Oxidorhenium(V) complexes with phenolate- and carboxylate-based ligands: Structure and catalytic epoxidation

Article abstract of DOI:10.1002/ejic.201200277

Several oxidorhenium(V) complexes with phenolate- and carboxylate-based ligands were synthesized: [ReOCl(hpbi)₂]·THF, [ReOCl(hmpbta)₂], [ReOBr(hmpbta)₂], [ReOCl(hpbo) ₂], [ReOCl(hpbt)₂]·2MeCN, [ReO(OMe)(quin) ₂], [ReO(OMe)(pic)₂], [ReO(OMe)(2,5-dipic) ₂]·C₅H₅N, [ReOCl(pic)₂], and [ReOCl(3-ind)₂] [in which Hhpbi = 2-(2-hydroxyphenyl)-1H- benzimidazole, Hhmpbta = 2-(2-hydroxy-5-methylphenyl)benzotriazole, Hhpbo = 2-(2-hydroxyphenyl)-2-benzoxazole, Hhpbt = 2-(2-hydroxyphenyl)benzothiazole, Hquin = quinaldic acid, picH = picolinic acid, 2,5-dipicH = 2,5- pyridinedicarboxylic acid, and 3-indH = indazole-3-carboxylic acid]. The compounds were characterized by spectroscopic methods and single-crystal X-ray diffraction analysis. Interestingly, the complex [ReO(OMe)(quin)₂] is a rare trans-N,N and trans-O,O isomer of [ReOX(N-O)₂] with two chelating quinoline-2-carboxylate ligands in the equatorial plane and a linear axial [O=Re-OMe] unit. The other disubstituted compounds were found to be the most common cis-N,N structure of [ReOX(N-O)₂] with the oxygen atom of one of the chelating ligands in a trans position to the oxido ligand. All the complexes were tested in the epoxidation of cyclooctene with tert-butyl hydroperoxide (3 equiv.). The lowest conversion of only 3 % has been confirmed for [ReOCl(hpbi)₂]. All other complexes reached yields of cyclooctane oxide between 58 and 75 %. Several oxidorhenium(V) complexes that contain phenolate- and carboxylate-based ligands were synthesized and characterized by spectroscopic means and by X-ray crystal structure analysis. The complexes are air- and moisture-stable and show catalytic activity for the epoxidation of cyclooctene. Copyright

Full text of DOI:10.1002/ejic.201200277

Job/Unit: I20277
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Date: 28-06-12 18:07:48
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FULL PAPER
DOI: 10.1002/ejic.201200277
Oxidorhenium(V) Complexes with Phenolate- and Carboxylate-Based Ligands:
Structure and Catalytic Epoxidation
Barbara Machura,*[a] Mariusz Wolff,[a] Dominik Tabak,[b] Jörg A. Schachner,[c] and
Nadia C. Mösch-Zanetti[c]
Keywords: Rhenium / Phenolate ligands / Carboxylate ligands / Epoxidation
Several oxidorhenium(V) complexes with phenolate- and
carboxylate-based ligands were synthesized: [ReOCl(hpbi)2]·
THF, [ReOCl(hmpbta)2], [ReOBr(hmpbta)2], [ReOCl(hpbo)2],
[ReOCl(hpbt)2]·2MeCN, [ReO(OMe)(quin)2], [ReO(OMe)-
(pic)2], [ReO(OMe)(2,5-dipic)2]·C5H5N, [ReOCl(pic)2], and
[ReOCl(3-ind)2] [in which Hhpbi = 2-(2-hydroxyphenyl)-1H-
benzimidazole, Hhmpbta = 2-(2-hydroxy-5-methylphenyl)-
benzotriazole, Hhpbo = 2-(2-hydroxyphenyl)-2-benzoxazole,
Hhpbt = 2-(2-hydroxyphenyl)benzothiazole, Hquin = quin-
aldic acid, picH = picolinic acid, 2,5-dipicH = 2,5-pyridined-
icarboxylic acid, and 3-indH = indazole-3-carboxylic acid].
The compounds were characterized by spectroscopic meth-
ods and single-crystal X-ray diffraction analysis. Interest-
ingly, the complex [ReO(OMe)(quin)2] is a rare trans-N,N
and trans-O,O isomer of [ReOX(N–O)2] with two chelating
quinoline-2-carboxylate ligands in the equatorial plane and
a linear axial [O=Re–OMe] unit. The other disubstituted com-
pounds were found to be the most common cis-N,N structure
of [ReOX(N-O)2] with the oxygen atom of one of the chelat-
ing ligands in a trans position to the oxido ligand. All the
complexes were tested in the epoxidation of cyclooctene with
tert-butyl hydroperoxide (3 equiv.). The lowest conversion of
only 3% has been confirmed for [ReOCl(hpbi)2]. All other
complexes reached yields of cyclooctane oxide between 58
and 75%.
bility towards hydrolysis make them attractive options as
catalysts. For this reason, some effort has been recently de-
voted to the investigation of ReV complexes as catalysts in
epoxidation reactions of olefins. Detailed studies have been
performed for monosubstituded or disubstituted complexes
of the type [ReOX2L(PPh3)] and [ReOXL2] with β-ketimin-
ate ligands, pyrazole phenolate and naphtholate ligands,
acetylacetone-derived Schiff bases, and oxazolinylmethox-
ido ligands, as well as for [ReOX2L] and [ReOXL] with tri-
dentate or tetradentate Schiff bases or pyridazine phenolate
ligands. However, only limited success has been attained as
the reported ReV complexes showed lower activity or pro-
ductivity than rhenium(VII) systems.[8–16] Therefore, there
is a need for further investigations on furnishing novel rhe-
nium(V) complexes with ligands that exhibit higher stability
towards oxidation.
However, oxidorhenium(V) complexes were found to be
highly successful in OAT reactions. Espenson and co-
workers reported some rhenium(V) complexes to be ef-
ficient catalysts of oxygen-atom transfer from pyridine N-
oxide to phosphanes.[17,18] Abu-Omar and co-workers de-
veloped a new class of molecular rhenium(V) oxotransfer-
ases that incorporate oxazoline-derivatized phenolates,
which efficiently catalyze the reduction of perchlorate to
chloride ions, one of the most challenging reactions due to
its kinetic hindrance and environmental importance.[19–21]
The recent success of the rhenium(V) complexes and the
need for novel catalytically active species prompted us to
Introduction
The widespread contemporary interest in the coordina-
tion chemistry of rhenium arises mainly from the introduc-
tion of β–-emitting isotopes 188Re and 186Re in radiotherapy
and its similarity with technetium, the metastable γ-emit-
ting isotope 99mTc, which plays an important role in diag-
nostic nuclear medicine. Thus, there is still a need for basic
knowledge about the structural and spectroscopic proper-
ties, redox activities, and mechanism of ligand-substitution
reactions to develop new and improved Re radiopharma-
ceuticals.[1–4]
Another area of growing interest for rhenium–oxido
compounds is their application as catalysts, particularly in
oxidation and oxygen-atom-transfer (OAT) reactions. This
field is clearly highlighted by methyltrioxidorhenium(VII),
one of the most versatile and highly efficient transition-
metal catalysts known to date.[5–7]
Oxidorhenium(V) compounds have been far less ex-
plored, although straightforward preparation and high sta-
[a] Department of Crystallography, Institute of Chemistry,
University of Silesia,
9th Szkolna St., 40-006 Katowice, Poland
E-mail: basia@ich.us.edu.pl
[b] Department of Organic Chemistry, Institute of Chemistry,
University of Silesia,
9th Szkolna St., 40-006 Katowice, Poland
[c] Institute of Chemistry, Karl-Franzens-University Graz,
Stremayrgasse 16, 8010 Graz, Austria
E-mail: nadia.moesch@uni-graz.at
Eur. J. Inorg. Chem. 0000, 0–0
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B. Machura et al.
FULL PAPER
synthesize a set of oxo compounds of the general formula rings and O-donor groups allows us to expect unusual elec-
[ReOX(N–O)2] and investigate their potential as catalysts tronic influences on the coordinating capability as well as
in oxidation reactions. Depending on the type of chelating on the catalytic activity.
ligand, compounds investigated herein can be divided into
two groups: those that incorporate ligands structurally re-
lated to oxazoline-derivatized phenolates investigated by
Results and Discussion
Abu-Omar et al.,[19–21] namely, 2-(2-hydroxyphenyl)-1H-
benzimidazole (Hhpbi), 2-(2-hydroxy-5-methylphenyl)benzo-
triazole (Hhmpbta), 2-(2-hydroxyphenyl)-2-benzoxazole
Synthesis
Phenolate-disubstituted oxidorhenium(V) complexes
[ReOCl(N–O)2] (1–4) were obtained by treatment of
[ReOCl3(OPPh3)(SMe2)] with the corresponding ligand
(2 equiv.) 2-(2-hydroxyphenyl)-1H-benzimidazole (Hhpbi),
2-(2-hydroxy-5-methylphenyl)benzotriazole (Hhmpbta), 2-
(2-hydroxyphenyl)-2-benzoxazole (Hhpbo), and 2-(2-hy-
droxyphenyl)benzothiazole (Hhpbt) (Scheme 2).
To investigate the effect of the halide ion, the reaction of
[ReOBr3(OPPh3)(SMe2)] with 2-(2-hydroxy-5-methylphen-
yl)benzotriazole was also examined and [ReOBr(hmpbta)2]
(5) was isolated.
(Hhpbo), and 2-(2-hydroxyphenyl)benzothiazole (Hhpbt),
and those that include bidentate ligands based on an aro-
matic heterocycle and a carboxylic acid as second and
charge-neutralizing coordinating functionality [quinaldic
acid (quinH), picolinic acid (picH), 2,5-pyridinedicarbox-
ylic acid (2,5-dipicH), and indazole-3-carboxylic acid (3-
indH)]. Phenolate- and carboxylate-based ligands employed
in this study are shown in Scheme 1. The use of various
chelating ligands that incorporate different heterocycle
As expected, the metal precursors [ReOX3(OPPh3)-
(SMe2)] turned out to be an excellent starting material for
preparation of these complexes. The yields obtained were
comparable with those reported for alternative metal
precursor [NBu4][ReOX4][22] and significantly higher than
[ReOX3(PPh3)2], which gave only minor amounts of
[ReOX2(N–O)2].[23] Complexes 1–5 show high stability to-
ward air and moisture both in the solid state and in solution
for several months at ambient temperature. They exhibit
moderate solubility in strong polar solvents such as thf,
acetonitrile, acetone, chloroform, methanol, and ethanol,
and are insoluble in medium polar and apolar solvents.
1
The H NMR spectra of these complexes confirmed the
occurrence of only one isomer in solution, which was shown
to contain nonequivalent N–O ligands. Particularly charac-
teristic are protons of the N–H group of the imidazole ring
in 1 and methyl groups attached to the phenolate ring in 2
and 5, which gave nonequivalent chemical shifts (δ = 13.80
and 13.64 ppm for 1, δ = 2.58 and 2.05 ppm for 2, and δ =
2.58 and 2.04 ppm for 5).
Scheme 1. (a) Phenolate- and (b) carboxylate-based ligands em-
ployed in this study.
Scheme 2.
2
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Oxidorhenium(V) Complexes
The IR spectra were characterized by strong absorptions
at approximately 960 cm–1 that were assigned to the Re=O
stretching frequencies. This value is in the range typical of
neutral six-coordinate mono-oxidorhenium(V) complexes
with an anionic phenolate oxygen coordinated trans to the
oxo group.[13,14,24] The absorptions in the region 1630–
1520 cm–1 were assigned to the ν(C=N) modes of the che-
lating ligands.
To synthesize carboxylate-disubstituted oxidorheni-
um(V) complexes, two metal precursors [ReOCl3(OPPh3)-
(SMe2)] and [ReO2(py)4]Cl were used. The better results
were achieved in the case of synthetic strategy based on
the reaction of [ReO2(py)4]Cl with carboxylic acids, which
yielded the compounds [ReO(OMe)(N–O)2] (6–8;
Scheme 3).
Scheme 4.
All carboxylate–rhenium(V)–oxido complexes 6–10 show
high stability toward air and moisture both in the solid state
and in solution, but compounds 7, 8, and 10 exhibit limited
solubility in most common solvents, which prevented the
recording of their 13C NMR spectra.
1
The H NMR spectrum of 6 revealed only one set of
ligand resonances, thus indicating a higher symmetric spe-
cies in contrast to complexes 7–10 with two sets of signals
1
in the H NMR spectra for the attached ligands.
In principle, there are several different possible orienta-
tions for the ligands in complexes of general formula [Re-
OX(N–O)2], as shown in Scheme 5.
Scheme 3.
Apart from its high yield, this procedure has another im-
portant advantage: the desired complexes precipitate di-
rectly from the reaction mixture under prolonged reflux
conditions and are easily isolated by simple filtration. Treat-
ment of the alternative metal precursor [ReOCl3(OPPh3)-
(SMe2)] with the corresponding carboxylic acid (2 equiv.) in
MeOH heated at reflux led to the disubstituted complexes
[ReOCl(N–O)2] (9, 10; Scheme 4), but the yields obtained
were lower than [ReO2(py)4]Cl.
Most interestingly, the choice of metal precursor turned
out to be crucial in the synthesis of the carboxylate-disub-
stituted rhenium(V) complexes. Attempts to synthesize the
disubstituted rhenium complex of indazole-3-carboxylate li-
gand by employing [ReO2(py)4]Cl failed. They yielded an
insoluble pink powder, which prevented its further charac-
terization. The desired complex [ReOCl(3-ind)2] (10) was
obtained by using [ReOCl3(OPPh3)(SMe2)].
Scheme 5. Possible ligand orientations for [ReOX(N–O)2] com-
plexes.
Generally, they can be divided into two subgroups: (i)
with the X ligand coordinated trans to the Re=O group
In contrast, treatment of [ReO2(py)4]Cl with 2,5-pyr- (types A and B), and (ii) with the X ligand cis to the Re=O
azinedicarboxylic acid led to [ReO(OMe)(2,5-dipic)2], moiety (types C–F). Moreover, five of the possible consti-
whereas a synthetic procedure with [ReOCl3(OPPh3)- tution isomers (types B–F) exist as a pair of enantiomers.
(SMe2)] resulted in the formation of an unidentified reac-
Unambiguous determination of the ligand arrangement
1
tion mixture as revealed by H NMR spectroscopy. Pyr- around the metal center in 6–10 was possible by single-crys-
idine-2-carboxylic and quinoline-2-carboxylic acids reacted tal X-ray diffraction, and structural studies are in good
with both metal precursors to give disubstituted ReV–oxido agreement with the NMR spectroscopic results. Complexes
complexes [ReO(OMe)(N–O)2] or [ReOCl(N–O)2].
7–10 adopt the most common structure of type D and dis-
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1
play two sets of H NMR spectroscopic signals for the at-
tached ligands, which is in accordance with their nonequiv-
alent coordination geometry. The ligands of 6 are arranged
around the Re center as in isomer A, and two equivalent
N–O ligands revealed only one set of ligand resonances in
the NMR spectra.
For each carboxylato-rhenium(V) complex, IR spec-
troscopy confirmed the presence of an Re=O fragment. The
strong Re=O stretching mode was found at 955 cm–1 for 6
and approximately 985 cm–1 for 7–10. The bathochromic
shift of this vibration in complex 6, which incorporates a
trans-[ReO(OMe)]2+ unit, is normal and results from the
competition of the methoxide group for π bonding with the
dπ orbitals of the metal, thereby leading to the weakness of
the Re=O bond.[25] A higher wavenumber of 7–10 indicates
that the Re–carboxylate bond trans to the oxido ligand is
not very strong and does not compete effectively for the dRe
orbitals. Coordination of the carboxylate group was con-
firmed by absorptions in the regions 1730–1660 and 1330–
1280 cm–1, which are assigned to the asymmetric and sym-
metric stretching vibration of the COO– group, respectively.
Figure 2. Molecular views of carboxylate disubstituted compounds
[ReO(OMe)(N–O)2] with selected atom numbering.
Molecular Structures of the Complexes [ReOX(N–O)2]
The molecular structures of compounds 1 and 3–10 were
determined by single-crystal X-ray diffraction analysis. The
perspective molecular views of the complexes are shown in
Figures 1, 2, and 3. Crystallographic data are presented in
Tables 1 and 2, and selected bond lengths and angles are
given in Tables 3, 4, and 5. The molecular structure of 2
was discussed in our previous paper.[23]
Figure 3. Molecular views of carboxylate disubstituted compounds
[ReOCl(N–O)2] with selected atom numbering.
carboxylate ligands are situated in an equatorial plane with
a trans-N,N trans-O,O arrangement, and the coordination
site trans to the oxido ligand is occupied by the methoxy
group. Such ligand arrangement around the central ion
makes complex 6 a very rare example of [ReOX(N–O)2]
complexes.
A related [ReOCl(N–O)2] compound with two symmetri-
cally coordinated salen ligands in the equatorial plane and
a linear [O=Re–X] moiety was isolated by Herrmann and
co-workers in 2007 as a side product in the reaction of
[NBu4][ReOCl4] with the bis(alkyl/aryl)-2-pyridylalcoholate
ligand.[8] A trans O=Re–X conformation has also been con-
firmed in a few other [ReOXL2] compounds, namely,
[ReOCl(o-C6O2Cl4)(Ph2PCH2CH2PPh2)],[25] [ReOCl(NH2-
CH2CH2S)2],[26] [ReOCl{NH(o-C6H4)SCH3}2],[27] and
[ReOCl(OPhsal){P(CH3)2Ph}] [OPhsal = N-(2-oxidophen-
yl)salicylideneiminate].[28]
Complexes 1–5 and 7–10 were found to be the cis-N,N
isomer of type D (Scheme 1). The equatorial plane of these
compounds consists of the two nitrogen atoms, an oxygen
atom from the chelating ligand, and the halide atom or
methoxy group. The oxido ligand along the axial direction
Figure 1. Molecular views of phenolate disubstituted compounds
[ReOCl(N–O)2] with selected atom numbering.
All examined complexes show a six-coordinate rhenium is trans to the phenol or carboxylic oxygen atom. This is
atom with distorted octahedral geometries. Each phenolate due to a strong trans influence of the oxido group, which
or carboxylate ligand chelates to the oxidorhenium core forces the harder oxygen atom of the N–O ligand into a
through N and O atoms. In complex 6, two quinoline-2- trans position. Such stereochemistry is well documented in
4
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Oxidorhenium(V) Complexes
Table 1. Crystal data and structure refinement for complexes 1, 3, 4, and 5.
1
3
4
5
Empirical formula
Formula weight
C30H26ClN4O4Re
728.20
C26H16ClN2O5Re
658.06
C30H22ClN4O3S2Re
772.29
C26H20BrN6O3Re
730.59
T [K]
Crystal system
Space group
293.0(2)
monoclinic
P21/n
293.0(2)
monoclinic
P21/n
293.0(2)
monoclinic
P21/n
293.0(2)
orthorhombic
Pbca
a [Å]
b [Å]
c [Å]
α [°]
12.9021(10)
13.6136(8)
15.9407(16)
90
9.2556(13)
14.5250(3)
17.5280(2)
90
13.3205(4)
15.9693(5)
13.4978(4)
90
15.8338(6)
15.8517(8)
19.9989(9)
90
β [°]
110.716(10)
90
2618.9(4)
4
1.847
4.788
104.320(12)
90
2283.2(3)
4
1.914
5.482
94.374(3)
90
2862.88(15)
4
1.792
4.524
90
90
5019.6(4)
8
1.934
γ [°]
V [Å3]
Z
ρcalcd. [gcm–3]
μ [mm–1]
6.475
F(000)
1432
1272
1512
2816
Crystal size [mm]
θ range for data collection [°]
Reflections collected
Independent reflections
Completeness to 2θ = 25° [%]
Min. and max. transmission
Data / restraints / parameters
Goodness-of-fit on F2
Final R indices [IϾ2σ(I)]
0.851ϫ0.203ϫ0.011
3.38 to 25.00
23034
4568 (Rint = 0.0652)
99.1
0.511 to 1.000
4568 / 0 / 361
1.138
R1 = 0.0343
wR2 = 0.1083
R1 = 0.0498
wR2 = 0.1507
1.568 and –1.650
0.158ϫ0.054ϫ0.028 1.318ϫ0.504ϫ0.424
3.61 to 25.00
9935
3997 (Rint = 0.0593)
99.7
0.505 to 1.000
3997 / 0 / 316
1.010
R1 = 0.0541
wR2 = 0.1313
R1 = 0.0738
wR2 = 0.1422
3.835 and –1.976
0.346ϫ0.092ϫ0.086
3.52 to 25.00
22712
4403 (Rint = 0.0437)
99.7
0.475 to 1.000
4403 / 0 / 336
0.975
R1 = 0.0207
wR2 = 0.0555
R1 = 0.0339
wR2 = 0.0572
0.700 and –0.539
3.72 to 25.00
14038
4980 (Rint = 0.0268)
98.8
0.362 to 1.000
4980 / 0 / 372
0.952
R1 = 0.0221
wR2 = 0.0505
R1 = 0.0331
wR2 = 0.0521
0.744 and –0.809
R indices (all data)
Largest diff. peak / hole [eÅ–3]
Table 2. Crystal data and structure refinement for complexes 6, 7, 8, 9, and 10.
6
7
8
9
10
Empirical formula
Formula weight
T [K]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C21H15N2O6Re
577.55
293.0(2)
C13H11N2O6Re
477.44
293.0(2)
monoclinic
P21/c
14.3597(6)
7.5279(2)
14.3971(6)
90
113.328(5)
90
1429.08(9)
4
2.219
8.534
904
C20H16N3O10Re
644.56
293(2)
monoclinic
P21/n
13.1896(5)
7.2002(2)
22.2021(8)
90
99.129(3)
90
2081.78(12)
4
2.057
5.903
C12H8ClN2O5Re
481.85
293.0(2)
monoclinic
Cc
7.7249(3)
12.0684(5)
15.1121(6)
90
99.368(4)
90
1390.07(10)
4
2.302
8.956
904
C17H14ClN4O6Re
591.97
293.0(2)
triclinic
triclinic
¯
¯
P1
P1
7.6615(15)
7.9952(16)
17.5095(4)
83.332(4)
84.009(4)
61.519(6)
934.89(8)
2
7.2256(7)
8.6703(8)
16.4617(16)
94.924(8)
93.370(8)
110.372(9)
958.87(16)
2
γ [°]
V [Å3]
Z
ρcalcd. [gcm–3]
μ [mm–1]
F(000)
2.052
6.543
556
2.050
6.519
568
1248
Crystal size [mm]
0.099ϫ0.098ϫ0.056 0.402ϫ0.279ϫ0.031 0.218ϫ0.132ϫ0.065 0.162ϫ0.110ϫ0.108 0.145ϫ0.122ϫ0.014
θ range for data collection [°] 3.41 to 25.00
3.39 to 25.00
25290
3.38 to 25.00
14891
3.38 to 25.00
10106
3.73 to 25.00
17532
Reflections collected
17400
Independent reflections
Completeness to 2θ = 25° [%] 99.7
3279 (Rint = 0.0582)
2502 (Rint = 0.0878)
99.7
3668 (Rint = 0.0353)
99.8
2438 (Rint = 0.0359)
99.8
3374 (Rint = 0.0552)
99.6
Min. and max. transmission
Data / restraints / parameters 3279 / 0 / 266
Goodness-of-fit on F2
0.462 to 1.000
0.108 to 1.000
2502 / 0 / 200
1.100
0.545 to 1.000
3668 / 0 / 308
1.313
0.481 to 1.000
2438 / 2 / 190
1.027
0.397 to 1.000
3374 / 0 / 264
1.057
1.094
Final R indices [IϾ2σ(I)]
R1 = 0.0225
wR2 = 0.0525
R1 = 0.0261
wR2 = 0.0537
R1 = 0.0334
wR2 = 0.0881
R1 = 0.0397
wR2 = 0.0918
0.916 and –1.295
R1 = 0.0342
wR2 = 0.0824
R1 = 0.0387
wR2 = 0.0836
1.129 and –0.905
R1 = 0.0201
wR2 = 0.0384
R1 = 0.0221
wR2 = 0.0390
0.624 and –0.413
R1 = 0.0329
wR2 = 0.0826
R1 = 0.0389
wR2 = 0.0843
2.259 and –0.794
R indices (all data)
Largest diff. peak / hole [eÅ–3] 0.548 and –1.216
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B. Machura et al.
FULL PAPER
Table 3. Selected bond lengths [Å] and angles [°] of compounds 1,
3, 4, and 5.
Table 5. Selected bond lengths [Å] and angles [°] of compounds 9
and 10.
1
3
4
5
9
10
Re1–O1
Re1–O2
Re1–O3
Re1–N1
Re1–N2
Re1–X1
O1–Re1–O2 103.0(3)
O1–Re1–O3 166.0(3)
O2–Re1–O3 86.4(2)
O1–Re1–N1 88.0(3)
O2–Re1–N1 87.8(2)
O3–Re1–N1 82.0(2)
O1–Re1–N2 92.1(3)
O2–Re1–N2 164.7(3)
O3–Re1–N2 79.0(2)
N1–Re1–N2 94.6(2)
O1–Re1–X1 101.9(2)
O2–Re1–X1 85.27(17)
O3–Re1–X1 89.04(17)
N1–Re1–X1 168.98(19)
N2–Re1–X1 89.94(19)
1.682(6)
1.982(6)
2.019(6)
2.083(6)
2.109(7)
2.359(2)
1.654(7)
1.977(6)
1.986(6)
2.111(7)
2.127(8)
2.353(3)
105.2(3)
165.6(3)
82.7(3)
85.1(3)
88.3(3)
83.0(3)
91.9(3)
162.8(3)
81.2(3)
95.5(3)
99.7(2)
1.673(2)
1.966(2)
1.984(2)
2.133(3)
1.685(3)
1.968(3)
1.976(2)
2.112(3)
Re1–O1
Re1–O4
Re1–O2
Re1–N2
Re1–N3
Re1–N1
Re1–Cl1
1.674(4)
1.986(6)
2.007(5)
2.092(5)
–
2.120(7)
2.3482(18)
109.8(2)
162.2(2)
85.6(2)
91.4(2)
79.93(19)
82.5(2)
–
1.681(4)
1.999(5)
2.059(4)
–
2.076(5)
2.107(5)
2.3711(18)
109.9(2)
159.8(2)
89.84(18)
–
2.140(3)
2.134(3)
2.3633(9)
103.69(11)
165.33(11)
85.40(10)
87.01(11)
90.25(10)
81.39(10)
91.04(11)
164.66(10)
81.07(10)
94.81(10)
100.94(9)
2.4856(5)
102.71(13)
162.33(12)
88.49(11)
86.64(13)
87.63(12)
80.14(12)
89.73(13)
167.41(12)
79.90(11)
95.12(12)
102.10(10)
87.57(9)
O1–Re1–O4
O1–Re1–O2
O4–Re1–O2
O1–Re1–N2
O4–Re1–N2
O2–Re1–N2
O1–Re1–N3
O4–Re1–N3
O2–Re1–N3
O1–Re1–N1
O4–Re1–N1
O2–Re1–N1
N2–Re1–N1
N3–Re1–N1
O1–Re1–Cl1
O4–Re1–Cl1
O2–Re1–Cl1
N2–Re1–Cl1
N3–Re1–Cl1
N1–Re1–Cl1
–
–
96.2(2)
78.53(19)
83.44(18)
86.7(2)
163.26(19)
73.42(17)
–
99.0(2)
97.42(17)
87.74(15)
87.12(13)
–
–
–
89.5(2)
160.5(2)
74.9(2)
97.8(2)
–
98.97(16)
90.21(15)
89.42(14)
167.66(15)
–
87.27(19) 85.74(8)
92.7(2)
174.2(2)
87.7(2)
91.09(7)
171.75(7)
87.32(7)
91.86(8)
170.77(8)
87.93(9)
Table 4. Selected bond lengths [Å] and angles [°] of compounds 6,
7, and 8.
163.30(14)
91.46(15)
6
7
8
89.03(18)
Re1–O2
Re1–O1
Re1–O5
Re1–O7
Re1–O3
Re1–N1
Re1–N2
O1–C1
1.696(3)
1.893(3)
2.037(3)
–
2.068(3)
2.131(3)
2.138(3)
1.388(5)
170.59(13)
99.94(14)
86.15(13)
–
1.671(5)
1.937(5)
1.995(5)
–
2.081(4)
2.121(5)
2.132(6)
1.419(9)
104.4(3)
109.7(2)
89.9(2)
–
1.683(5)
1.927(5)
–
2.006(5)
2.075(5)
2.098(6)
2.139(6)
1.409(10)
102.9(3)
–
All compounds give bond lengths for Re=O [1.654(7)–
1.996(3) Å; Tables 2, 3, and 4] within the expected range
for
six-coordinate
monooxidorhenium(V)
com-
plexes.[8,12–16,22–28] The Re=O distance of 6 [1.696(3) Å] is
slightly longer than Re=O bond lengths in 7 [1.671(5) Å]
and in 8 [1.683(5) Å]. This elongation of Re=O in 6 is ac-
companied by a small shortening of the Re–O(methoxy)
distance [1.893(3) Å in 6, 1.937(5) Å in 7, and 1.927(5) Å in
8]. It seems to be a consequence of the competition of the
methoxide with the oxido group in the interaction with the
dπ orbitals of the metal and is a typical feature of com-
O2–Re1–O1
O2–Re1–O5
O1–Re1–O5
O2–Re1–O7
O1–Re1–O7
O2–Re1–O3
O1–Re1–O3
O5–Re1–O3
O5–Re1–N1
O2–Re1–N1
O1–Re1–N1
O7–Re1–O3
O7–Re1–N1
O3–Re1–N1
O2–Re1–N2
O1–Re1–N2
O5–Re1–N2
O7–Re1–N2
O3–Re1–N2
N1–Re1–N2
C1–O1–Re1
–
108.6(3)
93.7(2)
160.9(2)
86.4(2)
–
–
–
91.38(14)
82.63(13)
168.69(12)
100.64(12)
95.86(14)
90.00(13)
–
159.0(2)
86.1(2)
88.1(2)
162.2(2)
88.1(2)
85.8(2)
–
–
plexes that incorporate a linear core [O=Re–OR]2+ [29,30]
.
89.6(3)
84.7(2)
87.1(2)
161.6(2)
74.5(2)
93.1(2)
163.8(2)
–
78.3(2)
79.1(2)
98.4(2)
123.0(6)
However, the weakening of the Re=O bond in 6 is better
illustrated by a significant bathochromic shift for ν(Re=O)
in 6 discussed above. In all reported complexes, the O=Re–
–
–
77.96(12)
90.64(13)
83.51(12)
78.52(12)
–
101.57(12)
173.49(12)
141.2(3)
74.3(2)
94.7(3)
160.1(2)
78.5(2)
–
77.5(2)
100.3(2)
122.1(5)
O
trans angles are significantly below the ideal of 180° for an
octahedral complex, and the interatomic distances between
the rhenium atom and phenolate or carboxylate oxygen
atom in a trans position to the terminal oxido ligand are
longer than the corresponding Re–O bonds in the equato-
rial plane, which seems to be a typical feature of cis-N,N
isomers of [ReOX(N–O)2] of type D.
The nitrogen atoms of 6 are coordinated in a trans posi-
the literature and seems to be the most common structure tion to each other with comparable bond lengths of
type for [ReOX(N–O)2] complexes.[12,14,22,23,29] There is no 2.131(3) and 2.138(3) Å. In compounds [ReOCl(N–O)2], the
clear explanation for the different ligand orientation of Re–N bond trans to the chloride ion is shorter than the Re–
complex 6 relative to compounds 7–10. The studies have N bond trans to the oxygen atom of the chelating ligand. It
shown that even small changes in the steric and electronic seems to be due to the stronger π donation of the chloride
properties of the ligand can have a significant impact on ion. For all reported complexes the Re–N bonds are signifi-
the stereochemistry of the resulting compounds.
cantly longer than the Re–O distances.
6
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Job/Unit: I20277
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Pages: 11
Oxidorhenium(V) Complexes
Catalytic Epoxidation Experiments
cause of the different electronic properties. The carboxylate
oxidorhenium(V) complexes gave comparable conversion of
the alkene into the epoxide with a yield only slightly lower
than the complexes that incorporate benzoxazole and the
benzothiazole ligand (3 and 4), for which the best yield was
observed. The highest selectivity (Ͼ99%) in catalytic epox-
idation experiments was found with 7 and 8, for which no
side products could be detected (below the threshold of the
GC–MS integration routine). Slightly higher catalytic per-
formance with regard to substrate conversion was shown by
7 with a yield of cyOxide of 62% after 21 h in comparison
to 8 with 55%. Furthermore, with catalyst 8, an induction
period was observed. All other complexes (2–6, 9, and 10)
revealed variable amounts of side products (2–15%), usu-
ally the ring-opened product by water, cyclooctane-1,2-diole
(cyDiole). Only with complex 2, which contained a benzo-
triazole ligand, could the formation of an additional side
product be observed (11% cyOtBu after 21 h). Its mass
spectrum is consistent with tert-butoxycyclooctane, presum-
ably formed through a ring-opening by tert-butyl alcohol.
This is in line with the observed 10% decrease of cyOxide
with time (60% after 5 h and 50% after 21 h). In general,
all observed yields are in a similar range, thereby impeding
a detailed structure/activity correlation. Apparently, the
electronic and steric environments imposed by the investi-
gated ligands lead to similar rhenium centers. This is appar-
ent when comparing compounds 7 and 9, which differ only
in one anionic ligand (methoxy versus chloro). However,
the two complexes 2 and 6 display a superior initial activity
(61% after 5 h for 2 and 56% after 2.75 h for 6). It is worth
noting that 2 is the only compound among the phenoxide
group with an additional methyl substituent, and 6 is the
only one with a trans MeO–Re=O orientation. With the
rhenium(V) catalyst, no full conversion has been observed
thus far, presumably due to both catalase activity and cata-
lyst deactivation.[8–16] Apparently, the better donor proper-
ties of hmpbta in 2 and the trans orientation in 6 have a
beneficial influence on the catalytic yield. Therefore, future
complex design will include trans-oriented complexes with
ligands that have superior donor properties.
All ten oxidorhenium(V) complexes 1–10 were tested in
the epoxidation of cyclooctene (cyOct). Epoxidation experi-
ments were done with 1 mol-% of the respective complex at
50 °C in CHCl3 using tert-butyl hydrogenperoxide (TBHP;
3 equiv.) for a time between 20–27 h (Scheme 6).
Scheme 6. Epoxidation of cyclooctene.
Out of the 10 complexes, 1, which is equipped with benz-
imidazole ligands, showed the lowest conversion of only
3%, respectively, with a very long induction period (Ͼ3 h).
All other complexes 2–10 reached yields of cyclooctane ox-
ide (cyOxid) between 58 and 75% (Table 6).
Table 6. Catalytic performance of complexes 2–10 in the epoxid-
ation of cyclooctene.
Cat.
t
cyOxid
[%]
Selectivity
of epoxide
[%]
Side
product
[%]
[h]
2
3
5
21
61
50
84
5[a]
11[b]
0.5
3
20
27
16
36
62
74
97
3[a]
4
1
3
7.5
23
4
96
4[a]
22
59
75
5
6
1
4
24
16
33
61
95
5[a]
1
2.75
19
33
56
69
68
Ͼ99
–
25
7
0.5
5
21
4
26
62
Ͼ99
–
Conclusion
8
9
3
22
13
55
Ͼ99
–
A series of oxidorhenium(V) complexes that incorporate
phenolate and carboxylate ligands were synthesized, char-
acterized, and utilized as catalyst in the epoxidation of cy-
clooctene. The metal precursors [ReO2(py)4]Cl turned out
to be an excellent starting material for the preparation of
[ReOX(N–O)2] complexes with carboxylate ligands. One of
the reported [ReOX(N–O)2] complexes shows a very rare
trans-N,N and trans-O,O ligand arrangement. Except for 1,
the compounds show good catalytic activity and selectivity
in the epoxidation of cyclooctene with tert-butyl hydroper-
oxide. The yield of cyclooctane oxide varies between 58 and
0.5
5
21
4
21
58
98
2[a]
10
0.5
5
21
22
41
59
98
2[a]
[a] Side product: cyclooctane-1,2-diole (cyDiole). [b] Side product:
tert-butoxycyclooctane (cyOtBu).
The catalytic performances of the oxidorhenium(V) com- 75%, which is comparable to previously reported oxidorhe-
plexes that incorporate phenolate ligands were found to be nium(V) systems, but lower than rhenium(VII) compounds.
strongly influenced by the heterocycle ring, most likely be- Interestingly, the highest initial activity was displayed by an
Eur. J. Inorg. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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7

Job/Unit: I20277
/KAP1
Date: 28-06-12 18:07:49
Pages: 11
B. Machura et al.
FULL PAPER
General Procedure for the Preparation of Rhenium Complexes 1–5:
[ReOX3(OPPh3)(SMe2)] (0.77 mmol) was suspended in methanol
(80 mL) and phenol-based ligand (1.54 mmol) was added. The sus-
pension was stirred at ambient temperature for 48 h and filtered,
thus yielding a green solid, which was washed with ethanol and
diethyl ether and then recrystallized.
unusual trans-N,N and trans-O,O isomer of [ReOX(N–O)2],
thus indicating that different region isomers might have a
significant influence on catalyst activity.
[ReOCl(hpbi)2]·THF (1): The compound was prepared according
to the general procedure by employing hpbi (0.32 g, 1.54 mmol)
and [ReOCl3(OPPh3)(SMe2)] (0.50 g, 0.77 mmol) to give 1 (0.34 g,
Experimental Section
Materials: All chemicals were purchased from commercial sources
and were used without further purification. [ReOCl3(OPPh3)-
(SMe2)] and [ReO2(py)4]Cl were prepared according to previously
published methods.[31–33]
1
61%). Recrystallization from methanol/tetrahydrofuran. H NMR
(400 MHz, [D6]DMSO): δ = 13.80 (s, 1 H), 13.64 (s, 1 H), 8.08–
8.00 (m, 2 H), 7.77 (d, J = 8.0 Hz, 1 H), 7.62–7.55 (m, 2 H), 7.49
(t, J = 7.6 Hz, 1 H), 7.42 (dd, J = 7.9, 1.4 Hz, 1 H), 7.35 (d, J =
8.0 Hz, 1 H), 7.24 (d, J = 7.4 Hz, 1 H), 7.07 (t, J = 7.5 Hz, 1 H),
7.04–6.96 (m, 2 H), 6.81 (t, J = 7.5 Hz, 1 H), 6.69 (t, J = 7.1 Hz,
1 H), 6.14 (d, J = 8.3 Hz, 1 H), 6.04 (d, J = 7.5 Hz, 1 H), 3.64–
3.58 (m 4 H), 1.79–1.73 (m, 4 H) ppm. 13C NMR (100 MHz, [D6]-
DMSO): δ = 167.5, 161.2, 154.3, 141.6, 140.4, 133.8, 133.7, 131.4,
131.3, 130.9, 130.4, 129.0, 128.9, 128.4, 127.7, 125.6, 124.7, 123.8,
123.2, 120.4, 119.6, 119.4, 119.0, 114.9, 112.9, 112.7, 49.08,
21.8 ppm. C30H26Cl1N4O4Re (728.20): calcd. C 49.44, H 3.57, N
Instrumentation: IR spectra were recorded with a Nicolet Magna
560 spectrophotometer in the spectral range 4000–400 cm–1 with
the samples in the form of KBr pellets. The 1H and 13C NMR
spectra were recorded (295 K) with a Bruker Avance 400 NMR
spectrometer at a resonance frequency of 400 MHz for 1H NMR
spectra and 100 MHz for 13C NMR spectra by using [D6]DMSO
or CDCl3 as solvent and TMS as an internal solvent. ESI–MS was
performed with a Varian 500-MS IT mass spectrometer ion trap
apparatus. The instrument was operating in the positive-ion mode
with a capillary voltage of 20 V, needle voltage of 5 kV, and a spray
shield voltage of 600 V. The drying gas (N2) temperature was
150 °C. The single-crystal X-ray diffraction measurement was car-
ried out with a Gemini A Ultra diffractometer equipped with an
Atlas CCD detector. Intensities of reflections were measured using
graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å) with ω
scan mode at room temperature. During the data reduction, Lo-
rentz, polarization, and empirical absorption correction using
spherical harmonics, implemented in the SCALE3 ABSPACK scal-
ing algorithm, were applied.[34] The structures were solved by Pat-
terson synthesis using SHELXS-97[35] and refined on F2 by full-
matrix least-square techniques using the SHELXTL-97[36] pro-
gram. The non-hydrogen atoms of the complexes were refined with
anisotropic temperature parameters. The hydrogen atoms bound to
carbon atoms were placed in calculated positions and treated as
riding on their parent atoms with d(C–H) = 0.93 Å, Uiso(H) = 1.2
Ueq(C) (aromtic); and d(C–H) = 0.96 Å, Uiso(H) = 1.5 Ueq(C)
(methyl). The methyl groups were allowed to rotate about their
local threefold axis.
7.69; found C 48.32, H 3.03, N 8.24. IR (KBr): ν = 3190 [ν(N–H)];
˜
1622, 1603, 1578 and 1538 ν(C=N) and ν(C=C); 960 ν(Re=O)
cm–1. ESI+-MS (MeOH): m/z = 437.62 [{ReO(hpbi)} + Na +
2H]+, 621.57 [{ReO(hpbi)2}]+, 643.63 [{ReO(hpbi)2} + Na]+,
655.65 [{ReOCl(hpbi)2}]+, 675.61 [{ReO(hpbi)2}
MeOH]+, 728.10 [{ReOCl(hpbi)2} + THF]+.
+
Na
+
[ReOCl(hmpbta)2] (2): The compound was prepared according to
the general procedure by employing hmpbta (0.35 g, 1.54 mmol)
and [ReOCl3(OPPh3)(SMe2)] (0.50 g, 0.77 mmol) to give 2 (0.34 g,
66%). Recrystallization from methanol/acetonitrile. 1H NMR
(400 MHz, CDCl3): δ = 8.47 (d, J = 8.8 Hz, 1 H), 8.35 (d, J =
1.2 Hz, 1 H), 8.02 (d, J = 8.7 Hz, 1 H), 7.84–7.80 (m, 1 H), 7.76
(d, J = 8.6 Hz, 1 H), 7.60–7.55 (m, 3 H), 7.42–7.37 (m, 1 H), 7.35–
7.31 (m, 1 H), 7.14–7.10 (m, 1 H), 6.75 (dd, J = 8.4, 1.6 Hz, 1 H)
6.34 (d, J = 8.8 Hz, 1 H), 6.22 (d, J = 8.4 Hz, 1 H), 2.58 (s, 3 H),
2.05 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 160.0, 151.4,
146.0, 145.4, 143.3, 142.6, 132.8, 132.8, 132.6, 131.8, 130.7, 130.6,
128.1, 127.8, 127.2, 125.7, 125.2, 121.6, 121.4, 120.1, 119.3, 119.0,
118.6, 114.3, 20.6, 20.5 ppm. C26H20Cl1N6O3Re (686.13): calcd. C
45.47, H 2.91, N 12.24; found C 44.97, H 2.73, N 12.87. IR (KBr):
CCDC-858621 (for 1), -858622 (for 3), -858623 (for 4), -858624
(for 5), -858625 (for 6), -858626 (for 7), -858627 (for 8), -858628
(for 9), and -858629 (for 10) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
ν = 1612, 1572 and 1504 ν(C=N) and ν(C=C); 957 ν(Re=O) cm–1.
˜
ESI+-MS (MeOH): m/z = 651.66 [{ReO(hmpbta)2}]+, 675.76
[{ReO(hmpbta)2} + Na + H]+, 709.54 [{ReOCl(hmpbta)2} +
Na]+, 1394.16 [{ReOCl(hmpbta)2}2 + Na]+.
[ReOCl(hpbo)2] (3): The compound was prepared according to the
general procedure by employing hpbo (0.33 g, 1.54 mmol) and
[ReOCl3(OPPh3)(SMe2)] (0.50 g, 0.77 mmol) to give 3 (0.33 g,
65%). Recrystallization from methanol/acetonitrile. 1H NMR
(400 MHz, CDCl3): δ = 8.32–8.28 (m, 1 H), 8.16 (dd, J = 8.0,
1.6 Hz, 1 H), 7.81 (dd, J = 7.3, 1.5 Hz, 1 H), 7.73–7.66 (m, 3 H),
7.64–7.60 (m, 2 H), 7.44 (d, J = 8.2 Hz, 1 H), 7.25–7.20 (m, 1 H),
7.09–7.00 (m, 3 H), 6.83–6.79 (m, 1 H), 6.55 (d, J = 7.9 Hz, 1 H),
6.49 (d, J = 8.4 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
173.1, 166.8, 164.7, 164.5, 149.2, 149.1, 143.0, 140.2, 137.2, 136.2,
128.9, 128.0, 127.4, 126.9, 126.6, 126.1, 124.6, 121.2, 121.1, 119.1,
118.9, 115.7, 111.5, 111.3, 110.7, 108.9 ppm. C26H16Cl1N2O5Re
(658.06): calcd. C 47.41, H 2.43, N 4.25; found C 49.70, H 2.93, N
General Epoxidation Procedure: Epoxidation experiments were car-
ried out with 1 mol-% of the respective complex at 50 °C in CHCl3
by using TBHP (3 equiv.) for a time between 20 and 27 h. Progress
was analyzed by GC–MS using Mesitylene as internal standard.
Yields were calculated in relation to cyclooctene (cyOct) conver-
sion. In a typical experiment, the respective catalyst (1–1.5 mg) was
dissolved in CHCl3 (2 mL) in a Mininert vial, and the calculated
amount of cyOct (which resulted in 1 mol-% catalyst loading) was
added with a syringe, capped, and heated to 50 °C. Then TBHP
(3 equiv. with respect to cyOct) was added through the septum and
stirred. For GC–MS analysis, samples (10 μL) were withdrawn at
different times and diluted to 1 mL with ethyl acetate that con-
tained 50 ppb mesitylene as internal standard. All solvents as well
as reagents were used as received. GC–MS measurements were per-
formed with an Agilent 7890 A with an Agilent 19091J–433 column
coupled to a mass spectrometer type Agilent 5975 C.
3.61. IR (KBr): ν = 1607, 1567 and 1535 ν(C=N) and ν(C=C); 958
˜
ν(Re=O) cm–1. ESI+-MS (MeOH): m/z = 623.47 [{ReO(hpbo)2}]+,
647.52 [{ReO(hpbo)2} + Na]+, 677.56 [{ReOCl(hpbo)2} + NH4]+,
681.45 [{ReOCl(hpbo)2} + Na]+, 1333.69 [{ReOCl(hpbo)2}2
NH4]+.
+
8
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Job/Unit: I20277
/KAP1
Date: 28-06-12 18:07:49
Pages: 11
Oxidorhenium(V) Complexes
[ReOCl(hpbt)2]·2MeCN (4): The compound was prepared accord-
ing to the general procedure by employing hpbt (0.35 g, 1.54 mmol)
and [ReOCl3(OPPh3)(SMe2)] (0.50 g, 0.77 mmol) to give 4 (0.41 g,
68%). Recrystallization from methanol/acetonitrile. 1H NMR
(400 MHz, CDCl3): δ = 8.79 (d, J = 8.1 Hz, 1 H), 7.99 (d, J =
(d, J = 5.3 Hz, 1 H), 8.54–8.48 (m, 2 H), 8.24–8.22 (m, 1 H), 8.23
(dd, J = 7.7, 0.7 Hz, 1 H), 8.09–8.05 (m, 1 H), 8.00–7.92 (m, 2 H),
4.55 (s, 3 H) ppm. C13H11N2O6Re (477.44): calcd. C 32.67, H 2.30,
N 5.86; found C 32.65, H 2.10, N 5.86. IR (KBr): ν = 1712 and
˜
1676 ν(COO)asym; 1609 ν(C=N) and ν(C=C); 1317 and 1287
7.8 Hz, 1 H), 7.80–7.68 (m, 3 H), 7.66–7.60 (m, 1 H), 7.57–7.54 (m, ν(COO)sym
;
984 ν(Re=O); 573 ν(Re–OMe) cm–1. ESI+-MS
2 H), 7.23–7.16 (m, 2 H), 7.08–7.01 (m, 2 H), 7.00–6.94 (m, 1 H),
6.92–6.87 (m, 1 H), 6.65 (t, J = 7.6 Hz, 1 H), 6.44 (d, J = 8.2 Hz,
1 H), 2.52 (s, 3 H), 2.50 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 171.9, 168.0, 161.5, 155.0, 153.1, 136.0, 135.5, 130.8,
130.1, 129.5, 129.1, 129.0, 127.5, 127.1, 126.8, 126.6, 126.3, 124.9,
121.9, 121.5, 121.4, 120.8, 119.5, 119.3, 118.2, 117.6, 116.4, 114.8,
30.9, 2.1 ppm. C30H22ClN4O3ReS2 (772.29): calcd. C 46.61, H 2.85,
(MeOH): m/z = 447.43 [{ReO(pic)2}]+, 501.36 [{ReO(OMe)(pic)2}
+ Na]+, 977.49 [{ReO(OMe)(pic)2}2 + Na]+.
[ReO(OMe)(2,5-dipic)2]·C5H5N (8): The compound was prepared
according to the general procedure by employing 2,5-dipic (0.30 g,
1.80 mmol) and [ReO2(py)4]Cl (0.50 g, 0.90 mmol) to give 8 (0.42 g,
73%). 1H NMR (400 MHz, [D6]DMSO): δ = 9.15 (dd, J = 2.1,
0.7 Hz, 1 H), 8.74 (d, J = 4.9 Hz, 1 H), 8.43 (dd, J = 8.1, 2.1 Hz,
2 H), 8.15 (dd, J = 8.1, 0.7 Hz, 2 H), 7.74–7.66 (m, 1 H), 2.09 (s,
3 H) ppm. C20H16N3O10Re (644.56): calcd. C 37.23, H 2.48, N
N 7.25; found C 42.51, H 2.03, N 3.66. IR (KBr): ν = 1599 and
˜
1557 ν(C=N) and ν(C=C); 960 ν(Re=O) cm–1. ESI+-MS (MeOH):
m/z = 655.45 [{ReO(hpbt)2}]+, 679.50 [{ReO(hpbt)2} + Na + H]+,
709.54 [{ReOCl(hpbt)2} + NH4 + H]+, 713.43 [{ReOCl(hpbt)2} +
Na]+, 1397.61 [{ReOCl(hpbt)2}2 + NH4]+.
6.52; found C 36.30, H 2.17, N 6.37. IR (KBr): ν = 1716 and 1685
˜
ν(COO)asym; 1565 ν(C=N) and ν(C=C); 1299 and 1289 ν(COO)sym
;
980 ν(Re=O); 570 ν(Re–OMe) cm–1. ESI+-MS (MeOH + AcOH):
m/z
= 415.25 [{ReO(OMe)} + Na +
2C5H5N]+, 437.37
[ReOBr(hmpbta)2] (5): The compound was prepared according to
the general procedure by employing hmpbta (0.29 g, 1.28 mmol)
and [ReOBr3(OPPh3)(SMe2)] (0.60 g, 0.64 mmol) to give 5 (0.32 g,
57%). Recrystallization from methanol/acetonitrile. 1H NMR
(400 MHz, CDCl3): δ = 8.53 (d, J = 8.8 Hz, 1 H), 8.33 (s, 1 H),
8.00 (d, J = 8.7 Hz, 1 H), 7.85–7.79 (m, 1 H), 7.76 (d, J = 8.6 Hz,
1 H), 7.62–7.52 (m, 3 H), 7.41–7.35 (m, 1 H), 7.35–7.29 (m, 1 H),
7.14–7.07 (m, 1 H), 6.75 (d, J = 8.3 Hz, 1 H), 6.29 (d, J = 8.8 Hz,
1 H), 6.23 (d, J = 8.4 Hz, 1 H), 2.58 (s, 3 H), 2.04 (s, 3 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 159.9, 151.1, 145.8, 145.6, 143.3,
142.5, 132.8, 132.7, 132.6, 131.8, 130.7, 130.6, 128.1, 127.8, 127.3,
125.6, 125.2, 121.5, 121.5, 120.1, 119.3, 119.1, 119.0, 114.1, 20.6,
20.5 ppm. C26H20Br1N6O3Re (730.59): calcd. C 42.70, H 2.74, N
[{ReO(OMe)(py)2} + K]+, 573.23 [{ReO(py)2} + K]+.
General Procedure for the Preparation of Rhenium Complexes 9 and
10: [ReOCl3(OPPh3)(SMe2)] (0.77 mmol) was suspended in meth-
anol or acetonitrile (80 mL) and the corresponding carboxylic acid
(1.54 mmol) was added. The suspension was stirred at ambient
temperature for 48 h and filtered, thereby yielding a blue solid,
which was washed with ethanol and diethyl ether and then recrys-
tallized.
[ReOCl(pic)2] (9): The compound was prepared according to the
general procedure by employing pic (0.19 g, 1.54 mmol) and
[ReOCl3(OPPh3)(SMe)2] (0.50 g, 0.77 mmol) to give 9 (0.28 g,
1
11.50; found C 42.87, H 2.50, N 11.49. IR (KBr): ν = 1612, 1571
˜
77%). H NMR (400 MHz, [D6]DMSO): δ = 9.02 (d, J = 5.5 Hz,
and 1504 ν(C=N) and ν(C=C); 956 ν(Re=O) cm–1. ESI+-MS
1 H), 8.69 (d, J = 5.4 Hz, 1 H), 8.64 (d, J = 3.6 Hz, 2 H), 8.30 (d,
J = 7.6 Hz, 1 H), 8.19 (t, J = 6.0 Hz, 1 H), 8.12–8.02 (m, 2 H)
ppm. 13C NMR (100 MHz, [D6]DMSO): δ = 180.7, 164.3, 158.2,
151.7, 148.6, 147.2, 146.2, 143.4, 132.4, 129.6, 127.4, 126.1 ppm.
C12H8ClN2O5Re (481.85): calcd. C 29.88, H 1.66, N 5.81; found C
(MeOH): m/z
= 528.36 [{ReO(hmpbta)} +
Na]+, 621.32
[{ReO(hmpbta)2} – 2CH3]+, 675.46 [{ReO(hmpbta)2} + Na]+,
752.21 [{ReOBr(hmpbta)2} + Na]+.
General Procedure for the Preparation of Rhenium Complexes 6–
8: A mixture of [ReO2(py)4]Cl (0.90 mmol) and the corresponding
carboxylic acid (1.80 mmol) in methanol (80 mL) was heated at
reflux for 30 min and allowed to cool to ambient temperature. The
resulting dark red suspension was filtered and the reddish-brown
microcrystalline precipitate was washed with methanol and diethyl
ether.
29.98, H 1.44, N 5.92. IR (KBr): ν = 1712 and 1669 ν(COO)
;
;
˜
asym
1609 and 1570 ν(C=N) and ν(C=C); 1317 and 1287 ν(COO)sym
984 ν(Re=O) cm–1. ESI+-MS (MeOH): m/z = 447.48 [{ReO-
(pic)2}]+, 501.41 [{ReO(OMe)(pic)2} + Na]+, 977.35 [{ReO(OMe)-
(pic)2}2 + Na]+.
[ReOCl(3-ind)2]·CH3OH (10): The compound was prepared ac-
cording to the general procedure by employing pic (0.25 g,
1.54 mmol) and [ReOCl3(OPPh3)(SMe)2] (0.50 g, 0.77 mmol) to
[ReO(OMe)(quin)2] (6): The compound was prepared according to
the general procedure by employing quin (0.31 g, 1.80 mmol) and
[ReO2(py)4]Cl (0.50 g, 0.90 mmol) to give 6 (0.38 g, 75%). 1H
NMR (400 MHz, CDCl3): δ = 9.76 (d, J = 8.9 Hz, 2 H), 8.83 (d,
J = 8.3 Hz, 2 H), 8.73 (d, J = 8.3 Hz, 2 H), 8.27 (ddd, J = 8.6, 6.9,
1.5 Hz, 2 H), 8.12 (d, J = 7.0 Hz, 2 H), 7.99–7.90 (m, 2 H), 3.08
(s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 182.3, 150.2,
150.0, 144.4, 134.9, 130.7, 130.2, 128.9, 128.4, 121.9, 57.6 ppm.
C21H15N2O6Re (577.55): calcd. C 43.62, H 2.60, N 4.85; found C
1
give 10 (0.34 g, 74%). H NMR (400 MHz, [D6]DMSO): δ = 8.10
(d, J = 8.0 Hz, 1 H), 7.90 (d, J = 7.5 Hz, 1 H), 7.85 (d, J = 7.0 Hz,
1 H), 7.73 (d, J = 8.4 Hz, 1 H), 7.50–7.35 (m, 4 H), 3.62 (s, 1 H),
2.08 (s, 3 H) ppm. C17H14Cl1N4O6Re (591.97): calcd. C 34.46, H
2.36, N 9.46; found C 35.89, H 2.01, N 11.46. IR (KBr): ν = 3109
˜
ν(N–H); 1725 and 1685 ν(COO)asym; 1630 and 1583 ν(C=N) and
ν(C=C); 1388 and 1366 ν(COO)sym; 990 ν(Re=O) cm–1. ESI+-MS
(MeOH + AcOH): m/z = 415.35 [{ReOCl(ind)} + NH4]+, 421.43
[{ReOCl(ind)} + Na]+, 527.41 [{ReO(ind)2}]+.
43.37, H 2.26, N 4.71. IR (KBr): ν = 1683 ν(COO)asym; 1617, 1595,
˜
1569 and 1515 ν(C=N) and ν(C=C); 1323 ν(COO)sym; 955
ν(Re=O); 512 and 500 ν(Re–OMe) cm–1. ESI+-MS (MeOH): m/z =
428.45 [{ReO(OMe)(quin)}
+
Na]+, 547.33 [{ReO(quin)2}]+,
Acknowledgments
571.34 [{ReO(quin)2} + Na + H]+, 601.31 [{ReO(OMe)(quin)2} +
Na]+, 1176.69 [{ReO(OMe)(quin)2}2 + Na]+.
M. W. thanks the Österreichischer Austauschdienst (ÖAD) for sup-
porting his stay at the Institute of Chemistry, Karl-Franzens-Uni-
versity of Graz, Austria. This work was financed by the Polish
[ReO(OMe)(pic)2] (7): The compound was prepared according to
the general procedure by employing pic (0.22 g, 1.80 mmol) and
[ReO2(py)4]Cl (0.50 g, 0.90 mmol) to give 7 (0.29 g, 68%). 1H National Science Centre (NCN), under Grant No. 2011/03/N/ST5/
NMR (400 MHz, [D6]DMSO): δ = 8.74 (d, J = 5.6 Hz, 1 H), 8.67
04522.
Eur. J. Inorg. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
9

Job/Unit: I20277
/KAP1
Date: 28-06-12 18:07:49
Pages: 11
B. Machura et al.
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Published Online: ᭿
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Eur. J. Inorg. Chem. 0000, 0–0

Job/Unit: I20277
/KAP1
Date: 28-06-12 18:07:49
Pages: 11
Oxidorhenium(V) Complexes
Epoxidation Catalysis
Several oxidorhenium(V) complexes that
contain phenolate- and carboxylate-based
ligands were synthesized and characterized
by spectroscopic means and by X-ray crys-
tal structure analysis. The complexes are
air- and moisture-stable and show catalytic
activity for the epoxidation of cyclooctene.
B. Machura,* M. Wolff,
D. Tabak, J. A. Schachner,
N. C. Mösch-Zanetti ....................... 1–11
Oxidorhenium(V) Complexes with Phen-
olate- and Carboxylate-Based Ligands:
Structure and Catalytic Epoxidation
Keywords: Rhenium / Phenolate ligands /
Carboxylate ligands / Epoxidation
Eur. J. Inorg. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
11