

Article abstract of DOI:10.1016/j.ica.2003.11.027

Arylpiperazines, XC₆H₄N(CH₂CH ₂)₂NH, are readily alkylated to give the N-alkylpiperazines of the type XC₆H₄N(CH ₂CH₂)₂N(CH₂)_nNH ₂. The amine functions of these derivatives are in turn easily subjected to mono- or dialkylation to provide potentially tridentate ligands of the types XC₆H₄N(CH₂CH₂) ₂N(CH₂)_nN(H)(CH₂Y) and XC ₆H₄N(CH₂CH₂)₂N(CH ₂)_nN(CH₂Y)(CH₂Z), respectively. The latter class of dialkylated derivatives may be symmetrically (Y=Z) or unsymmetrically (Y≠Z) substituted. The donor groups Y and Z of this study include pyridine, imidazole, methyl-imidazole, thiazole, carboxylate and thiolate. The reactions of these ligands with [NEt₄] ₂[Re(CO)₃Br₃] yield complexes of the type [Re(CO)₃{(YCH₂)N(H)(CH₂)_n(H) _xN(CH₂CH₂)₂N(H)_yC ₆H₄X}]ⁿ and [Re(CO)₃{(ZCH ₂)(YCH₂)N(CH₂)_n(H) _xN(CH₂CH₂)₂N(H)_yC ₆H₄X}]ⁿ where the molecular charge n (0, +1, or +2) depends on the nature of the donor groups Y and Z (whether neutral or anionic or a combination of neutral and anionic) and on the degree of protonation of the piperazine unit (x=0 or 1; y=0 or 1). This variety of tridentate chelators provides complexes with fac-{Re(CO)₃N ₃}, {Re(CO)₃N₂O}, {Re(CO)₃NO ₂}, {Re(CO)₃N₂S} and {Re(CO)₃NS ₂} coordination geometries. The structures of the model compound [Re(CO)₃{(CH₃N₂C₃H ₂CH₂)N(H)CH₂CH₂-piperidine}] Br·H₂O, [Re(CO)₃{(CH₃N₂C ₃H₂CH₂)N(H)CH₂CH₂- Fphenpip}]Br, [Re(CO)₃{(NC₅H₄CH ₂)N(H)CH₂CH₂-Fphenpip}]Br, [Re(CO) ₃{(O₂CCH₂)₂NCH₂CH ₂CH₂-CH₃OphenpipH}]·xCH₃OH (x≈0.875), [Re(CO)₃{(NC₅H₄CH ₂)₂NCH₂CH₂CH₂-CH ₃OphenpipH}]Br₂·2CH₂Cl ₂·H₂O and [Re(CO)₃{(CH₃N ₂C₃H₂CH₂)(O₂CCH ₂)NCH₂CH₂CH₂-CH ₃OphenpipH₂}]BrCl·1.5CH₃OH·H ₂O are discussed (phenpip: phenylpiperazine, -C₆H ₄N(CH₂CH₂)₂N-).

Full text of DOI:10.1016/j.ica.2003.11.027

Inorganica Chimica Acta 357 (2004) 1499–1516
www.elsevier.com/locate/ica
Complexes of the fac-{Re(CO)3}þ core with tridentate ligands
derived from arylpiperazines
a
Lihui Wei , Sangeeta Ray Banerjee , Murali K. Levadala , John Babich ,
a
a
b
a,
*
Jon Zubieta
a
Department of Chemistry, Center for Science and Technology, Syracuse University, Syracuse, NY 13244, USA
b
Molecular Insight Pharmaceuticals Inc., 160 Second Street, Cambridge, MA 02142, USA
Received 7 November 2003; accepted 15 November 2003
Abstract
Arylpiperazines, XC6H4N(CH2CH2)2NH, are readily alkylated to give the N-alkylpiperazines of the type
XC6H4N(CH2CH2)2N(CH2)nNH2. The amine functions of these derivatives are in turn easily subjected to mono- or dialkylation to
provide potentially tridentate ligands of the types XC6H4N(CH2CH2)2N(CH2)nN(H)(CH2Y) and XC6H4N(CH2CH2)2N(CH2)n
N(CH2Y)(CH2Z), respectively. The latter class of dialkylated derivatives may be symmetrically (Y ¼ Z) or unsymmetrically (Y ¼ Z)
substituted. The donor groups Y and Z of this study include pyridine, imidazole, methyl-imidazole, thiazole, carboxylate and
thiolate.
The reactions of these ligands with [NEt4]2[Re(CO)3Br3] yield complexes of the type [Re(CO)3{(YCH2)N(H)(CH2)n(H)xN
(CH2CH2)2N(H)yC6H4X}]n and [Re(CO)3{(ZCH2)(YCH2)N(CH2)n(H)xN(CH2CH2)2N(H)yC6H4X}]n where the molecular charge
n (0, +1, or +2) depends on the nature of the donor groups Y and Z (whether neutral or anionic or a combination of neutral and
anionic) and on the degree of protonation of the piperazine unit (x ¼ 0 or 1; y ¼ 0 or 1). This variety of tridentate chelators provides
complexes with fac-{Re(CO)3N3}, {Re(CO)3N2O}, {Re(CO)3NO2}, {Re(CO)3N2S} and {Re(CO)3NS2} coordination geometries.
The structures of the model compound [Re(CO)3{(CH3N2C3H2CH2)N(H)CH2CH2-piperidine}]Br ꢀ H2O, [Re(CO)3{(CH3N2
C3H2CH2)N(H)CH2CH2-Fphenpip}]Br, [Re(CO)3{(NC5H4CH2)N(H)CH2CH2-Fphenpip}]Br, [Re(CO)3{(O2CCH2)2NCH2CH2
CH2-CH3OphenpipH}] ꢀ xCH3OH (x ꢁ 0:875), [Re(CO)3{(NC5H4CH2)2NCH2CH2CH2-CH3OphenpipH}]Br2 ꢀ 2CH2Cl2 ꢀ H2O and
[Re(CO)3{(CH3N2C3H2CH2)(O2CCH2)NCH2CH2CH2-CH3OphenpipH2}]BrCl ꢀ 1.5CH3OH ꢀ H2O are discussed (phenpip: phe-
nylpiperazine, –C6H4N(CH2CH2)2N–).
Ó 2003 Elsevier B.V. All rights reserved.
1. Introduction
ceutical reagents. In the case of technetium-based radi-
odiagnostics, the chemistry of the {TcO}3þ core has
dominated the literature [3]. More recently, the orga-
nometallic approach pioneered by Jaouen [4] has en-
couraged the development of the {Tc(CO)3}þ and
{Re(CO)3}þ cores as platforms for target-specific ra-
diopharmaceuticals [5–7]. Since the {M(CO)3}þ unit is
readily available as the air-stable fac-[M(CO)3(H2O)3]þ
species, a variety of monodentate, bidentate and tri-
dentate ligands will react with this reagent to displace
the substitutionally labile aqua ligands [8–10]. This
{M(CO)3}þ core is also attractive as a low spin d6 M(I)
center which is kinetically inert and possesses three fa-
cially disposed carbonyl donors which fix three coordi-
nation sites around the metal, leaving the three
The coordination chemistry of the Group VIIB
congeners technetium and rhenium has witnessed sig-
nificant activity, reflecting the importance of the radio-
isotopes 99mTc and 186;188Re in the development of
diagnostic and therapeutic radiopharmaceuticals, re-
spectively [1,2]. A noteworthy feature of the chemistry
of these elements is the accessibility of oxidation states
)I to +VII and the availability of robust core structures
suitable as platforms for development of radiopharma-
* Corresponding author. Tel.: +1-315-443-2547; fax: +1-315-443-
4070.
E-mail address: jazubiet@syr.edu (J. Zubieta).
0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2003.11.027

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L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
remaining facial positions available for substitution. The
small size of the core allows labeling of low molecular
weight biomolecules with high specific activities with
retention of biological activity and specificity.
thermodynamic stability. These tridentate chelating
systems have been incorporated into amino acid struc-
tures and the resulting single amino acid chelates have
been used to create large libraries of biologically active
peptides that can be readily radiolabeled with the ra-
dioisotopes of Tc and Re [27]. Combining the tridentate
chelating moiety which effectively binds the {M(CO)3}þ
core, with the rich phenylpiperazine pharmacophore
scaffold offers a new class of compounds that should be
explored for their biological activity and potential as
pharmacologically specific radiopharmaceuticals. The
tridentate chelating moiety can be designed to render the
overall metal ligand complex neutral which is key for
gaining access through the blood brain barrier. The
phenylpiperazine moiety offers rich opportunities for
modification. The overall molecular size of these com-
pounds, when complexed with Tc, appears to be below
the size limit imposed by the blood brain barrier. This
unique combination of characteristics suggests that
metal complexes of these novel phenylpiperazine chelate
derivatives should be explored for their utility for im-
aging biological systems especially in the central nervous
system.
Consequently, as part of our continuing investigations
of the {M(CO)3}þ core for radiopharmaceutical appli-
cations, we have designed a variety of derivatives of
arylpiperazine analogs which contain a chelating domain
structured to accommodate the {M(CO)3}þ core [28]. In
this work, we describe the syntheses and characterization
of thirteen arylpiperazine derived chelators and their
complexes with the {Re(CO)3}þ model core. The struc-
tures of [Re(CO)3{(CH3N2C3H2CH2)N(H)(CH2CH2)
(NC5H10)}]Br, [Re(CO)3 {(CH3N2C3H2CH2) N(H)CH2
CH2-Fphenpip}]Br, and [Re(CO)3{(O2CCH2)2NCH2
CH2CH2-CH3Ophenpip}] are presented, as well as the
full details for the structures of [Re(CO)3{(NC5H4CH2)
N(H)CH2CH2-Fphenpip}]Br, [Re(CO)3{(NC5H4CH2)2
NCH2CH2CH2-CH3OphenpipH}]Br2 and [Re(CO)3
{(CH3N2C3H2CH2)(O2CCH2)NCH2CH2CH2-CH3O
phenpipH2}]BrCl.
One class of biomolecules of particular interest for
derivatization with effective chelators for the
{Tc(CO)3}þ core are those which target neurotrans-
mitters, specifically the dopamine transporter sites
(DAT). Potential applications of a 99mTc-labeled ligand
for SPECT imaging of the DAT include diagnosis and
management of ParkinsonÕs disease [11], cocaine abuse
monitoring [12], and attention deficit hyperactivity dis-
order [13]. The majority of radiopharmaceuticals that
have been employed for the noninvasive measurement of
dopamine transporter sites are based on the structure of
the classical reuptake inhibitor cocaine [14], which has
itself been used as a PET ligand which concentrates in
the caudate-putamen where dopamine terminal density
is high [15]. Cocaine analogs with higher binding affinity
for dopamine transporter sites and more favorable
pharmacokinetic properties have been developed and
applied to imaging [16]. These include [11C] CFT (2b-
carbomethoxy-3b-(4-fluorophenyl)-tropane) [17] and
[11C] methylphenidate [18] for PET, and [123I] b-CIT
(2b-carbomethoxy-3b-(40-iodo-phenyl)tropane)
123I] IPT (N-(3-iodopropen-2-yl)-2b-carbomethoxy-3b-
[19],
[
(3,4-dichloro-phenyl)tropane) [20] and [99mTc] TRO-
DAT-1 [21] for SPECT imaging. Imaging agents based
on the cocaine antagonist piperidine derivatives have
also been developed [22–26]. The related arylpiperazine
(Scheme 1) derivatives of GBR 12935 have also been
shown to bind tightly to DAT and to inhibit dopamine
uptake at the DAT [23]. The phenylpiperazine phar-
macophore has also been derivatized in the development
of compounds with high affinities for several families of
receptor including the adrenergic, serotonergic and pu-
rinergic systems.
We have previously described a series of potentially
tridentate chelating systems that readily bind
{Tc(CO)3}þ and {Re(CO)3}þ with high kinetic and
2. Experimental
2.1. General methods
All reagents and organic solvents used in this study
are reagent grade and were used without further purifi-
cation. [NEt4]2[ReBr3(CO)3] [29] was prepared accord-
ing to the literature method. Acetonitrile used for
electrochemical experiments was dried by passing
through an alumina column just prior to the experi-
1
ments. H and 13C NMR spectra were recorded on a
Bruker DPX 300 spectrometer; all peak positions are
relative to TMS. IR spectra were recorded as KBr pellets
with a Perkin–Elmer Series 1600 FT-IR spectrometer in
Scheme 1.

L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
1501
the region of 400–4000 cmꢂ1 with polystyrene as refer-
ence. Electrospray mass spectrometry (ESMS) was per-
formed on a Hewlett Packard (Series 1100 MSD)
instrument with samples dissolved in methanol. Elec-
trochemical measurements were performed on a BAS
potentiostate (Model CV-27) equipped with data-col-
lecting and analyzing capabilities. Dry acetonitrile, de-
oxygenated under nitrogen atmosphere, was used as the
solvent with 0.1 M tetra-n-butylammonium hexaflu-
orophosphate, ([NBu4]PF6, TBAH) as supporting elec-
trolyte. A three-compartment glass cell, with a platinum
bead working electrode, a platinum wire counter elec-
trode, and a silver wire reference electrode, was used for
all experiments. Potential values were recorded without
junction correction. Ferrocene was used as an internal
standard. Under our experimental conditions, with a
scan rate of 50 mV/s, the ferrocenium/ferrocene couple
occured at E1=2 ¼ þ0:26 V. Carbon, hydrogen and ni-
trogen analyses were carried out by Oneida research
services, Whitesboro, NY.
to give 1. Yield: 3.324 g (0.0134 mol, 75%). 1H NMR (d
(ppm), CD3OD): 6.99–6.87 (m, 4H, Ph–OCH3), 3.78 (s,
3H, OCH3), 3.01 (m, 4H, ppz), 2.93 (t, 2H, CH2NH2),
2.59 (m, 4H, ppz), 2.48 (t, 2H, NCH2), 1.80 (m, 2H,
CH2). 13C NMR (d (ppm), CD3OD): 153.75 (C, Ph–
OCH3), 142.27 (C, Ph–OCH3), 124.47 (CH, Ph–OCH3),
122.22 (CH, Ph–OCH3), 119.38 (CH, Ph–OCH3), 112.92
(CH, Ph–OCH3), 57.21 (C, OCH3), 56.14 (2C, NCH2),
54.27 (2C, ppz), 51.61 (2C, ppz), 40.49 (C, CH2N), 26.55
(C, CH2).
1 (1.2 g, 0.0048 mol) and 2-chloromethylpyridine
hydrochloride (1.57 g, 0.0096 mol) were dissolved in
water (30 ml) and stirred at room temperature for two
days, with 5 M aqueous NaOH solution added to
maintain the pH at 8–10. The resulting dark red so-
lution was extracted with ethyl acetate and concen-
trated under vacuum. The residue was purified by
column chromatography using CH3OH/CH2Cl2 (5/95)
1
to give L1. Yield: 1.41 g (0.0026 mol, 55%). H NMR
(d (ppm), CDCl3): 8.47 (d, 2H, Py (pyridine)), 7.69 (t,
2H, Py), 7.53 (d, 2H, Py), 7.32 (t, 2H, Py), 6.95 (m, 4H,
Ph–OCH3), 3.85 (s, 4H, CH2Py), 3.83 (s, 3H, OCH3),
3.00 (m, 4H, ppz), 2.61 (m, 6H, ppz, NCH2Py), 2.41
(t, 2H, CH2N), 1.78 (m, 2H, CH2). 13C NMR (d
(ppm), CDCl3): 160.87 (2C, Py), 153.98 (C, Ph–OCH3),
149.54 (2CH, Py), 140.31 (C, Ph–OCH3), 138.79 (2CH,
Py), 125.02 (2CH, Py), 124.73 (2CH, Ph–OCH3),
123.91 (2CH, Py), 122.29 (CH, Ph–OCH3), 119.50
(CH, Ph–OCH3), 112.90 (CH, Ph–OCH3), 61.37 (2C,
CH2Py), 57.63 (C, OCH3), 56.05 (C, NCH2), 54.36
(2C, ppz), 53.81 (2C, CH2N), 51.64 (2C, ppz), 25.18
(C, CH2).
2.2. Ligand syntheses [Bis-(2-methylpyridyl)-{(4-(2-
methoxyphenyl)-1-piperazine-yl}-propyl-3-amine] (L1),
[4-(2-methoxyphenyl)-1-piperazine-yl-propyl-3-amine]
(1)
N-(3-bromopropyl)phthalimide (5.36 g, 0.02 mol) and
triethylamine (4.05 g, 0.04 mol) were added to a vigor-
ously stirred solution of 4-(2-methoxyphenyl)piperazine
(3.85 g, 0.02 mol) in toluene (100 ml). The reaction
mixture was refluxed under argon atmosphere overnight
and concentrated under reduced pressure. The residue
was purified by silica gel column chromatography using
dichloromethane to give 4-(-2-methoxyphenyl)-1-piper-
azine-yl-propyl-phthalimide as an oil product. Yield:
2.3. {3-[4-(2-Methoxy-phenyl)-piperazin-1-yl]-propyl}-
bis-(1-methyl-1H-imidazol-2-yl-methyl)-amine (L2)
1
6.75 g (0.0178 mol, 89%). H NMR (d (ppm), CDCl3):
7.85 (m, 2H, Ph (phthal)), 7.71 (m, 2H, Ph), 6.89 (m, 4H,
Ph–OCH3 (phenyl-OCH3)), 3.84 (s, 3H, OCH3), 3.81 (t,
2H, CH2N), 2.93 (m, 4H, ppz (piperazine)), 2.59 (m, 4H,
ppz), 2.50 (t, 2H, NCH2), 1.92 (m, 2H, CH2). 13C NMR
(d (ppm), CDCl3): 168.74 (2C, CO), 152.46 (C, Ph–
OCH3), 141.56 (C, Ph–OCH3), 134.03 (2CH, Ph),
132.59 (2C, Ph), 123.36 (2CH, Ph), 123.00 (CH, Ph–
OCH3), 121.11 (CH, Ph–OCH3), 118.30 (CH, Ph–
OCH3), 111.30 (CH, Ph–OCH3), 56.39 (C, OCH3),
55.52 (C, NCH2), 53.59 (2C, ppz), 50.74 (2C, ppz), 36.96
(C, CH2N), 25.46 (C, CH2). The product was dissolved
in 100 ml ethanol and hydrazine monohydrate (0.89 g,
0.0178 mol) was added. The reaction mixture was ref-
luxed under argon until a white gelatinous precipitate
formed. When precipitation was complete, concentrated
HCl was added. The phthalylhydrazide hydrochloride
precipitate was filtered, and the filtrate was concentrated
under vacuum. The residue was made basic with aque-
ous sodium bicarbonate and extracted with ethyl acetate
1 (0.406 g, 1.63 mmol) and 1-methyl-2-imidazolecar-
box-aldehyde (0.359 g, 3.26 mmol) were mixed in 1,2-
dichloroethane. Sodium triacetoxyborohydride (1.035 g,
4.89 mmol) was then added. The suspension was stirred
at ambient temperature under an argon atmosphere for
4 h. The reaction mixture was quenched by adding sat-
urated sodium bicarbonate solution and extracted with
dichloromethane. After concentrating the dichlorome-
thane layer under vacuum, the crude ligand was purified
by silica gel column chromatography using CH3OH/
CH2Cl2 (5/95) to give L2. Yield: 0.463 g (1.06 mmol,
1
Yield: 65%). H NMR (d (ppm), CDCl3): 6.93–6.75 (m,
8H, Ph–OCH3, Im (imidazole)), 3.79 (s, 3H, OCH3),
3.63 (s, 4H, CH2Im), 3.43 (s, 6H, NCH3), 3.02 (m, 4H,
ppz), 2.55 (m, 6H, ppz, NCH2), 2.27 (t, 2H, CH2N), 1.62
(m, 2H, CH2). 13C NMR (d (ppm), CDCl3): 152.18 (C,
Ph–OCH3), 145.21 (2C, Im), 141.06 (C, Ph–OCH3),
127.02 (2CH, Im), 123.00 (CH, Ph–OCH3), 121.43
(2CH, Im), 120.95 (CH, Ph–OCH3), 118.19 (CH, Ph–

1502
L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
OCH3), 111.14 (CH, Ph–OCH3), 56.22 (C, OCH3),
55.33 (C, NCH2), 53.23 (2C, ppz), 52.36 (C, CH2N),
50.23 (2C, ppz), 50.10 (2C, CH2Im), 32.48 (2C, NCH3),
23.69 (C, CH2).
was used instead of 1-methyl-2-imidazolecarboxalde-
1
hyde. Yield: 70%. H NMR (d (ppm), CDCl3): 6.92 (m,
4H, Ph–OCH3), 3.82 (s, 3H, OCH3), 3.35 (s, 4H,
CH2CO2), 3.19 (m, 4H, ppz), 3.03 (t, 2H, NCH2), 2.92
(m, 4H, ppz), 2.61 (t, 2H, CH2N), 1.92 (m, 2H, CH2).
13C NMR (d (ppm), CDCl3): 174.35 (2C, CO2H), 153.80
(C, Ph–OCH3), 141.98 (C, Ph–OCH3), 124.67 (CH, Ph–
OCH3), 122.24 (CH, Ph–OCH3), 119.67 (CH, Ph–
OCH3), 112.87 (CH, Ph–OCH3), 59.41 (C, OCH3),
57.80 (C, NCH2), 56.10 (2C, CH2CO2H), 54.19 (2C,
ppz), 50.58 (2C, ppz), 50.00 (C, CH2N), 21.82 (C, CH2).
2.4. {3-[4-(2-Methoxy-phenyl)-piperazin-1-yl]-propyl}-
bis-thiozol-2-ylmethyl-amine (L3)
The ligand was prepared by a similar procedure as
described in the case of L2, except that 2-thiazolecar-
boxaldehyde was used instead of 1-methyl-2-imidazole-
carbox-aldehyde. Starting from 1 (0.33 g, 1.325 mmol),
2-thiazolecarboxaldehyde (0.30 g, 2.65 mmol), and so-
dium tricarboxaldehyde (0.84 g, 3.98 mmol), ligand L3
was obtained in 82% yield. 1H NMR (d (ppm), CDCl3):
7.67 (d, 2H, Th (thiazole)), 7.26 (d, 2H, Th), 6.90 (m,
4H, Ph–OCH3), 4.04 (s, 4H, CH2Th), 3.81 (s, 3H,
OCH3), 3.03 (m, 4H, ppz), 2.68 (t, 2H, NCH2), 2.60 (m,
4H, ppz), 2.44 (t, 2H, CH2N), 1.78 (m, 2H, CH2). 13C
NMR (d (ppm), CDCl3): 170.79 (2C, Th), 152.22 (C,
Ph–OCH3), 142.40 (2CH, Th), 141.28 (C, Ph–OCH3),
122.88 (CH, Ph–OCH3), 120.97 (CH, Ph–OCH3), 119.55
(2CH, Th), 118.16 (CH, Ph–OCH3) 111.14 (CH, Ph–
OCH3), 56.10 (C, OCH3), 55.85 (2C, ppz), 55.33 (C,
NCH2), 53.37 (2C, ppz), 52.21 (C, CH2N), 50.54 (2C,
CH2Th), 24.63 (C, CH2).
2.7. {3-[4-(2-Methoxyphenyl)-piperazin-1-yl]-propyl}-
(1-methyl-1H-imidazol-2-ylmethyl)-amine (2)
1 (6.32 g, 0.0254 mol) and 1-methyl-2-imidazolecar-
boxaldehyde (2.795 g, 0.0254 mol) were dissolved in
methanol (100 ml) and refluxed under an argon atmo-
sphere for 2 h. Sodium borohydride (0.945 g, 0.0254
mol) was added to the reaction mixture which was then
stirred for another 3 h and concentrated. The residue
was extracted with chloroform, dried over sodium sul-
fate and concentrated. The crude product thus obtained
was purified by silica gel column chromatography using
CH3OH/CHCl3 (8/92) to give 2 as a brown oil. Yield:
1
6.97 g (0.0203 mol, 80%). H NMR (d (ppm), CDCl3):
6.97–6.77 (m, 6H, Ph–OCH3, Im), 3.81 (bs, 5H, OCH3,
CH2Im), 3.62 (s, 3H, NCH3), 3.05 (m, 4H, ppz), 2.70 (t,
2H, CH2N), 2.61 (m, 4H, ppz), 2.45 (t, 2H, NCH2), 1.71
(m, 2H, CH2). 13C NMR (d (ppm), CDCl3): 151.84 (C,
Im), 146.25 (C, Ph–OCH3), 140.97 (C, Ph–OCH3),
126.63 (CH, Im), 122.44 (CH, Ph–OCH3), 120.75 (CH,
Im), 120.58 (CH, Ph–OCH3), 117.74 (CH, Ph–OCH3),
110.81 (CH, Ph–OCH3), 56.43 (C, OCH3), 54.96 (C,
NCH2), 53.12 (2C, ppz), 50.25 (2C, ppz), 47.78
(C, CH2N), 45.49 (C, CH2Im), 32.29 (C, CH2), 26.67 (C,
NCH3).
2.5. {3-[4-(2-Methoxy-phenyl)-piperazin-1-yl]-propyl}-
bis-quinolin-2-ylmethyl-amine (L4)
The ligand was prepared by a similar procedure as
described in the case of L2, except that 2-quinolinecar-
boxaldehyde was used instead of 1-methyl-2-imidazole-
carbox-aldehyde. Yield: 80%. 1H NMR (d (ppm),
CDCl3): 8.08 (m, 4H, Qu (quinoline)), 7.68 (m, 6H, Qu),
7.48 (t, 2H, Qu), 6.99–6.81 (m, 4H, Ph–OCH3), 4.03 (s,
4H, CH2Qu), 3.82 (s, 3H, OCH3), 3.04 (m, 4H, ppz),
2.69 (m, 6H, ppz, NCH2), 2.50 (t, 2H, CH2N), 1.88 (m,
2H, CH2). 13C NMR (d (ppm), CDCl3): 160.48 (2C,
Qu), 152.21 (C, Ph–OCH3), 147.54 (2C, Qu), 140.89 (C,
Ph–OCH3), 136.50 (2CH, Qu), 129.52 (2CH, Qu),
129.00 (2CH, Qu), 127.60 (2CH, Qu) 127.42 (2C, Qu),
126.27 (2CH, Qu), 123.21 (CH, Ph–OCH3), 121.23
(2CH, Qu), 121.05 (CH, Ph–OCH3), 118.36 (CH, Ph–
OCH3), 111.20 (CH, Ph–OCH3), 61.42 (2C, ppz), 56.15
(C, NCH2), 55.40 (C, OCH3), 52.96 (2C, ppz), 52.52 (C,
CH2N), 49.87 (2C, CH2Qu), 23.62 (C, CH2).
2.8. {3-[4-(2-Methoxy-phenyl)-piperazin-1-yl]-propyl}-
pyridin-2-ylmethyl-amine (3)
The compound was prepared by a similar procedure
as described in the case of 2, except that 2-pyridinecar-
boxaldehyde was used instead of 1-methyl-2-imidazole-
carboxaldehyde. Yield: 82%. 1H NMR (d (ppm),
CDCl3): 8.28 (d, 1H, Py), 7.40 (t, 1H, Py), 7.09 (d, 1H,
Py), 6.92 (t, 1H, Py), 6.67 (m, 4H, Ph–OCH3), 3.81 (s,
2H, CH2Py), 3.58 (s, 3H, OCH3), 2.88 (m, 4H, ppz), 2.69
(t, 2H, CH2N), 2.50 (m, 4H, ppz), 2.34 (t, 2H, NCH2),
1.66 (m, 2H, CH2). 13C NMR (d (ppm), CDCl3): 155.90
(C, Py), 151.34 (CH, Py), 148.35 (C, Ph–OCH3), 140.36
(CH, Py), 135.95 (C, Ph–OCH3), 122.36 (CH, Py),
122.05 (2CH, Ph–OCH3), 120.13 (CH, Py), 117.23 (CH,
Ph–OCH3), 110.41 (CH, Ph–OCH3), 56.50 (C, CH2Py),
2.6. (Carboxymethyl-{3-[4-(2-methoxy-phenyl)-pipera-
zin-1-yl]-propyl}-amino)-acetic acid (L5)
The ligand was prepared by a similar procedure as
described in the case of L2, except that glyoxylic acid

L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
1503
54.53 (C, OCH3), 52.90 (C, NCH2), 52.58 (2C, ppz),
49.56 (2C, ppz), 44.61 (C, CH2N), 24.22 (C, CH2).
2.11. {3-[4-(2-Methoxy-phenyl)-piperazin-1-yl]-propyl}-
pyridin-2-ylmethyl-thiazol-2-ylmethyl-amine (L8)
The ligand was prepared by a similar procedure as
described in the case of L6, except that 3 and 2-thia-
zolecarboxaldehyde were used instead of 2 and 2-pyri-
dinecarboxaldehyde. Yield: 77%. 1H NMR (d (ppm),
CDCl3): 8.49 (d, 1H, Py), 7.63 (d, 1H, Th), 7.61 (d, 1H,
Py), 7.59 (t, 1H, Py), 7.25 (t, 1H, Py), 6.91 (m, 4H, Ph–
OCH3), 4.00 (s, 2H, CH2Py), 3.86 (s, 2H, CH2Th), 3.82
(s, 3H, OCH3), 3.03 (m, 4H, ppz), 2.64 (t, 2H, CH2N),
2.60 (m, 4H, ppz), 2.41 (t, 2H, NCH2), 1.78 (m, 2H,
CH2). 13C NMR (d (ppm), CDCl3): 171.79 (C, Th),
159.37 (C, Py), 152.27 (C, Ph–OCH3), 149.02 (C, Py),
142.41 (CH, Th), 141.34 (C, Ph–OCH3), 136.58 (CH,
Py), 122.94 (CH, Ph–OCH3), 122.83 (CH, Py), 122.18
(CH, Py), 121.02 (CH, Ph–OCH3), 119.32 (CH, Th),
118.21 (CH, Ph–OCH3), 111.18 (CH, Ph–OCH3), 60.52
(C, CH2Th), 56.34 (C, NCH2), 55.85 (C, CH2Py), 55.38
(C, OCH3), 53.45 (2C, ppz), 52.40 (C, CH2N), 50.62
(2C, ppz), 24.62 (C, CH2).
2.9. {3-[4-(2-Methoxy-phenyl)-piperazin-1-yl]-propyl}-
(1-methyl-1H-imidazol-2-ylmethyl)-pyridin-2-ylmethyl-
amine (L6)
2 (0.112 g, 0.327 mmol) and 2-pyridine-carboxalde-
hyde (0.035 g, 0.327 mmol) were mixed in 1,2-dichlo-
roethane. Sodium triacetoxyborohydride (0.097 g, 0.457
mmol) was then added. The suspension was stirred at
room temperature for 4 h. The reaction mixture was
quenched with saturated sodium bicarbonate solution
and extracted with chloroform whereupon the organic
layer was concentrated under vacuum. The crude
product was purified by silica gel column chromatog-
raphy using CH3OH/CHCl3 (6/94) to give L6. Yield:
0.121 g (0.279 mmol, 85%). 1H NMR (d (ppm), CDCl3):
8.52 (d, 1H, Py), 7.63 (t, 1H, Py), 7.35 (d, 1H, Py), 7.14
(t, 1H, Py), 7.00–6.83 (m, 4H, Ph–OCH3), 6.89 (d, 1H,
Im), 6.78 (d, 1H, Im), 3.84 (s, 3H, OCH3), 3.74 (s, 2H,
CH2Py), 3.73 (s, 2H, CH2Im), 3.60 (s, 3H, NCH3), 3.05
(m, 4H, ppz), 2.57 (m, 6H, ppz, NCH2), 2.33 (t, 2H,
CH2N), 1.73 (m, 2H, CH2). 13C NMR (d (ppm),
CDCl3): 159.48 (C, Py), 152.39 (C, Im), 149.18 (CH,
Py), 145.53 (C, Ph–OCH3), 141.46 (C, Ph–OCH3),
136.39 (CH, Py), 127.25 (CH, Im), 123.52 (CH, Py),
123.04 (CH, Im), 122.14 (CH, Ph–OCH3), 121.66 (CH,
Py), 121.12 (CH, Ph–OCH3), 118.32 (CH, Ph–OCH3),
111.28 (CH, Ph–OCH3), 60.47 (C, CH2Py), 56.62 (C,
OCH3), 55.48 (C, NCH2), 53.55 (2C, ppz), 52.60 (C,
CH2N), 51.34 (C, CH2Im), 50.72 (2C, ppz), 33.01 (C,
NCH3), 24.30 (C, CH2).
2.12. {3-[4-(2-Methoxyphenyl)-piperazine-1-yl)-propyl}-
acid
(1-methyl-1H-imidazol-2-ylmethyl)-amino]-acetic
benzyl ester (4)
To a solution of 2 (1.234 g, 0.0036 mol) in toluene
was added benzyl-2-bromoacetate (0.907 g, 0.004 mol),
triethylamine (1.001 g, 0.01 mol) and potassium iodide
(0.896 g, 0.0054 mol). The reaction mixture was refluxed
under argon atmosphere for 3 h and concentrated. After
extracting the residue with chloroform, the organic layer
was concentrated and purified by silica gel column
chromatography using CH3OH/CHCl3 (3/97) to give 4.
Yield: 1.06 g (60%). 1H NMR (d (ppm), CDCl3): 7.35 (s,
5H, Ph), 7.03–6.79 (m, 6H, Ph–OCH3, Im), 5.12 (s, 2H,
OCH2), 3.86 (s, 3H, OCH3), 3.84 (s, 2H, CH2Im), 3.73
(s, 3H, NCH3), 3.38 (s, 2H, CH2CO2), 3.07 (m, 4H,
ppz), 2.66–2.52 (m, 6H, NCH2, ppz), 2.35 (t, 2H,
CH2N), 1.66 (m, 2H, CH2). 13C NMR (d (ppm),
CDCl3): 170.87 (C, CO2), 152.15 (C, Im), 144.89 (C, Ph–
OCH3), 141.25 (C, Ph), 135.62 (C, Ph–OCH3), 128.48
(2CH, Ph), 128.23 (3CH, Ph), 126.99 (CH, Im), 122.77
(CH, Im), 121.67 (CH, Ph–OCH3), 120.89 (CH, Ph–
OCH3), 118.06 (CH, Ph–OCH3), 111.08 (CH, Ph–
OCH3), 66.12 (C, CH2Ph), 56.13 (C, CH2CO2), 55.24
(C, OCH3), 54.73 (C, NCH2), 53.34 (2C, ppz), 52.22 (C,
CH2N), 51.39 (C, CH2Im), 50.53 (2C, ppz), 32.78 (C,
CH2), 24.53 (C, NCH3).
2.10. {3-[4-(2-Methoxy-phenyl)-piperazin-1-yl]-propyl}-
(1-methyl-1H-imidazol-2-ylmethyl)-thiazol-2-ylmethyl-
amine (L7)
The ligand was prepared by a similar procedure as
described in the case of L6, except that 2-thiazolecar-
boxaldehyde was used instead of 2-pyridinecarboxalde-
1
hyde. Yield: 62%. H NMR (d (ppm), CDCl3): 7.64 (d,
1H, Th), 7.22 (d, 1H, Th), 6.98–6.82 (m, 4H, Ph–OCH3),
6.88 (d, 1H, Im), 6.80 (d, 1H, Im), 4.04 (s, 2H, CH2Th),
3.80 (s, 3H, OCH3), 3.78 (s, 2H, CH2Im), 3.68 (s, 3H,
NCH3), 3.04 (m, 4H, ppz), 2.59 (m, 6H, ppz, NCH2),
2.37 (t, 2H, CH2N), 1.73 (m, 2H, CH2). 13C NMR (d
(ppm), CDCl3): 170.56 (C, Th), 152.21 (C, Im), 144.75
(C, Ph–OCH3), 142.36 (CH, Th), 141.11 (C, Ph–OCH3),
127.11 (CH, Im), 123.02 (CH, Ph–OCH3), 121.84 (CH,
Im), 120.99 (CH, Ph–OCH3), 119.37 (CH, Th), 118.21
(CH, Ph–OCH3), 111.17 (CH, Ph–OCH3), 56.21 (C,
OCH3), 55.35 (2C, CH2Im, CH2Th), 53.27 (2C, ppz),
52.52 (C, NCH2), 51.15 (C, CH2N), 50.31 (2C, ppz),
33.10 (C, NCH3), 23.96 (C, CH2).
2.13. {3-[4-(2-Methoxy-phenyl-piperazin-1-yl]-propyl}-
(1-methyl-1H-imidazol-2-ylmethyl)-amino]-acetic acid
(L9)
A solution of 4 (1.06 g, 0.002 mol) in methanol (20
ml) was hydrogenated at atmospheric pressure and

1504
L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
room temperature with 10% palladium charcoal for 12
h. The catalyst was filtered through celite, and the fil-
trate was evaporated to give L9. Yield: 0.68 g (0.0012
ppz). 13C NMR (d (ppm), CDCl3): 168.45 (2C, CO),
154.15 (C, Ph–F), 140.32 (C, Ph–F), 133.97 (2CH, Ph)
132.31 (2C, Ph), 124.50 (CH, Ph–F), 123.30 (2CH, Ph),
122.42 (CH, Ph–F), 118.99 (CH, Ph–F), 116.29 (CH,
Ph–F), 55.84 (C, NCH2), 53.23 (2C, ppz), 50.63 (2C,
ppz), 35.35 (C, NCH2Ph). The product was dissolved in
a mixture of ethanol–dichloromethane (100 ml, 3:2), and
hydrazine monohydrate (0.72 g, 0.014 mol) was added.
The reaction mixture was refluxed under argon until a
white gelatinous precipitate formed. When the precipi-
tation was complete, concentrated HCl was added. The
phthalylhydrazide hydrochloride precipitate was fil-
tered, and the filtrate was concentrated under vacuum.
The residue was made basic with aqueous sodium bi-
carbonate and extracted with ethyl acetate to give 5.
Yield: 1.2 g (0.0056 mol, 40%). 1H NMR (d (ppm),
CDCl3): 6.91 (m, 4H, Ph–F), 3.77 (bs, 2H, NH2), 2.99
(m, 4H, ppz), 2.56 (m, 2H, CH2NH2), 2.51 (m, 4H, ppz),
2.39 (t, 2H, NCH2). 13C NMR (d (ppm), CDCl3): 153.82
(C, Ph–F), 139.94 (C, Ph–F), 124.26 (CH, Ph–F), 122.23
(CH, Ph–F), 118.70 (CH, Ph–F), 115.71 (CH, Ph–F),
60.02 (C, NCH2), 56.50 (2C, ppz), 53.00 (2C, ppz), 38.11
(C, CH2NH2).
1
mol, 60%). H NMR (d (ppm), CDCl3): 10.6 (bs, 1H,
CO2H), 6.92–6.72 (m, 6H, Im, Ph–OCH3), 3.72 (s, 3H,
OCH3), 3.70 (s, 2H, CH2Im), 3.65 (s, 3H, NCH3), 3.27
(s, 2H, CH2CO2), 3.13 (m, 4H, ppz), 3.07 (m, 4H, ppz),
2.78 (t, 2H, CH2N), 2.62 (t, H, NCH2), 1.75 (m, 2H,
CH2). 13C NMR (d (ppm), CDCl3): 175.28 (C, CO2H),
151.86 (C, Im), 144.85 (C, Ph–OCH3), 139.69 (C, Ph–
OCH3), 126.40 (CH, Im), 123.47 (CH, Im), 121.41 (CH,
Ph–OCH3), 120.83 (CH, Ph–OCH3), 118.26 (CH, Ph–
OCH3), 111.05 (CH, Ph–OCH3), 57.92 (C, CH2CO2H),
57.31 (C, OCH3), 56.56 (C, NCH2), 55.22 (C, CH2N),
52.47 (2C, ppz), 49.65 (2C, ppz), 48.17 (C, CH2Im),
32.97 (C, CH2), 21.77 (C, NCH3).
2.14. {3-[4-(2-Methoxy-phenyl)-piperazin-1-yl]-propyl)}-
pyridin-2-ylmethyl-amino)-acetic acid (L10)
3 (0.308 g, 0.904 mmol) and glyoxylic acid (0.109 g,
0.995 mmol) were mixed in dichloroethane, and sodium
triacetoxyborohydride (0.288 g, 1.357 mmol) was then
added. The suspension was stirred at room temperature
under argon for 3 h. The mixture was quenched with
saturated sodium bicarbonate solution and extracted
with dichloromethane. The dichloromethane layer was
concentrated under vacuum. The crude product was
purified by silica gel column chromatography using
CH3OH/CHCl3 (16/84) to give L10. Yield: 0.284 g
(0.714 mmol, 79%). 1H NMR (d (ppm), CDCl3): 8.45 (d,
1H, Py), 7.58 (t, 1H, Py), 7.22 (d, 1H, Py), 7.12 (t, 1H,
Py), 6.95 (m, 4H, Ph–OCH3), 3.81 (s, 3H, OCH3), 3.66
(s, 2H, CH2Py), 3.24 (m, 8H, ppz), 3.13 (s, 2H,
CH2CO2H), 2.99 (t, 2H, NCH2), 2.73 (t, 2H, CH2N),
1.89 (m, 2H, CH2). 13C NMR (d (ppm), CDCl3): 175.71
(C, CO2H), 157.67 (C, Py), 152.03 (CH, Py), 149.41 (C,
Ph–OCH3), 139.79 (CH, Py), 136.59 (C, Ph–OCH3),
124.01 (CH, Py), 123.75 (CH, Ph–OCH3), 122.48 (CH,
Py), 121.12 (CH, Ph–OCH3), 118.65 (CH, Ph–OCH3),
111.20 (CH, Ph–OCH3), 60.23 (C, CH2Py), 58.47 (C,
CH2CO2H), 57.67 (C, NCH2), 55.45 (C, OCH3), 53.65
(C, CH2N), 52.83 (2C, ppz), 48.10 (2C, ppz), 21.70 (C,
CH2).
2.16. [(2-Methylpyridyl)-{(4-(2-fluorophenyl)(1-ethyl-
piperazine-yl)}-amine] (L11)
5 (1.2 g, 0.005 mol) and pyridine-2-carboxaldehyde
(0.57 g, 0.005 mol) were dissolved in methanol (25 ml)
and refluxed under argon atmosphere for 2 h. Sodium
borohydride (0.2 g, 0.005 mol) was added to the reaction
mixture which was then stirred for another 3 h and
concentrated. The residue was extracted with dichlo-
romethane, dried over sodium sulfate and concentrated.
The crude product thus obtained was purified by silica
gel column chromatography using CH3OH/CHCl3 (4/
1
96) to give L11. Yield: 1.23 g (0.00375 mol, 75%). H
NMR (d (ppm), CDCl3): 8.53 (d, 1H, Py), 7.60 (t, 1H,
Py), 7.31 (d, 1H, Py), 7.14 (t, 1H, Py), 7.01–6.80 (m, 4H,
Ph–F), 3.97 (s, 2H, CH2Py), 3.44 (bs, 1H, NH), 3.09 (m,
4H, ppz), 2.80 (t, 2H, NCH2) 2.61 (m, 6H, CH2N, ppz).
13C NMR (d (ppm), CDCl3): 158.99 (C, Py), 154.22 (C,
Ph–F), 149.42 (CH, Py), 140.30 (C, Ph–F). 136.75 (CH,
Py), 124.56 (CH, Py), 123.53 (2CH, Ph–F), 119.04 (CH,
Py), 116.07 (2CH, Ph–F), 56.98 (C, NCH2), 54.22 (C,
CH2Py), 53.50 (2C, ppz), 50.44 (2C, ppz), 45.49 (C,
CH2N).
2.15. [4-(2-Fluorophenyl)-1-piperazine-yl-ethyl-2-amine]
(5)
The compound was prepared by a similar method as
described in the case of 1, starting with N-(2-bromo-
ethyl)phthalimide (7.05 g, 0.027 mol) and 1-(2-fluor-
ophenyl)piperazine (5 g, 0.027 mol) to give [4-(2-
fluorophenyl)-1-piperazine-yl-ethyl-phthalimide. Yield:
5.1 g (0.0014 mol, 52%). H NMR (d (ppm), CDCl3):
7.83 (m, 2H, Ph), 7.69 (m, 2H, Ph), 6.99 (m, 4H, Ph–F),
3.84 (t, 2H, CH2Ph), 3.04 (m, 4H, ppz), 2.70 (m, 6H,
2.17. {2-[4-(2-Fluoro-phenyl)-piperazin-1-yl]-ethyl}-(1-
methyl-1H-imidazol-2-ylmethyl)-amine (L12)
The compound was prepared by a similar procedure
as described in the case of L11, except that 1-methyl-2-
imidazolecarboxaldehyde was used instead of pyridine-
2-carboxaldehyde. Yield: 70%. 1H NMR (d (ppm),
CDCl3): 6.99–6.81 (m, Im, Ph–F), 3.89 (s, 2H, CH2Im),
1

L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
1505
3.05 (m, 4H, ppz), 2.76 (t, 2H, CH2N), 2.57 (m, 4H,
ppz), 2.48 (t, 2H, NCH2). 13C NMR (d (ppm), CDCl3):
157.21 (C, Im), 154.34 (C, Ph–F), 148.33 (C, Ph–F),
139.99 (CH, Im), 125.57 (CH, Ph–F), 122.32 (CH, Ph–
F), 121.78 (CH, Im), 119.56 (CH, Ph–F), 116.82 (CH,
Ph–F), 58.71 (C, NCH2), 53.64 (2C, ppz), 50.11 (2C,
ppz), 47.55 (C, CH2Im), 45.97 (C, CH2N).
Br2 ꢀ 2CH2Cl2 ꢀ H2O (7Br2 ꢀ 2CH2Cl2 ꢀ H2O) is presented
in detail.
2.20.1. [Re(CO)3(L1)]Br2 ꢀ 2CH2Cl2 ꢀ H2O (7Br2 ꢀ
2CH2Cl2 ꢀ H2O)
To a stirred solution of [NEt4]2[Re(CO)3Br3] (0.078 g,
0.102 mmol) in 20 ml methanol was added L1 (0.044 g,
0.102 mmol) in 2 ml methanol. The solution was ref-
luxed for 3 h. After cooling to room temperature, the
reaction mixture was evaporated to dryness. The residue
was dissolved in dichloromethane and carefully layered
with hexane. Colorless crystals suitable for X-ray crys-
tallography were obtained. Yield: 80%. Anal. Calc. for
C29H34Br2N5O4Re: C, 40.38; H, 3.97; N, 8.12. Found:
C, 40.16; H, 4.05; N, 8.23%. 1H NMR (d (ppm),
CD3OD): 8.92 (d, 2H, Py), 8.02 (t, 2H, Py), 7.69 (d, 2H,
Py), 7.44 (t, 2H, Py), 7.11–6.94 (m, 4H, Ph–OCH3), 5.13
(d, 2H, CH2Py), 4.95 (d, 2H, CH2Py) 3.96 (m, 2H,
NCH2), 3.93 (s, 3H, OCH3), 3.23 (m, 4H, ppz), 3.12 (m,
4H, ppz), 2.82 (t, 2H, CH2N), 2.35 (m, 2H, CH2). 13C
NMR (d (ppm), CD3OD): 197.37, 196.05 (fac-Re(CO)3),
162.19 (2C, Py), 153.97 (C, Ph–OCH3), 153.19 (2CH,
Py), 142.02 (C, Ph–OCH3), 141.72 (2CH, Py), 127.03
(2CH, Py), 124.90 (3CH, Py, Ph–OCH3), 122.32 (CH,
Ph–OCH3), 119.61 (CH, Ph–OCH3), 113.01 (CH, Ph–
OCH3), 69.72 (C, NCH2), 68.85 (2C, CH2Py), 56.15 (C,
OCH3), 56.08 (C, CH2N), 53.41 (2C, ppz), 51.24 (2C,
ppz), 23.11 (C, CH2). IR (KBr, m/cmꢂ1): 2029, 1913
(m(fac-Re(CO)3)). Mass spectrum (ESIMS): m=z ¼ [Re
(CO)3(L1)]þ ¼ 702.2. Cyclic voltammetry (Epa(II/I)):
1.02 V.
2.18. 2-({2-[4-(2-Fluoro-phenyl)piperazine-1yl]-3hyl}-
pyridin-2-ylmethyl-amino)-ethanthiol (L13)
To a solution of L11 (0.5 g, 1.5 mmol) in toluene was
added ethylene sulfide (0.19 g, 3.2 mmol), whereupon
the solution refluxed for 2 d under argon atmosphere.
The solution was filtered and the filtrate was concen-
trated under argon atmosphere to give L13. Yield: 0.23 g
1
(0.6 mmol, 40%). H NMR (d (ppm), CDCl3): 8.45 (d,
1H, Py), 7.58 (t, 1H, Py), 7.46 (d, 1H, Py), 7.2–6.82 (m,
5H, Py, Ph–F), 3.86 (s, 2H, CH2Py), 3.05 (m, 4H, ppz),
2.82–2.50 (m, 12H, NCH2CH2S, CH2N, ppz). 13C
NMR (d (ppm), CDCl3): 159.46 (C, Py), 157.15 (C, Ph–
F), 148.83 (CH, Py), 139.69 (C, Ph–F), 136.35 (CH, Py),
124.38 (CH, Py), 123.00 (CH, Py), 122.37 (CH, Ph–F),
121.97 (CH, Ph–F), 118.07 (CH, Ph–F), 116.00 (CH,
Ph–F), 60.47 (C, Py), 57.39 (C, CH2N), 56.09 (C,
NCH2), 53.41 (2C, ppz), 50.93 (C, CH2N), 49.99 (2C,
ppz), 22.72 (C, CH2SH).
2.19. (1-Methyl-1H-imidazol-2-ylmethyl)-(2-piperidin-1-
yl-ethyl)-amine (L14)
1-Methyl-2-imidazolecarboxaldehyde (2 g, 0.0182
mol) and 1-(2-aminoethyl)-piperidine (2.33 g, 0.0182
mol) were dissolved in 15 ml methanol and stirred at
room temperature for 2 h. Sodium borohydride (0.69 g,
0.0182 mol) was added to the solution, and the reaction
mixture was stirred for another 3 h. After concentration
under vacuum, the residue was dissolved in minimum
amount of dichloromethane, washed with water, dried
over sodium sulfate, and concentrated. The crude ligand
was purified by silica gel column chromatography using
CH3OH/CH2Cl2 (7/93) to give L14. Yield: 3.47 g (0.0157
2.20.2. [Re(CO)3(L14)]Br ꢀ H2O (6Br ꢀ H2O)
Yield: 79%. Anal. Calc. for C15H22BrN4O3Re: C,
31.47; H, 3.87; N, 9.79. Found: C, 31.58; H, 4.01; N,
1
9.65%. H NMR (d (ppm), CD3OD): 7.37 (d, 1H, Im),
7.22 (d, 1H, Im), 4.64 (d, 1H, CH2Im), 4.51 (d, 1H,
CH2Im), 3.86 (s, 3H, NCH3), 3.63–3.48 (m, 1H, CH2N),
3.31–3.24 (m, 1H, CH2N), 3.06 (m, 1H, NCH2), 2.86 (m,
1H, NCH2), 2.39 (m, 4H, ppd), 2.01–1.59 (m, 6H, ppd).
13C NMR (d (ppm), CD3OD): 197.81, 197.50, 193.61
(fac-Re(CO)3), 154.86 (C, Im), 129.08 (CH, Im), 126.18
(CH, Im), 64.83 (C, NCH2), 60.53 (2C, ppd), 54.27 (C,
CH2N), 51.97 (C, CH2Im), 35.54 (C, NCH2), 24.91 (C,
ppd), 24.71 (C, ppd), 23.99 (C, ppd). IR (KBr, m/cmꢂ1):
2015, 1903 (m(fac-Re(CO)3)).
1
mol, 86%). H NMR (d (ppm), CD3OD): 6.99 (d, 1H,
Im), 6.84 (d, 1H, Im), 3.82 (s, 2H, CH2Im), 3.69 (s, 3H,
NCH3), 2.70 (t, 2H, CH2N), 2.42 (t, 2H, NCH2), 2.37
(m, 4H, ppd (piperidine)), 1.55 (m, 4H, ppd), 1.43 (m,
2H, ppd). 13C NMR (d (ppm), CD3OD): 147.67 (C, Im),
127.24 (CH, Im), 123.09 (CH, Im), 59.31 (C, NCH2),
55.82 (2C, ppd), 46.62 (C, CH2N), 45.40 (C, CH2Im),
33.29 (C, NCH3), 26.81 (2C, ppd), 25.39 (C, ppd).
2.20.3. [Re(CO)3(L2)]Br2 (8Br2)
Yield: 78%. Anal. Calc. for C27H36Br2N7O4Re: C,
37.33; H, 4.18; N, 11.29. Found: C, 37.54; H, 4.10; N,
1
11.33%. H NMR (d (ppm), CDCl3): 6.96 (d, 2H, Im),
2.20. Syntheses of rhenium complexes of the ligands L1–
L14
6.95 (m, 4H, Ph–OCH3), 6.79 (d, 2H, Im), 4.58 (d,
2H,CH2Im), 4.23 (d, 2H, CH2Im) 3.87 (s, 3H, OCH3),
3.84 (s, 6H, NCH3), 3.78 (m, 2H, CH2N), 3.16 (m, 4H,
ppz), 2.79 (m, 4H, ppz), 2.57 (t, 2H, CH2N), 2.28 (m, 2H,
CH2). 13C NMR (d (ppm), CDCl3): 196.38, 194.71 (fac-
The complexes were prepared by similar procedures.
A representative synthesis for complex [Re(CO)3(L1)]

1506
L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
Re(CO)3), 152.43 (C, Ph–OCH3), 150.22 (2C, Im),
141.33 (C, Ph–OCH3), 128.16 (2CH, Im), 123.68 (2CH,
Im), 123.17 (CH, Ph–OCH3), 121.16 (CH, Ph–OCH3),
118.46 (CH, Ph–OCH3), 111.38 (CH, Ph–OCH3), 59.07
(C, OCH3), 55.59 (2C, CH2Im), 55.43 (C, NCH2), 53.91
(2C, ppz), 53.64 (C, CH2N), 50.65 (2C, ppz), 35.84 (2C,
NCH3), 23.11 (C, CH2). IR (KBr, m/cmꢂ1): 2025, 1888
(m(fac-Re(CO)3)). Mass spectrum (ESIMS): m=z ¼ [Re
(CO)3(L2)]þ ¼ 708.2. Cyclic voltammetry (Epa(II/I)):
0.97 V.
3.79 (s, 3H, OCH3), 3.56 (d, 2H, CH2CO2), 3.43 (d, 2H,
CH2CO2), 3.34 (m, 4H, ppz), 3.26 (t, 2H, NCH2), 3.16
(m, 4H, ppz), 2.91 (m, 2H, CH2N), 2.02 (m, 2H, CH2).
13C NMR (d (ppm), DMSO-d6): 198.97, 198.65 (fac-
Re(CO)3), 178.22 (2C, CO2), 151.87 (C, Ph–OCH3),
139.31 (C, Ph–OCH3), 123.57 (CH, Ph–OCH3), 120.86
(CH, Ph–OCH3), 118.39 (CH, Ph–OCH3), 111.93 (CH,
Ph–OCH3), 66.03 (C, OCH3), 62.75 (2C, CH2CO2),
55.39 (2C, ppz), 52.99 (C, CH2N), 51.46 (2C, ppz), 47.11
(C, NCH2), 19.23 (C, CH2). Mass spectrum (ESIMS):
m=z ¼ ([Re(CO)3(L5)]+Na)þ ¼ 658.0. m=z ¼ ([Re(CO)3
(L5)]+2Na)þ ¼ 680.2. IR (KBr, m/cmꢂ1): 2021, 1880
(m(fac-Re(CO)3)), 1654 (mas(C@O)), 1245 (msym(C@O)) of
the acid group.
2.20.4. [Re(CO)3(L3)]BrCl ꢀ H2O (9BrCl ꢀ H2O)
Yield: 70%. Anal. Calc. for C25H30BrClN5O4ReS2: C,
36.17; H, 3.64; N, 8.44. Found: C, 36.25; H, 3.55; N,
8.20%. 1H NMR (d (ppm), DMSO-d6): 7.96 (d, 2H, Th),
7.88 (d, 2H, Th), 6.97 (m, 4H, Ph–OCH3), 5.28 (d, 2H,
CH2Th), 4.99 (d, 2H, CH2Th), 3.91 (m, 2H, CH2N),
3.80 (s, 3H, OCH3), 3.56 (m, 4H, ppz), 3.35 (m, 4H,
ppz), 3.05 (m, 2H, NCH2), 2.27 (m, 2H, CH2). 13C
NMR (d (ppm), DMSO-d6): 195.66, 193.66 (fac-Re
(CO)3), 173.60 (2C, Th), 151.86 (C, Ph–OCH3), 142.61
(2CH, Th), 141.50 (C, Ph–OCH3), 125.06 (CH, Ph–
OCH3), 120.87 (CH, Ph–OCH3), 119.78 (CH, Th),
118.29 (CH, Ph–OCH3), 111.14 (CH, Ph–OCH3), 63.31
(C, OCH3), 56.22 (2C, ppz), 55.93 (C, NCH2), 53.51
(2C, ppz), 51.35 (C, CH2N), 46.85 (2C, CH2Th), 27.33
(C, CH2). IR (KBr, m/cmꢂ1): 2030, 1921 (m(fac-Re
2.20.7. [Re(CO)3(L6)]Br2 (12Br2)
Yield: 75%. Anal. Calc. for C28H35Br2N6O4Re: C,
38.85; H, 4.08; N, 9.71. Found: C, 38.99; H, 4.12; N,
1
9.56%. H NMR (d (ppm), CDCl3): 8.61 (d, 1H, Py),
7.97 (d, 1H, Py), 7.88 (t, 1H, Py), 7.25 (t, 1H, Py), 6.99–
6.83 (m, 5H, Ph–OCH3, Im), 6.74 (d, 1H, Im), 5.83 (d,
1H, CH2Py), 5.69 (d, 1H, CH2Py), 4.30 (m, 2H,
CH2Im), 3.85 (s, 3H, OCH3), 3.80 (m, 2H, CH2N), 3.76
(s, 3H, NCH3), 3.09 (m, 4H, ppz), 2.73 (m, 4H, ppz),
2.54 (m, 2H, NCH2), 2.25 (m, 2H, CH2). 13C NMR (d
(ppm), CDCl3): 196.39, 196.05, 195.22 (fac-Re(CO)3),
159.48 (C, Py), 152.35 (C, Im), 151.64 (CH, Py), 151.22
(C, Ph–OCH3), 141.30 (C, Ph–OCH3), 140.39 (CH, Py),
127.66 (CH, Ph–OCH3), 125.60 (CH, Py), 125.54 (CH,
Py), 123.87 (CH, Im), 123.07 (CH, Ph–OCH3), 121.07
(CH, Ph–OCH3), 118.31 (CH, Im), 111.31 (CH, Ph–
OCH3), 69.30 (C, CH2N), 68.30 (C, CH2Py), 57.43 (C,
CH2Im), 55.50 (C, OCH3), 55.31 (C, NCH2), 53.67 (2C,
ppz), 50.72 (2C, ppz), 35.87 (C, NCH3), 23.72 (C, CH2).
IR (KBr, m/cmꢂ1): 2025, 1930, 1902 (m(fac-Re(CO)3)).
Mass spectrum (ESIMS): m=z ¼ [Re(CO)3 (L6)]þ ¼
705.2. Cyclic voltammetry (Epa(II/I)): 1.00 V.
(CO)3)).
Mass
spectrum
(ESIMS):
m=z ¼ [Re
(CO)3(L3)]þ ¼ 714.1.
2.20.5. [Re(CO)3(L4)]Br2 (10Br2)
Yield: 72%. Anal. Calc. for C37H38Br2N5O4Re: C,
46.16; H, 3.98; N, 7.27. Found: C, 46.07; H, 4.13; N,
1
7.24%. H NMR (d (ppm), CDCl3): 8.27 (m, 4H, Qu),
7.71 (m, 6H, Qu), 7.49 (t, 2H, Qu), 6.87–6.71 (m, 4H,
Ph–OCH3), 5.47 (d, 2H, CH2Qu), 5.23 (d, 2H, CH2Qu)
3.89 (m, 2H, CH2N), 3.71 (s, 3H, OCH3), 3.14 (m, 8H,
ppz), 2.97 (t, 2H, NCH2), 2.52 (m, 2H, CH2). 13C NMR
(d (ppm), CDCl3): 195.48, 193.87 (fac-Re(CO)3), 164.43
(2C, Qu), 151.95 (C, Ph–OCH3), 146.56 (2C, Qu),
141.35 (2CH, Qu), 139.79 (C, Ph–OCH3), 132.74 (2CH,
Qu), 129.47 (2CH, Qu), 128.09 (2CH, 2C, Qu), 123.42
(CH, Ph–OCH3), 120.78 (CH, Ph–OCH3), 120.17 (3CH,
Qu, Ph–OCH3), 118.20 (CH, Ph–OCH3), 111.17 (CH,
Ph–OCH3), 68.57 (2C, ppz), 65.60 (C, CH2N), 55.27 (C,
OCH3), 54.32 (C, NCH2), 52.87 (2C, ppz), 49.96 (2C,
CH2Qu), 22.35 (C, CH2). IR (KBr, m/cmꢂ1): 2028, 1927,
1908 (m(fac-Re(CO)3)). Mass spectrum (ESIMS):
m=z ¼ [Re(CO)3(L4)]þ ¼ 802.2. Cyclic voltammetry
(Epa(II/I)): 1.03 V.
2.20.8. [Re(CO)3(L7)]BrCl (13BrCl)
Yield: 68%. Anal. Calc. for C26H33BrClN6O4ReS: C,
37.75; H, 4.02; N, 10.16. Found: C, 37.91; H, 3.96; N,
1
10.33%. H NMR (d (ppm), CDCl3): 7.71 (d, 1H, Th),
7.44 (d, 1H, Th), 6.99–6.84 (m, 6H, Ph–OCH3, Im),
4.42–4.15 (m, 4H, CH2Th, CH2Im), 3.85 (d, 6H, OCH3,
NCH3), 3.10 (m, 4H, ppz), 2.73 (m, 4H, ppz), 2.55 (t,
2H, NCH2), 2.24 (m, 2H, CH2N), 1.25 (m, 2H, CH2).
13C NMR (d (ppm), CDCl3): 195.92, 194.39 (fac-Re(-
CO)3), 172.19 (C, Th), 152.38 (C, Im), 151.01 (C, Ph–
OCH3), 142.29 (CH, Th), 141.11 (C, Ph–OCH3), 127.89
(CH, Im), 123.91 (CH, Ph–OCH3), 123.77 (CH, Im),
123.07 (CH, Ph–OCH3), 121.09 (CH, Th), 118.31 (CH,
Ph–OCH3), 111.35 (CH, Ph–OCH3), 69.41 (C, CH2Th),
63.96 (C, CH2Im), 57.98 (C, NCH2), 55.51 (C, OCH3),
55.23 (C, CH2N), 53.68 (2C, ppz), 50.77 (2C, ppz), 36.15
(C, NCH3), 23.86 (C, CH2). IR (KBr, m/cmꢂ1): 2028,
1903 (m(fac-Re(CO)3)). Mass spectrum (ESIMS):
2.20.6.
[Re(CO)3(L5)] ꢀ xCH3OH
(11 ꢀ xCH3OH,
x ꢁ 0:875)
Yield: 66%. Anal. Calc. for C21H26N3O8Re: C, 39.74;
H, 4.13; N, 6.62. Found: C, 39.68; H, 4.21; N, 6.55%. 1H
NMR (d (ppm), DMSO-d6): 6.98 (m, 4H, Ph–OCH3),

L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
1507
m=z ¼ [Re(CO)3(L7)]þ ¼ 711.2. Cyclic voltammetry
(Epa(II/I)): 0.96 V.
3.80 (s, 3H, NCH3), 3.62 (m, 4H, ppz), 3.36–3.12 (m,
8H, ppz, CH2N, NCH2), 2.39 (m, 2H, CH2). 13C
NMR (d (ppm), CD3OD): 198.52, 198.11, 196.91 (fac-
Re(CO)3), 182.37 (C, CO2), 154.16 (C, Im), 151.83 (C,
Ph–OCH3), 140.63 (C, Ph–OCH3), 129.26 (CH, Im),
125.82 (CH, Im), 125.26 (CH, Ph–OCH3), 122.4 (CH,
Ph–OCH3), 120.16 (CH, Ph–OCH3), 113.13 (CH, Ph–
OCH3), 67.49 (C, CH2CO2), 63.85 (C, CH2Im), 59.82
(C, OCH3), 56.19 (2C, NCH2, CH2N), 55.01 (2C,
ppz), 53.38 (2C, ppz), 35.23 (C, CH2), 21.72 (C,
NCH3). IR(KBr, m/cmꢂ1): 2027, 1926, 1870 (fac-Re
(CO)3), 1629 (mas(C@O)), 1245 (msym(C@O)) of the
acid group. Mass spectrum (ESIMS): m=z ¼ [Re(CO)3
(L9)]þ ¼ 672.2.
2.20.9. [Re(CO)3(L8)]BrCl (14BrCl)
Yield: 78%. Anal. Calc. for C27H32Br2N5O4ReS: C,
37.33; H, 3.71; N, 8.06. Found: C, 37.53; H, 3.55; N,
1
7.98%. H NMR (d (ppm), CD3OD): 8.41 (d, 1H, Py),
8.02 (t, 1H, Py), 7.99 (d, 1H, Th), 7.75 (d, 1H, Th),
7.71 (d, 1H, Py), 7.42 (t, 1H, Py), 7.03 (m, 4H, Ph–
OCH3), 5.20, 5.05 (d, d, 4H, CH2Py, CH2Th), 4.01 (m,
2H, CH2N), 3.89 (s, 1H, OCH3), 3.64 (m, 4H, ppz),
3.38 (m, 6H, NCH2, ppz), 2.52 (m, 2H, CH2). 13C
NMR (d (ppm), CD3OD): 196.91, 196.66, 195.57 (fac-
Re(CO)3), 175.42 (C, Th), 161.24 (C, Py), 154.15 (C,
Ph–OCH3), 153.57 (CH, Py), 144.02 (C, Th), 141.95
(C, Ph–OCH3), 140.65 (CH, Py), 127.14 (CH, Py),
125.84 (2C, Ph–OCH3), 125.46 (CH, Py), 122.40 (CH,
Th), 120.17 (CH, Ph–OCH3), 113.15 (CH, Ph–OCH3),
69.57 (C, CH2Th), 67.91 (C, NCH2), 64.35 (C,
CH2Py), 56.22 (C, OCH3), 54.94 (C, CH2N), 54.09
(4C, ppz), 21.84 (C, CH2). IR (KBr, m/cmꢂ1): 2030,
1917, 1891 (m(fac-Re(CO)3)).
2.20.11. [Re(CO)3(L10)]BrCl (16BrCl)
Yield: 76%. Anal. Calc. for C25H31BrClN4O6Re: C,
38.25; H, 3.98; N, 7.14. Found: C, 38.16; H, 4.07; N,
1
7.23%. H NMR (d (ppm), CDCl3): 8.82 (d, 1H, Py),
7.94 (t, 1H, Py), 7.52 (d, 1H, Py), 7.41 (t, 1H, Py), 6.95
(m, 4H, Ph–OCH3), 4.50 (d, 1H, CH2Py), 4.38 (d, 1H,
CH2Py), 3.88 (s, 3H, OCH3), 3.69, (d, 1H, CH2CO2),
3.61 (t, 2H, NCH2), 3.41 (d, 1H, CH2CO2), 3.13 (m, 4H,
ppz), 2.75 (m, 4H, ppz), 2.56 (t, 2H, CH2N), 2.06 (m,
2H, CH2). 13C NMR (d (ppm), CDCl3): 197.65, 197.04,
196.20 (fac-Re(CO)3), 179.09 (C, CO2), 158.49 (C, Py),
152.99 (CH, Py), 152.41 (C, Ph–OCH3), 141.14 (C, Ph–
OCH3), 140.10 (CH, Py), 126.06 (CH, Py), 123.39 (CH,
Ph–OCH3), 123.33 (CH, Py), 121.19 (CH, Ph–OCH3),
118.45 (CH, Ph–OCH3), 111.38 (CH, Ph–OCH3), 68.88
(C, CH2Py), 68.25 (C, CH2CO2), 61.69 (C, NCH2),
2.20.10. [Re(CO)3(L9)]BrCl ꢀ 1.5CH3OH ꢀ H2O (15Br-
Cl ꢀ 1.5CH3OH ꢀ H2O)
Yield: 80%. Anal. Calc. for C24H32BrClN5O6Re: C,
36.58; H, 4.09; N, 8.89. Found: C, 36.77; H, 3.98; N,
1
9.01%. H NMR (d (ppm), CD3OD): 7.22 (d, 1H, Im),
7.14 (d, 1H, Im), 7.13–6.92 (m, 4H, Ph–OCH3), 4.72
(d, 1H, CH2Im), 4.47 (d, 1H, CH2Im), 3.96 (d, 1H,
CH2CO2), 3.71 (d, 1H, CH2CO2), 3.88 (s, 3H, OCH3),
Table 1
Summary of crystal data
6Br ꢀ H2O
18Br
17Br
11 ꢀ xCH3OH
7Br2 ꢀ 2CH2Cl2 ꢀ H2O 15BrCl ꢀ 1.5CH3OH ꢀ
H2O
Formula
Formula
weight
Space
C
590.49
15H24BrN4O4Re C19H22BrFN5O3Re C21H23BrFN4O3Re C43:75H59N6O17:75Re2 C31H40Br2Cl4N5O5Re C25:5H39BrClN5O8:5Re
853.18
653.53
664.54
1325.37
1050.50
P21=c
P21=c
P21=c
Cc
P21=c
P1
group
T (K)
90(2)
90(2)
90(2)
90(2)
90(2)
90(2)
ꢀ
a (A)
7.3565(5)
33.397(2)
8.1325(5)
90
15.345(3)
11.076(2)
13.105(3)
90
11.344(1)
14.433(1)
13.730(1)
90
20.321(1)
22.754(1)
12.0679(6)
90
30.015(1)
8.9324(4)
14.7361(6)
90
11.818(1)
13.292(1)
14.5167(8)
63.915(2)
66.373(2)
67.416(2)
1815.6(4)
2
ꢀ
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
108.990(1)
90
99.05(3)
90
103.092(2)
90
115.429(1)
90
103.195(1)
90
3
ꢀ
V (A )
1889.3(2)
4
2.076
2199.6(8)
4
1.973
2189.5(3)
4
2.016
5039.5(5)
4
1.747
3846.5(3)
4
1.814
Z
Dcalc
(g cmꢂ3
1.561
)
l (mmꢂ1
R1 (all
data)
)
8.574
0.0564
7.379
0.0375
7.414
0.0256
4.876
0.0792
5.559
0.0627
4.568
0.0709
a
a
wR2
0.0810
0.0716
h
0.0502
0.1068
0.0872
0.1003
i
1=2
P
P
P
P
2
2
a R1 ¼ jjFoj ꢂ jFcjj= jFoj; wR2 ¼
wðFo2 ꢂ Fc2Þ = wðFo2Þ
.

1508
L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
55.57 (2C, ppz), 55.35 (C, OCH3), 53.64 (2C, ppz), 50.60
(C, CH2N), 22.93 (C, CH2). IR(KBr, m/cmꢂ1): 2023,
1891 (fac-Re(CO)3), 1654 (mas(C@O)), 1120 (msym(C@O))
of the acid group. Mass spectrum (ESIMS): m=z ¼
[Re(CO)3(L10)]þ ¼ 669.3.
2.20.12. [Re(CO)3(L11)]Br (17Br)
Yield: 80%. Anal. Calc. for C21H23BrFN4O3Re: C,
37.95; H, 3.49; N, 8.43. Found: C, 38.06; H, 3.37; N,
1
8.38%. H NMR (d (ppm), CDCl3): 8.73 (d, 1H, Py),
8.09 (t, 1H, Py), 7.96 (m, 2H, Py, NH), 7.47 (t, 1H, Py),
7.01 (m, 4H, Ph–F), 5.07 (d, 1H, CH2Py), 4.70 (d, 1H,
CH2Py), 3.80–2.47 (m, 12H, ppz, NCH2, CH2NH). 13C
NMR (d (ppm), CDCl3): 196.40, 195.18, 191.85 (fac-
Re(CO)3), 162.39 (C, Py), 156.93 (CH, Py), 153.67 (C,
Ph–F), 152.05 (CH, Py), 140.68 (CH, Py), 138.20 (C,
Ph–F), 125.75 (CH, Py), 124.57 (CH, Ph–F), 123.98
(CH, Ph–F), 119.08 (CH, Ph–F), 116.00 (C, Ph–F),
62.73 (C, CH2N), 60.49 (C, CH2Py), 57.79 (2C, ppz),
57.30 (2C, ppz), 49.68 (C, CH2N). IR (KBr, m/cmꢂ1):
3004, (m
(mðbendÞ(NH)), 726 (m(C–F)).
(NH)); 2022, 1888 (m(fac-Re(CO)3)); 1236
ðstÞ
2.20.13. [Re(CO)3(L12)]Br (18Br)
Yield: 74%. Anal. Calc. for C19H22BrFN5O3Re: C,
34.92; H, 3.39; N, 10.72. Found: C, 35.11; H, 3.29; N,
1
10.66%. H NMR (d (ppm), CDCl3): 7.48 (d, 1H, Im),
7.19 (d, 1H, Im), 7.06–6.96 (m, Ph–F), 4.77 (d, 1H,
CH2Im), 4.58 (d, 1H, CH2Im), 3.67–2.94 (m, 10H, ppz,
CH2N), 2.50–2.34 (m, 2H, NCH2). 13C NMR (d (ppm),
CDCl3): 196.25, 196.08, 192.25 (fac-Re(CO)3), 157.33
(C, Im), 154.07 (C, Ph–F), 153.00 (C, Ph–F), 138.62
(CH, Im), 127.85 (CH, Ph–F), 124.86 (CH, Ph–F),
120.58 (CH, Im), 116.51 (CH, Ph–F), 116.41 (CH, Ph–
F), 62.63 (C, CH2N), 58.05 (C, NCH2), 52.60 (C,
CH2Im), 52.25 (2C, ppz), 47.77 (2C, ppz). IR (KBr, m/
cmꢂ1): 2025, 1893 (m(fac-Re(CO)3)), 1240 (mðbendÞ(NH)),
721 (m(C–F)).
2.20.14. [Re(CO)3(L13)] (19)
Yield: 60%. Anal. Calc. for C23H26FN4O3ReS: C,
42.91; H, 4.07; N, 8.70. Found: C, 43.10; H, 3.99; N,
8.87%. 1H NMR (d (ppm), CDCl3: 8.62 (d, 1H, Py), 7.82
(t, 1H, Py), 7.41 (m, 2H, Py), 7.12–6.88 (m, 4H, Ph–F),
4.68 (d, 1H, CH2Py), 4.48 (dd, 1H, CH2Py), 3.85 (m,
1H, CH2N), 3.61 (m, 1H, CH2N), 3.13 (m, 4H, ppz),
3.00 (m, 2H, NCH2), 2.88 (t, 2H, ppz-NCH2), 2.74 (m,
4H, ppz), 2.6 (m, 1H, CH2S), 1.74 (m, 1H, CH2S) 13C
NMR (d (ppm), CDCl3: 199.40, 198.52, 195.21 (fac-
Re(CO)3), 159.28 (C, Py), 155.00 (C, Ph–F), 153.48
(CH, Py), 140.01 (C, Ph–F), 138.40 (C, CH, Py), 125.70
(C, CH, Py), 124.70 (CH, Ph–F), 122.91 (C, Ph–F),
120.71 (CH, Py), 119.14 (CH, Ph–F), 116.38 (CH, Ph–
F), 68.37 (C, CH2Py), 67.98 (C, NCH2), 64.37 (C,
CH2N), 54.96 (C, ppz-NCH2), 53.83 (2C, ppz), 50.73
(2C, ppz), 28.00 (C, CH2SH). IR (KBr, m/cmꢂ1): 2024,

L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
1509
1898 (m(fac-Re(CO)3)); 726 (mC–F). Mass spectrum
(ESIMS): m=z ¼ ([Re(CO)3(L13)]+1)þ ¼ 644, m=z ¼ ([Re
(CO)3(L13)]+1-CO)þ ¼ 616.
scription of the details of the crystallographic methods
is given in the Supporting Information.
2.21. X-ray crystal structure determinations of complexes
6Br ꢀ H2O, 7Br2 ꢀ 2CH2Cl2 ꢀ H2O, 11 ꢀ xCH3OH, 15Br-
Cl ꢀ 1.5CH3OH ꢀ H2O, 17Br and 18Br
3. Results and discussion
3.1. Ligand syntheses
The selected crystals of the complexes were studied
on a Bruker diffractometer equipped with the SMART
CCD system [30], using graphite-monochromated Mo
The ligand syntheses are summarized in Schemes 2–5.
The ligand L1 was prepared by the treatment of meth-
oxyphenylpiperazine with N-(3-bromopropyl)phthali-
mide followed by hydrolysis of the phthalimide group
with hydrazine hydrate. The free amine was reacted with
two equivalents of 2-chloromethylpyridine in basic so-
lution to give L1 (Scheme 2).
Several other dialkylated phenylpiperazine derivatives
(ligands L2–L5) were prepared using direct reductive
alkylation of the methoxyphenyl-piperazine-propyl-
amine with the appropriate aldehydes. The reactions
were performed in 1,2-dichloroethane (DCE) (Scheme 2)
using sodium triacetoxyborohydride as a robust and
effective reducing reagent. In comparison to the method
used to prepare ligand L1, the advantages of the reduc-
tive amination of aldehydes with sodium triaceoxy-
borohydride (NaBH(OAc)3) include shorter time, easier
work-up and higher yield.
ꢀ
Ka radiation (k ¼ 0:71073 A). The data collections
were carried out at 90(5) K. The data were corrected
for Lorentz polarization effects and absorption cor-
rections were made using SADABS [31]. All calculations
were performed using SHELXTL [32]. The structures
were solved by direct methods and all of the non-
hydrogen atoms were located from the initial solution.
After locating all the non-hydrogen atoms in the
structure, the model was refined against F 2, initially
using isotropic and later anisotropic thermal displace-
ment parameters until the final value of D=rmax was
less than 0.001. At this point the hydrogen atoms were
located from the electron density difference map and a
final cycle of refinements was performed, until the final
value of D=rmax was again less than 0.001. No anom-
alies were encountered in the refinement of the struc-
ture. The relevant parameters for crystal data, data
collection, structure solution and refinement are sum-
marized in Table 1, and important bond lengths and
bond angles are presented in Table 2. A complete de-
Mixed dialkylated derivatives of the arylpiperazines
(ligands L6–L8) were also prepared. Methoxyphenyl-
piperazine-propylamine (1) was refluxed with 1-methyl-2-
imidazolecarboxaldehyde or 2-pyridinecarboxaldehyde
in methanol to give Schiff base intermediates, which were
Scheme 2.

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L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
Scheme 3.
Scheme 4.
reduced by NaBH4 to give {3-[4-(2-methoxyphenyl)-
piperazin-1-yl]-propyl}-(1-methyl-1H-imidazol-2-ylm-
ethyl)-amine (2) or {3-[4-(2-methoxy-phenyl)-piperazin-
1-yl]-propyl}-pyriin-2-ylmethyl-amine (3). The amines 2
and 3 were reacted with heterocyclic aldehydes using
NaBH(OAc)3 to give ligands L6, L7 and L8 (Scheme 3).
Ligand L9 was prepared from amine 2 by reactions
with benzyl-2-bromoacetate followed by hydrogenation
(Scheme 4). Ligand L10 was isolated by reacting amine 3
with glyoxylic acid using NaBH(OAc)3 as the reducing
agent (Scheme 4). Again, the direct reductive amination
reaction has considerable advantages compared to other
preparative procedures for L9.
Using a similar procedure, the fluorophenylpiper-
azine derivatives L11, L12 were prepared by treatment
of fluorophenylpiperazine with N-(2-bromoethyl)phth-

L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
1511
Scheme 5.
alimide, followed by reaction with 2-pyridinecarboxy-
aldehyde or 2-imidazolecarboxyaldehyde. L11 was re-
acted with ethylene sulfide to yield L13 (Scheme 5).
peaks attributed to bending vibrations of the N–H
bonds around 1240 cmꢂ1 [37].
1H and 13C NMR spectroscopy indicate that the
complexes retain their solid-state structures in solution.
The assignments of all protons and carbons in all the
ligands and the corresponding complexes are based on
intensity, spin–spin splitting structure, 1H–1H COSY
3.1.1. Syntheses of the rhenium complexes and their
spectroscopic properties
All complexes were prepared in excellent yields by
reacting equivalent amounts of the appropriate ligand
and (NEt4)2[Re(CO)3Br3] in methanol for a few hours.
Single crystals suitable for X-ray crystallography were
obtained by slow diffusion of hexane into solutions of
the complexes in dichloromethane.
1
and H–13C HMQC experiments and are presented in
Section 2. Complexes 7–11 exhibit mirror symmetry
with the mirror plane passing through one of the three
facial carbonyl groups and the aliphatic amine. This
1
feature is reflected in the H NMR spectra: the proton
The infrared spectra of the complexes 6–19 exhibit
strong bands in the 2030–1888 cmꢂ1 range, attributed to
m(C–O) of the fac-{Re(CO)3} unit [33–36]. The com-
plexes 11, 15, 16 show two strong absorptions in the
1654–1629 and 1245–1120 cmꢂ1 ranges, corresponding
to vibrations of the carboxylic acid group, mas(CO2) and
signals of methylene groups adjacent to the aromatic
groups or the carboxylic acid groups are split into two
sets of doublets with coupling constants consistent with
geminal coupling (16–20 Hz). The 13C NMR spectra of
the complexes reveal that there are only two Re–CO
peaks in the 198–193 ppm range. The characteristic 2:1
peak height for these carbonyl resonances indicates that
the two CO groups are magnetically equivalent because
of the mirror symmetry. Also, there is only one set of
m
sym(CO2), respectively. The complexes 17, 18, 19 exhibit
peaks at ca. 726 cmꢂ1, assigned to bending vibrations of
the C–F bonds. The complexes 17 and 18 also show

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L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
Fig. 1. 1H–1H COSY and 1H–13C HMQC spectra of [Re(CO)3(L13)] (19) in CDCl3 at room temperature.
aromatic proton and carbon signals for complexes 7–11,
consistent with the mirror symmetry. On the other hand,
complexes 12–18 do not possess mirror symmetry, and
NMR signals. The proton signal of the methylene group
adjacent to the pyridine is split into two sets of doublets
observed in the 4.68–4.48 ppm range. The proton peaks
of the methylene groups adjacent to the aliphatic amine
and the sulfur atom are split into two sets of multiplets
in the regions 3.85–3.61 and 2.60–1.74 ppm, respec-
tively.
The data obtained from the electrospray ionization
mass spectra of the complexes are consistent with the
formulations from the elemental analysis and from
the spectroscopic evidence. For most of the complexes,
the highest m=z peaks are assigned to the [Re(CO)3(L)]þ
parent ions on the basis of the isotopic distribution of
185; 187Re. The highest m=z peak of complex 11 occurs at
658 and is assigned to (11+Na)þ. In addition, a m=z
peak at 680 corresponds to (11+2Na)þ. The mass
spectrum of complex 19 displays a m=z peak at 644,
1
the H and 13C NMR spectra are consequently quite
distinct from those of complexes 7–11. The proton sig-
nals of the methylene groups adjacent to the aromatic
groups or the carboxylic acid groups are split into four
sets of doublets. The splitting patterns in certain in-
stances overlap so that only multiplet signals were ob-
served. 13C NMR spectra of complexes 12–18 show
three peaks with equal intensity in the 198–193 ppm
range as expected for the unsymmetrical fac-{Re
(CO)3}þ moiety.
The NMR spectra of complex 19 are more compli-
cated due to the splitting of all methylene protons. Us-
1
1
ing H–1H COSY and H–13C HMQC NMR spectra
(Fig. 1), we were able to assign all H NMR and 13C
1

L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
1513
assigned to (19+H)þ. Another m=z peak at 616 corre-
sponds to (19+H–CO)þ.
than those of complexes 8 and 13, consistent with the
stronger electron withdrawing power of pyridyl group
compared to that of the N-methylimidaozolyl and
thiazolyl group. The more positive Epa value of complex
10, compared to complex 7, is related to more effective
conjugation by the quinolinyl group than by the pyridyl
group.
3.2. Electrochemistry
The electrochemical behavior of selected complexes
was studied in acetonitrile solution under the conditions
described in Section 2. The complexes show irreversible
oxidation waves in the range +0.96 to +1.03 V, which
can be assigned to the ReI/ReII process. The anodic
waves are irreversible suggesting that the ReII complexes
are unstable. The redox behavior is similar to that of
previously reported examples of ReI/ReII couples for the
{Re(CO)3}þ core [38–44]. In the cathodic scan, no re-
ductive processes were observed.
3.3. Crystallographic studies
The structure of the model compound [Re
(CO)3 {(CH3N2C3H2CH2)N(H)CH2CH2-piperidine}]Brꢀ
The oxidative potential values of the complexes 7, 8,
10, 12 and 13 are consistent with substituent effects, al-
though the differences between the Epa values are small.
The Epa values of complexes 7 and 12 are more positive
Fig. 2. A view of the structure of the molecular cation of [Re(-
CO)3(L14)]Br ꢀ H2O (6Br ꢀ H2O), showing the atom-labeling scheme
and 50% probability ellipsoids.
Fig. 3. A view of the structure of the molecular cation of [Re(-
CO)3(L12)]Br (18Br), showing the atom-labeling scheme and 50%
probability ellipsoids.
Fig. 4. A view of the structure of the molecular cation of [Re(CO)3(L11)]Br (17Br), showing the atom-labeling scheme and 50% probability ellipsoids.

1514
L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
2
ꢀ
amine nitrogens (Re–N, 2.210 and 2.316 A), the sp
H2O (6Br ꢀ H2O), shown in Fig. 2, reveals that ligands
monoalkylated at the amine nitrogen will adopt triden-
tate coordination through the alkylated nitrogen of the
piperidine or piperazine ring. The Re(I) site is coordi-
nated to three carbonyl donors in a facial arrangement
and to the imidazole nitrogen, the amine nitrogen of the
ligand arm and the piperidine ring nitrogen to give
{Re(CO)3N3} coordination. The distortions from ide-
alized octahedral geometry reflect the multiple bond
ꢀ
character of the imidazole nitrogen (Re–N, 2.148 A) and
the steric constraints imposed by the five-membered
chelate rings (Re(1)–N(1)–C(6)–C(8)–N(2) and Re(1)–
N(3)–C(10)–C(9)–N(2)).
The structure of [Re(CO)3{(CH3N2C3H2CH2)N(H)
CH2CH2-Fphenpip}]Br(18Br) exhibits a discrete Br
anion and the [Re(CO)3{(CH3N2C3H2CH2)N(H)CH2-
CH2-Fphenpip}]þ molecular cation. As shown in Fig. 3,
the structure of the cation of 18 is similar to that of 6,
with the exception that the fluorophenylpiperazine
ꢀ
character of the carbonyl groups (Re–C, 1.912 A; C–O,
3
ꢀ
1.155 A), the single bond character of the sp hybridized
Fig. 5. A view of the structure of the complex of [Re(CO)3(L5)] ꢀ xCH3OH (11 ꢀ xCH3OH), showing the atom-labeling scheme and 50% probability
ellipsoids.
Fig. 6. (a) A view of the structure of the molecular cation of [Re(CO)3(L1)] Br2 ꢀ 2CH2Cl2 ꢀ H2O (7Br2 ꢀ 2CH2Cl2 ꢀ H2O), showing the atom-labeling
scheme and 50% probability ellipsoids. (b)
A
view of the structure of the molecular cation of [Re(CO)3(L9)]BrCl ꢀ 1.5CH3OH ꢀ H2O
(15BrCl ꢀ 1.5CH3OH ꢀ H2O), showing the atom-labeling scheme and 50% probability ellipsoids.

L. Wei et al. / Inorganica Chimica Acta 357 (2004) 1499–1516
1515
group is present in place of the piperidine subunit of 6.
The coordination geometry at the Re(I) site is again
{Re(CO)3N3} with bond distances similar to those ob-
served for 6Br.
The structure of 18Br may be compared to that of
[Re(CO)3{(NC5H4CH2)N(H)CH2CH2-Fphenpip}]Br
(17Br). As shown in Fig. 4, the structure of the mo-
lecular cation 17þ displays {Re(CO)3N3} geometry,
with the imidazole nitrogen of 18Br replace by a
pyridyl donor. The metrical parameters for the Re(I)
site are similar to those of 18Br (Table 2).
(CH2)nN(CH2Y)(CH2Z). Since the donor groups may
be neutral, anionic or a combination of neutral and
anionic, {M(CO)3L3}n coordination complexes with
charges of +1, 0 or )1 may be prepared. Curiously, the
tendency of the piperazine nitrogen sites to undergo
protonation has limited the solid state materials to
neutral and cationic core complexes.
5. Supporting information available
The structure of [Re(CO)3{(O2CCH2)2NCH2CH2-
CH2-CH3OphenpipH}] ꢀ xCH3OH (11 ꢀ xCH3OH, x ꢁ
0:875) reveals the consequences of dialkylation of the
amine nitrogen and the introduction of negatively
charged carboxylate donor groups. The neutral molec-
ular unit 11 displays {Re(CO)3NO2} coordination ge-
ometry, shown in Fig. 5. The Re–CO and Re–N amine
bond distances are unexceptional (Table 2), and the Re–
Tables of complete crystal data, final coordinates,
temperature factors, distances and angles for the crys-
tallographic study of 6Br ꢀ H2O, 7Br2 ꢀ 2CH2Cl2 ꢀ H2O,
11 ꢀ xCH3OH, 15BrCl ꢀ 1.5CH3OH ꢀ H2O, 17Br and 18Br
in CIF format have been deposited at the Cambridge
Crystallographic Data Centre, CCDC Nos. 223512–
223517, respectively. Copies of the CIF files are avail-
able from the Director, CCDC, 12 Union Road, Cam-
bridge, CB2 1EZ, UK (fax: +44-1223-336-033; email:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
ꢀ
O distances are 2.120(8) and 2.134(6) A. The complex
attains charge neutrality by protonation of the N2 site.
The structure of 11 ꢀ xCH3OH is prototypical of
{Re(CO)3}þ cores with the amine groups dialkylated to
provide tridentate chelators. As shown in Fig. 6, the
structures of [Re(CO)3{(NC5H4CH2)2NCH2CH2CH2-
CH3OphenpipH}]Br2 ꢀ 2CH2Cl2 ꢀ H2O (7Br2 ꢀ 2CH2Cl2 ꢀ
H2O) and [Re(CO)3{(CH3N2C3H2CH2)(O2CCH2)NC-
H2CH2CH2-CH3OphenpipH2}]BrCl ꢀ 1.5CH3OH ꢀ H2O
(15BrCl ꢀ 1.5CH3OH ꢀ H2O) display {Re(CO)3N3} and
{Re(CO)3N2O} coordination geometries, respectively.
In the case of 72þ, the {Re(CO)3}þ core bonds to two
pyridyl nitrogen donors and the amine donor, while in
152þ, the core is coordinated to an imidazole nitrogen, a
carboxylate oxygen, and the amine donor. The charge of
the cation 72þ is a consequence of protonation of the
alkylated piperazine nitrogen site N4, while the charge
of 152þ requires protonation of both piperazine nitrogen
sites, N4 and N5.
Acknowledgements
This work was supported by a grant from the De-
partment of Energy (DOE), Office of Health and Envi-
ronmental Research D2-FG02-99ER62791.
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