Re(I)(tricarbonyl)(carboxylate) complexes with the [N,N′-bis(2,4,6-trimethylbenzene)-1,4-diazabutadiene] (2,4,6-Me3G) and [N,N′-bis(2,4-dimethylbenzene)-2,3-dimethyl-1,4-diazabutadiene] (2,4-Me2D) ligands - Syntheses and spectroscopic studies. The crystal structure of [Re(CO)3(2,4,6-Me3G)(OCOCF3)]

Article abstract of DOI:10.1016/j.poly.2007.01.043

Two new carboxylato complexes, [Re(CO)₃(DAB)(OCOCF₃)] (DAB = substituted aromatic diazabutadiene ligands), were prepared by the reaction of [Re(CO)₅Cl] with the DAB ligands, and the subsequent reaction with AgOCOCF₃ gave the related carboxylate complexes. These new complexes were characterized by FTIR, NMR, UV-Vis spectra and elemental analysis. In both complexes, the Re atom has a distorted octahedral configuration and is coordinated by two carbonyl groups and the diimine group of the organic ligand in the equatorial plane. Octahedral coordination is completed at the axial positions by another carbonyl ligand and a carboxyl O atom of the trifluoroacetate anion. Electrochemical behaviour of the investigated complexes has been studied by cyclic voltammetry.

Full text of DOI:10.1016/j.poly.2007.01.043

Polyhedron 26 (2007) 2906–2910
www.elsevier.com/locate/poly
Re(I)(tricarbonyl)(carboxylate) complexes with the
[N,N0-bis(2,4,6-trimethylbenzene)-1,4-diazabutadiene] (2,4,6-Me3G)
and [N,N0-bis(2,4-dimethylbenzene)-2,3-dimethyl-1,4-diazabutadiene]
(2,4-Me2D) ligands – Syntheses and spectroscopic studies.
The crystal structure of [Re(CO)3(2,4,6-Me3G)(OCOCF3)]
a
a,
b
b,
*
*
´
´
´
Reza Kia , Valiollah Mirkhani , Alajos Kalman , Andrea Deak
a
Department of Chemistry, University of Isfahan, Isfahan 81746-73441, Iran
Institute of Structural Chemistry, Chemical Research Center of the Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 17, Hungary
b
Received 6 January 2007; accepted 27 January 2007
Available online 7 February 2007
Abstract
Two new carboxylato complexes, [Re(CO)3(DAB)(OCOCF3)] (DAB = substituted aromatic diazabutadiene ligands), were prepared
by the reaction of [Re(CO)5Cl] with the DAB ligands, and the subsequent reaction with AgOCOCF3 gave the related carboxylate com-
plexes. These new complexes were characterized by FTIR, NMR, UV–Vis spectra and elemental analysis. In both complexes, the Re
atom has a distorted octahedral configuration and is coordinated by two carbonyl groups and the diimine group of the organic ligand
in the equatorial plane. Octahedral coordination is completed at the axial positions by another carbonyl ligand and a carboxyl O atom of
the trifluoroacetate anion. Electrochemical behaviour of the investigated complexes has been studied by cyclic voltammetry.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Rhenium(I) complexes; Diazabutadiene ligand; X-ray crystal structure
1. Introduction
in the selective reduction of CO2 [6], a process of interest in
the conversion and storage of solar energy, and serve as
models for natural photosynthesis [7,8]. Control of the
excited state resulting from metal-to-ligand charge transfer
(MLCT) and the redox properties of these complexes,
through structural and electronic modifications in the
a-diimine chelate and/or axial ligands, has been proposed
as a way to improve the photo- and electrocatalytic prop-
erties of these compounds. Therefore, knowledge of the
molecular and crystal structure of such complexes is essen-
tial for understanding and explaining their properties. Sig-
nificant research has focused on common chelating ligands
such as bipyridine (bpy) and phenanthroline (phen), but
the chemistry of the fac-[Re(CO)3(X)] complexes with other
bidentate a-diimine ligands remains largely unexplored.
Bearing in mind all the above mentioned facts, we decided
to pursue studies on the fac-[Re(CO)3(DAB)(OCOCF3)]
The d6 transition metal Re(I), Ru(II), Os(II) or Rh(III)
complexes with a-diimine ligands have been the subject of
intense investigations [1–4]. Complexes of the type
[Re(CO)3(a-diimine)(X)]0/+, in which X is a halide, bridg-
ing ligand, organic donor/acceptor, nitrogen donor or
some other monodentate ligand, have been the subject of
a large number of studies. Furthermore, this permanently
growing interest stems from the ability of these complexes
and their reduced form to act as efficient sensitizers for
energy and electron transfer processes [5], and as catalysts
*
Corresponding authors. Tel.: +98 311 7932713; fax: +98 311 6689732
´
(V. Mirkhani); tel.: +36 1 325 7547; fax: +36 1 438 4141/327 (A. Deak).
E-mail addresses: mirkhani@sci.ui.ac.ir (V. Mirkhani), deak@chemre-
´
s.hu (A. Deak).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.01.043

R. Kia et al. / Polyhedron 26 (2007) 2906–2910
2907
Table 1
complexes in which DAB = [N,N-bis(2,4,6-trimethylben-
Crystal data and structure refinement parameters for complex 1
zene)-1,4-diazabutadiene] (2,4,6-Me3G), and [N,N-bis(2,
4-dimethylbenzene)-2,3-dimethyl-1,4-diazabutadiene] (2,4-
Me2D). To the best of our knowledge, these complexes
are the first reported Re(I)(tricarbonyl) carboxylate com-
plexes with aromatic diazabutadiene ligands which were
characterized by X-ray diffraction analysis, and the com-
plex [Re(CO)3(2,4-Me2D)(OCOCF3)] is the first metal
complex containing the N,N-bis(2,4-dimethylbenzene)-2,3-
dimethyl-1,4-diazabutadiene ligand. The crystal structure
of [Re(CO)3(2,4-Me2D)(OCOCF3)] has been reported else-
where [9].
Complex
1
Empirical formula
Formula mass
C25H24F3N2O5Re
675.66
Crystal size (mm)
Colour
0.51 · 0.52 · 0.62
dark-red
Crystal system
Space group
monoclinic
P21/c
h Range for data collection (ꢁ)
a (A)
3.0 6 h 6 27.5
8.162(3)
˚
˚
b (A)
13.581(4)
24.456(9)
˚
c (A)
b (ꢁ)
V (A )
Z
Dcalc (Mg/m3)
l (mmꢀ1
F(000)
105.07(2)
2617.7(16)
4
1.714
4.700
3
˚
2. Experimental
)
2.1. General
1320
Index ranges
ꢀ10 6 h 6 10, ꢀ16 6 k 6 17,
ꢀ31 6 l 6 31
20168
All chemicals used were reagent grade and were used as
received. Solvents used for the reactions were purified by
literature methods [10]. The diazabutadiene ligands were
prepared according to a modified literature procedure
[11]. NMR spectra were obtained on a Bruker Avance
DRX500 (500 MHz) spectrometer. The chemical shifts (d)
are reported in part per million (ppm) relative to an inter-
nal standard of Me4Si. The UV–Vis spectra were recorded
on a Shimadzu UV-160 spectrophotometer with quartz
cells (1 cm path length). Elemental analyses were per-
formed using a Heraeus elemental analyzer. IR spectra
were recorded as KBr pellets on a Nicolet Impact 400D
spectrophotometer. Electrochemical data were obtained
by cyclic voltammetry (CV) with a three-electrode cell con-
taining an Ag/AgCl reference electrode, a Pt wire counter
electrode and a Pt working electrode. A Metrohm multi-
purpose instrument model 757 was used. CV measurements
were performed in CH2Cl2 with 25 mM of Bu4NClO4
(TBAP) as a supporting electrolyte. In all electrochemical
experiments, the solutions were purged with Ar gas for at
least 5 min.
Number of collected reflections
Number of independent
reflections/Rint
Number of observed reflections
I > 2r(I)
Number of parameters
Goodness-of-fit (GOF)
R1 (observed data)
wR2 (all data)a
5627/0.045
4644
331
1.06
0.0322
0.0710
2
2
a
w ¼ 1=½r2ðF oÞ þ ð0:0094PÞ þ 8:4642Pꢁ where P ¼ ðF o2 þ 2F 2c Þ=3.
tion of SHELXL). The carbon atoms of the benzene rings
were refined with distance restraints (SADI 0.002 instruc-
tion of SHELXL). All non-hydrogen atoms were refined
anisotropically in the F2 mode. Hydrogen atoms were con-
strained to idealized geometries and refined isotropically.
The riding model was applied for the hydrogen atoms. In
addition, the riding methyl hydrogen atoms were allowed
to rotate freely during refinement.
2.2. X-ray crystallography
2.3. Synthesis
Suitable single crystals of [Re(2,4,6-Me3G)(CO)3(O-
COCF3)] (1) were obtained by diffusion of n-hexane vapour
into a CH2Cl2 solution at ꢀ18 ꢁC. Crystal data and refine-
ment parameters for complex 1 are summarized in Table 1.
Intensity data for complex 1 were collected on a Rigaku R-
AXIS RAPID image plate diffractometer (k(Mo Ka radia-
2.3.1. [N,N-bis(2,4,6-trimethylbenzene)-1,4-
diazabutadiene] (2,4,6-Me3G)
To a 500 ml round-bottom flask equipped with a mag-
netic stir bar was added 250 ml of ethanol and (15.115 g,
111.8 mmol) of 2,4,6-Me3PhNH2. Glyoxal (8.406 g,
40 wt% solution, 55.86 mmol) was added to the clear, faint
yellow solution, and the resulting yellow solution was stir-
red at room temperature for 14 h. The solution was filtered
and the bright yellow solid thus obtained was washed with
cold ethanol and dried in vacuo. IR (KBr, cmꢀ1): tmax
1617, 1479 (sym, asym C@N). 1H NMR (500 MHz,
CDCl3): 2.21 (s, 12H, 2,6-(CH3)2); 2.34 (s, 6H, 4-(CH3));
6.94 (s, 4H, aromatic hydrogens); 8.15 (s, 2H, iminic hydro-
gens). 13C{1H} NMR (500 MHz, CDCl3): 18.68; 21.23;
127.00; 129.42; 134.72; 147.85; 163.94 (13C@N). UV–Vis:
˚
tion) = 0.71070 A) at 295 2 K. Several scans in the / and
x directions were made to increase the number of redun-
dant reflections, which were averaged over the refinement
cycles. An empirical (multi-scan) absorption correction
was applied (ABSCOR) [12]. The structure was solved by
the direct method (SIR92) [13] and refined by full-matrix
least-squares (SHELXL-97) [14]. All calculations were carried
out using the WINGX package of the crystallographic pro-
grams [15]. The benzene rings were restrained to be flat
within a standard deviation of 0.1 A (FLAT 0.10 instruc-
k
max, e (nm, Mꢀ1 cmꢀ1): 248 (12444); 370 (4445).
˚

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R. Kia et al. / Polyhedron 26 (2007) 2906–2910
R1
R
N
R
N
R1
R1
R3
R
N
R
N
R1
R3
2.3.2. [N,N-bis(2,4-dimethylbenzene)-2,3-dimethyl-1,4-
diazabutadiene] (2,4-Me2D)
1) Re(CO)5Cl, CH2Cl2/ethanol
2) AgOCOCF3/ THF
R2
R2
R2
R2
CO
Re
This ligand was prepared by a procedure similar to
2,4,6-Me3G using (14.4 g, 118.8 mmol) of 2,4-Me2PhNH2
and (4.80 g, 55.80 mmol) of diacetyl. The bright yellow
solid was washed with cold ethanol and dried in vacuo.
R3
R3
2,4,6-Me3G: R=H, R1=R2=R3= CH3
2,4-Me2D: R=CH3, R1=R2= CH3, R3= H
CO
OCOCF3
OC
[Re(CO)3(2,4,6-Me3G)(OCOCF3)] (1)
[Re(CO)3(2,4-Me2D)(OCOCF3)] (2)
IR (KBr, cmꢀ1): tmax 1633, 1488 (sym, asym C@N). H
1
Scheme 1.
NMR (500 MHz, CDCl3): 2.14 (s, 6H, 2-(CH3)); 2.17 (s,
6H, 2-(CH3)); 2.37 (s, 6H, iminic methyls); 6.58–6.60 (d,
2H, aromatic hydrogens); 7.04–7.05 (d, 2H, aromatic
hydrogens); 7.09 (s, 2H, aromatic hydrogens). UV–Vis:
equivalent of AgOCOCF3 in a mixture of ethanol and
THF in the dark. After cooling, the AgCl that formed dur-
ing the reaction was removed by filtration. The partial
removal of the solvent and addition of n-hexane resulted
in the formation of the corresponding complexes 1 and 2
in good yield. These new complexes are stable in the solid
state and in solution at room temperature and they were
characterized by the usual spectroscopic techniques. The
IR spectra of the free ligands exhibit the characteristic bands
of the symmetrical and asymmetrical stretching of the imine
group at 1617 and 1479 cmꢀ1 for 2,4,6-Me3G and 1633 and
1488 cmꢀ1 for 2,4-Me2D. The IR spectra of complexes exhi-
bit the characteristic bands in the carbonyl stretching region
as a sharp intense band at 2031 and 2023 cmꢀ1 for com-
plexes 1 and 2, respectively, and two lower-energy bands clo-
sely spaced at 1936 and 1921 cmꢀ1 for complex 1 and
1929 cmꢀ1 for complex 2, typical of Re(I) a-diimine tricar-
bonyl complexes [16,17]. The nature of the axial ligand in
the [Re(CO)3(NN)(X)] complexes influences, to some extent,
the position and the shape of the absorption band in the IR
spectra. The p-donor character of the oxygen atom in the
trifluoroacetate group increases the Re ! CO back-bond-
ing, which decreases the energy of t(CO) [18]. The NMR
spectra and peak assignments of the ligands and their com-
plexes are presented in Section 2. For complexes 1 and 2, the
signal due to the methyl groups in the ortho and para posi-
tions of the phenyl ring appears at about 2.24–2.38 and
2.07–2.40 ppm, respectively. The signal due to the iminic
methyl in complex 2 appears at about 2.36 ppm. For com-
plex 1, the signal due to the iminic hydrogen appears at
about 8.79 ppm. The signal due to the aromatic hydrogens
appears at about 7.03 and 7.30 ppm for complex 1 and at
about 6.72–7.25 ppm for complex 2. All the signals due to
the different hydrogens in the 1H NMR spectra of complexes
1 and 2 are shifted to the low-field region with respect to the
free ligands as a result of ligand coordination. The UV–Vis
spectral data of the ligands and their complexes are pre-
sented in Table 2. The UV–Vis bands of the ligands are
assigned to ligand-centered p ! p* and n ! p* transitions
[11]. The absorption spectra of the complexes can be inter-
preted by comparison with other Re(I) complexes with
ligands structurally related to those used in this work [19–
21]. The higher energy bands observed in the spectra have
been considered as intraligand p ! p* transitions, and these
are also present for the free ligands in the same spectral
regions. The longer wavelength absorption bands show a
maximum in the range 400–500 nm. These bands have been
assigned partly to metal-to-ligand charge-transfer (MLCT)
k
max, e (nm, Mꢀ1 cmꢀ1): 243 (11360); 345 (3973).
2.3.3. [Re(CO)3(2,4,6-Me3G)(OCOCF3)] (1)
A mixture of Re(CO)5Cl (0.5 mmol, 111 mg) and 2,4,6-
Me3G (0.5 mmol, 146 mg) in 20 ml CH2Cl2 and 30 ml of
absolute ethanol was heated at reflux for 3 h to give a
red-brown solution. The solution was concentrated to half
volume and a solution of AgOCOCF3 (0.5 mmol, 110 mg)
in THF was added. The mixture was refluxed for 4 h in the
dark. After cooling, the AgCl precipitate was removed by
filtration and the crude material was recrystallized from
CH2Cl2/hexane to give the carboxylate complex 1 as pure
dark-red crystals.
Anal. Calc. for C24H24F3N2O5Re: C, 44.44; H, 3.58; N,
4.15. Found; C, 44.45; H, 3.56; N, 4.20%. IR (KBr, cmꢀ1):
1
tmax 2031, 1931, 1921 (CO). H NMR (500 MHz, CDCl3):
2.24 (s, 6H, CH3); 2.29 (s, 6H, CH3); 2.38 (s, 6H, CH3);
7.03 (s, 4H, aromatic hydrogens); 8.79 (s, 2H, iminic hydro-
gens). UV–Vis: kmax, e (nm, Mꢀ1 cmꢀ1): 239 (13720); 480
(8773).
2.3.4. [Re(CO)3(2,4-Me2D)(OCOCF3)] (2)
This complex was prepared by a procedure similar to
1using 146 mg (0.5 mmol) of 2,4-Me2D. The crude material
was recrystallized from CH2Cl2/hexane to give
[Re(CO)3(2,4-Me2D)(OCOCF3)] as pure dark-red crystals.
Anal. Calc. for C25H24F3N2O5Re: C, 44.44; H, 3.58; N,
4.15. Found; C, 44.46; H, 3.60; N, 4.15%. IR (KBr,
cmꢀ1): tmax 2023, 1929 (CO). 1H NMR (500 MHz, CDCl3):
2.07–2.40 (s, 18H, 6CH3); 6.7–7.2 (6H, aromatic hydro-
gens). 13C{1H} NMR (500 MHz, CDCl3): 16.76, 17.25,
17.53, 20.16–20.18, 20.30, 20.90–20.94, 119.95–120.04,
120.55, 126.06, 126.62, 127.76, 127.96, 128.35–128.40,
131.90, 131.97, 132.26, 137.61–137.66, 145.73–145.78,
146.12, 176.59–176.80, 195.48. UV–Vis: kmax, e (nm,
M
ꢀ1 cmꢀ1): 239 (14386); 430 (9573).
3. Results and discussion
3.1. General characterization
The new fac-[Re(CO)3(DAB)(OCOCF3)] (DAB = substi-
tuted aromatic diazabutadiene ligands) complexes were
obtained via substitution reactions, as outlined in Scheme
1. The trifluoroacetateo complexes were synthesized by
allowing the in situ reaction of the halide carbonyl with 1

R. Kia et al. / Polyhedron 26 (2007) 2906–2910
2909
Table 2
UV–Vis spectral data of the DAB ligands, and complexes 1 and 2
Compound Concentration
(M)
Solvent UV–Vis kmax (nm) [e]
(Mꢀ1 cmꢀ1
)
2,4,6Me3G 9 · 10ꢀ5
CH2Cl2 248 [12444], 370 [4445]
CH2Cl2 243 [11360], 345 [3973]
CH2Cl2 239 [13720], 480 [8773]
CH2Cl2 239 [14386], 430 [9573]
2,4Me2D
1.5 · 10ꢀ3
Complex 1 7.5 · 10ꢀ5
Complex 2 7.5 · 10ꢀ5
1.40E-05
1.20E-05
1.00E-05
8.00E-06
a
Fig. 2. ORTEP drawing for complex 1. Non-hydrogen atoms are shown
as 30% probability ellipsoids.
b
i
6.00E-06
4.00E-06
Table 3
2.00E-06
˚
Selected bond distances (A) and angles (ꢁ) for complex 1
0.00E+00
-2.00E-06 1
-4.00E-06
Complex 1
1.2
1.4
1.6
1.8
Re(1)–N(1)
Re(1)–N(2)
Re(1)–O(4)
Re(1)–C(1)
Re(1)–C(2)
Re(1)–C(3)
2.186(4)
2.160(4)
2.153(3)
1.896(6)
1.909(6)
1.923(5)
C(1)–Re(1)–O(4)
C(2)–Re(1)–C(3)
C(3)–Re(1)–N(1)
N(1)–Re(1)–N(2)
N(2)–Re(1)–C(2)
179.7(2)
88.3(2)
99.4(2)
74.1(2)
98.3(2)
E
(a) Complex (1) and (b) Complex (2)
Fig. 1. Cyclic voltammograms of 1 (a) and 2 (b) in CH2Cl2 at 293 K (scan
rate, 100 mV/s, C = 2.5 · 10ꢀ4 M).
Table 4
transitions, mixed with a p ! p* transition of the Re(DAB)
chelate. The electrochemical behaviour of complexes 1 and 2
was examined by means of cyclic voltammetry (CV) in
CH2Cl2 (Fig. 1). Anodic scans reveal a single reversible oxi-
dation at 1.44 and 1.66 V versus Ag/AgCl for the complexes
1 and 2, respectively. This is assigned to the Re(II)/Re(I)
redox couple, which is similar to the anodic peak potential
reported for similar systems [22]. Complexes 1 and 2 show
quasireversible redox couples with E1/2 values of 1.36 and
1.59 V, respectively. The cyclic voltammetry peak-to-peak
separations (DEp) of 160 and 130 mV were observed at a
scan rate (t) of 100 mVꢀ1 for complexes 1 and 2,
respectively.
Parameters of hydrogen bonding interactions in complex 1
Complex 1
D–Hꢂ ꢂ ꢂA
Hꢂ ꢂ ꢂA
Dꢂ ꢂ ꢂA
D–Hꢂ ꢂ ꢂA
(ꢁ)
˚
˚
(A)
(A)
C(151)–
2.44
3.308(8)
150
H(15B)ꢂ ꢂ ꢂO(4)
C(6)–H(6)ꢂ ꢂ ꢂO(5)i
C(131)–
H(13A)ꢂ ꢂ ꢂF(1)ii
2.13
2.48
2.940(8)
3.399(10) 159
145
Symmetry codes: (i) 1 + x, y, z; (ii) 1 ꢀ x, ꢀ1/2 + y, 1/2 ꢀ z.
N(1)–Re(1)–N(2) bite angle is 74.1(2)ꢁ and Re–N (N1,
N2) bond lengths are 2.186(4) and 2.160(4) A, respec-
˚
tively. Owing to the steric requirements of the N,N0-biden-
tate chelating 2,4,6-Me3G ligand the equatorial bond
angles range from 74.1(2)ꢁ to 99.4(2)ꢁ. The axial C(1)–
Re(1)–O(4) bond angle is 179.7(2)ꢁ. Due to the p-donor
character of the trifluoroacetate ligand, the axial Re–C
3.2. X-ray structure of [Re(CO)3(2,4,6-
Me3G)(OCOCF3)] (1)
The molecular structure of 1 is shown in Fig. 2, selected
bond lengths and angles are listed in Table 3. The Re
atom has a distorted octahedral configuration and is coor-
dinated by two carbonyl groups and the diimine group of
the 2,4,6-Me3G ligand in the equatorial plane. Octahedral
coordination is completed at the axial positions by
another carbonyl ligand and a carboxyl O atom of the tri-
fluoroacetate anion. The equatorial Re–C distances are
˚
bond length of 1.896(6) A is slightly shorter than the
corresponding equatorial Re–C distances. The CF3 group
has high thermal motion consistent with some unresolved
rotational disorder, as is often found in other trifluoroac-
etate compounds [9,23,24]. The overall structural similar-
ity of 1 with the previously reported [Re(CO)3(2,4-Me2D)
(OCOCF3)] complex [9] reflects the strong tendency of
substituted diazabutadiene ligands to enforce a dis-
torted-octahedral geometry at Re. In addition, there are
weak intra- and intermolecular C–Hꢂ ꢂ ꢂO, as well as inter-
molecular C–Hꢂ ꢂ ꢂF interactions (Table 4) in the crystal
lattice of 1.
˚
1.909(6) and 1.923(5) A, respectively. The equatorially
disposed N,N0-bidentate chelating 2,4,6-Me3G ligand
forms a ReN2C2 five-membered chelate ring and the mean
deviation of these atoms from the least-square plane is
˚
only 0.0274 A. In this five-membered chelate ring the

2910
R. Kia et al. / Polyhedron 26 (2007) 2906–2910
[2] A.J. Lees, Chem. Rev. 87 (1987) 711.
4. Conclusion
[3] A.I. Baba, J.R. Shaw, J.A. Simon, R.P. Thummel, R.H. Schmehl,
Coord. Chem. Rev. 171 (1988) 43.
[4] D.J. Stufkens, A. Vlcek, Coord. Chem. Rev. 171 (1988) 127.
[5] D.J. Stufkens, Comments Inorg. Chem. 13 (1992) 359.
[6] (a) J. Hawecker, J.M. Lehn, R. Ziessel, J. Chem. Soc., Chem.
Commun (1983) 536;
The fac-[Re(CO)3(DAB)(OCOCF3)] (DAB = 2,4,6-
Me3G, 2,4Me2D) rhenium(I) complexes have been pre-
pared and characterized by IR, UV–Vis, NMR,
electrochemical and X-ray diffraction techniques. Varia-
tions in the electronic properties related to rhenium(I),
the carbonyl and X ligands, such as electronic transitions,
CO stretching and some crystallographic parameters of
the complexes, were interpreted on the basis of the DAB
and X ligands. It is clear from the data that, by varying
the nature of the DAB ligands attached to rhenium, the
electronic properties of the fac-[Re(CO)3(DAB)(OCOCF3)]
complexes could be tuned.
(b) B.P. Sullivan, T.J. Meyer, J. Chem. Soc., Chem. Commun. (1984)
1244;
(c) G. Calzaferri, K. Hadener, J. Li, J. Photochem. Photobiol. A 64
(1992) 259.
[7] C. Kutal, A.J. Corbin, G. Ferraudi, Organometallics 6 (1987)
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[8] B.P. Sullivan, T.J. Meyer, J. Chem. Soc., Chem. Commun. (1984)
1414, and references therein.
´
´
´
[9] R. Kia, V. Mirkhani, A. Deak, A. Kalman, Acta Crystallogr., Sect. E
61 (2005) m566.
[10] D.D. Perrin, W.L. Armarego, D.R. Perrin, Purification of Laboratory
Chemicals, second ed., Pergamon, New York, 1990.
[11] H. tom Dieck, I.W. Renk, Chem. Ber. 104 (1971) 92.
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Acknowledgements
R.K. and V.M. thank the University of Isfahan for par-
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Appendix A. Supplementary material
CCDC 630420 contains the supplementary crystallo-
graphic data for 1. 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: deposit@ccdc.cam.ac.uk. Supplemen-
tary data associated with this article can be found, in the
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