Chromophoric lewis base adducts of methyltrioxorhenium: Synthesis, catalysis and photochemistry

Article abstract of DOI:10.1002/ejic.201000348

A series of chromophoric Lewis base adducts of methyltrioxorhenium (MTO) was examined. The ligands were pyridine derivatives with different size of the aromatic system and variable substituents, thus providing a variation of electronic and steric parameters. The complexes were fully characterised (UV/Vis, IR and NMR spectroscopy, single-crystal X-ray diffraction and elemental analysis) and their stability constants in dichloromethane were determined by means of UV/Vis spectroscopy. Moreover, this report presents a study of the influence of these N-donor ligands coordinated to MTO on the catalytic activity of epoxidation of 1-octene. Each compound was tested twice; in a catalytic reaction under exclusion of light and in daylight. No significant differences in catalytic performance were found. The behaviour of the complexes under irradiation with UV light viras investigated by means of ¹⁷O-NMR and UV/Vis spectroscopy. The herein exposed experiments aimed for probing potential beneficial effects of chromophoric N-donor ligands in MTO adducts, as they might activate the catalytic system by providing additional energy for weakening bonds that have to be broken during the catalytic cycle.

Full text of DOI:10.1002/ejic.201000348

FULL PAPER
DOI: 10.1002/ejic.201000348
Chromophoric Lewis Base Adducts of Methyltrioxorhenium: Synthesis,
Catalysis and Photochemistry
Simone A. Hauser,[a] Valentina Korinth,[b] Eberhardt Herdtweck,[a] Mirza Cokoja,[a]
Wolfgang A. Herrmann,[a] and Fritz E. Kühn*[a,b]
Keywords: Rhenium / Homogeneous catalysis / Photochemistry / Epoxidation / Stability constants
A series of chromophoric Lewis base adducts of methyl-
trioxorhenium (MTO) was examined. The ligands were pyr-
idine derivatives with different size of the aromatic system
Each compound was tested twice; in a catalytic reaction un-
der exclusion of light and in daylight. No significant differ-
ences in catalytic performance were found. The behaviour of
and variable substituents, thus providing a variation of elec- the complexes under irradiation with UV light was investi-
tronic and steric parameters. The complexes were fully char-
acterised (UV/Vis, IR and NMR spectroscopy, single-crystal
X-ray diffraction and elemental analysis) and their stability
constants in dichloromethane were determined by means of
UV/Vis spectroscopy. Moreover, this report presents a study
of the influence of these N-donor ligands coordinated to
MTO on the catalytic activity of epoxidation of 1-octene.
gated by means of 17O-NMR and UV/Vis spectroscopy. The
herein exposed experiments aimed for probing potential
beneficial effects of chromophoric N-donor ligands in MTO
adducts, as they might activate the catalytic system by pro-
viding additional energy for weakening bonds that have to
be broken during the catalytic cycle.
–
tion time, with subsequent formation of ReO4 and ReO3,
Introduction
at low and high concentrations.[20] Some years later, the
studies were extended to Lewis base adducts of MTO.
Interesting properties of these adducts were published,[22,23]
but no further research was conducted in this direction.
This prompted us to investigate the effect of a number of
novel chromophoric Lewis base adducts of MTO with re-
spect to the complex stability under irradiation with UV
light.
Much research has been dedicated to the chemistry of
methyltrioxorhenium (MTO) since its discovery by Beattie
and Jones[1] in the late 1970s and the improvement of the
synthesis by Herrmann and co-workers[2] some years later.
The latter group discovered the ability of MTO to act as a
versatile catalyst of various organic reactions.[3] MTO can
be used in several catalytic processes, for instance olefin me-
tathesis[4] and aldehyde olefination.[5] Most recently, MTO
has been successfully applied in deoxygenation of epox-
ides.[6] However, the most important and thus best studied
MTO-catalysed reaction is olefin epoxidation.[7–9] Due to
Results and Discussion
the strong Lewis acidity of the metal centre, undesired side Synthesis and Spectroscopic Characterisation
reactions such as ring opening and diol formation are usu-
A series of chromophoric pyridine derivatives (1–7, Fig-
ure 1) was synthesised and the coordination to MTO was
ally occurring. This can be prevented by addition of bases,
mostly pyridine, bipyridine or pyrazole and their deriva-
tives, as shown by Sharpless et al. and other groups.[8,10–19]
The photochemistry of MTO was for the first time under
examination in the early 1990s.[20,21] MTO solutions were
found to be very sensitive to UV light, the rhenium-carbon
bond was reported to be photolysed after a short irradia-
[a] Chair of Inorganic Chemistry, Catalysis Research Center,
Technische Universität München,
Lichtenbergstrasse 4, 85748 Garching, Germany
Fax: +49-89-289-13473
E-mail: fritz.kuehn@ch.tum.de
[b] Molecular Catalysis, Catalysis Research Center, Technische
Universität München,
Lichtenbergstrasse 4, 85748 Garching, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000348.
Figure 1. Overview of the pyridine derivatives employed as ligands
for coordination to MTO.
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F. E. Kühn et al.
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examined. Complexes 8–14 were formed by treatment of the methyl group to the rhenium centre. Complex 11, how-
MTO with ligands 1–7 in a 1:1 ratio in diethyl ether at room ever, exists in both cis and trans arrangements in the solid
temperature (Scheme 1). Subsequent cooling of the yellow state. Together with the finding that only one peak is visible
solution led to precipitation of yellow crystals, which were in the 17O-NMR spectrum, this strongly indicates that
isolated by filtration and purified by washing with n-hex- packing forces are responsible for the solid-state configura-
ane. The compounds obtained are stable to air, both in the tion, rather than electronic or steric ligand effects. More-
solid state and in dichloromethane solution.
over, this conclusion is in accordance with previously re-
ported data.[24]
Scheme 1. Adduct formation of MTO with pyridine derivatives in
solution.
Figure 2. PLATON view of the solid-state structure of complex 8.
The thermal ellipsoids are shown at the 50% probability level.
1
Selected H and 13C NMR spectroscopic data of com-
pounds 8–14 are shown in Table 1. The proton signals of
the MTO methyl group of the complexes are considerably
shifted to higher field, indicating the strength of the Re–N
bond.[15] The same effect is observed in the 13C NMR spec-
tra. The vicinal protons to the nitrogen of the ligand have
a different electronic environment, similar to the methyl
group of the MTO, which is manifested by a high-field shift
compared to the free ligand.
Table 3. Selected bond lengths for complexes 8–14 (trans configura-
tion) determined by single-crystal X-ray diffraction.
Re–N [Å]
Re–C [Å]
Re–O [Å]
MTO[a]
8
–
2.074(4)
2.113(7)
1.703(2)
1.712(3) 1.706(6)
1.726(7)
2.422(5)
9
2.445(5)
2.439(4)
2.438(5)
2.372(3)
2.439(3)
2.418(2)
2.417(3)
2.094(6)
2.099(5)
2.102(6)
2.112(4)
2.081(5)
2.091(3)
2.092(4)
1.718(4) 1.705(4)
1.707(4)
1.717(4) 1.716(3)
1.716(3)
1.711(3) 1.716(4)
1.720(3)
1.722(3) 1.719(3)
1.713(3)
1.714(3) 1.712(3)
1.714(3)
1.720(2) 1.711(2)
1.714(2)
1.716(4) 1.716(3)
1.722(3)
1.713(2) 2ϫ1.708(4)
1.706(3) 2ϫ1.694(4)
10[b]
Table 1. Selected 1H and 13C NMR spectroscopic data for com-
plexes 8–14 in CDCl3.
α-H ligand, 1H α-H adduct 1H, Re-CH3, 1H Re-CH3, 13
C
11[b]
δ [ppm]
δ [ppm]
δ [ppm]
δ [ppm]
MTO
8
9
10
11
12
13
14
–
–
2.67
2.03
1.92
1.96
2.13
2.00
1.97
1.98
19.0
24.7
25.1
24.0
24.4
24.9
24.8
24.4
8.51 (1)
8.55 (2)
8.58 (3)
8.59 (4)
8.63 (5)
8.63 (6)
8.65 (7)
8.29
8.20
8.26
8.34
8.33
8.31
8.32
12
13
14[b]
2.408(4)
2.392(4)
2.102(5)
2.101(5)
[a] Values taken from ref.[25]. [b] The values of the second crystallo-
graphically independent molecule are printed in italics.
In the IR spectra, a red-shift of Re = O bands compared
to free MTO is observable. This gives rise to an enhanced
electron density donated from the ligand to the Re centre,
causing weakening of the Re=O bond (see Table 2).
Determination of Formation Constants
Table 2. Characteristic IR vibrations of CH3ReO3 fragments (cm–1)
in 8–14.
The formation constants of the MTO – ligand adducts
8–14 were determined by means of UV/Vis spectroscopy.[26]
Scheme 1 shows the equilibrium that is established in pres-
ence of MTO and a pyridine derivative. According to Equa-
tion (1), which is derived from the Lambert–Beer law (path
length: 1 cm), the absorbance of the solution (Abs) changes
in function of the presence of free ligand (L), uncoordinated
MTO (M) and the MTO-ligand adduct (ML).
MTO
8
9
10
11
12
13
14 Assignment
998
965
934 936 931 n.o. n.o. 934 931 ReO3 sym str.
927 926 n.o.[a] 927 928 927 n.o. ReO3 asym str.
[a] Not observed.
X-ray Crystal Structure of Ligand 5 and Complexes 8–14
Abs = εL[L] + εM[M] + εML[ML]
(1)
The solid-state structure of the synthesised compounds 5
and 8–14 was measured; one example is shown in Figure 2.
The adduct concentration [ML] can be expressed using
Selected bond lengths are given in Table 3. With one excep- the formation constant (Keq) by taking into account the
tion (compound 11), the N-base ligand coordinates trans to molar balance [M]T = [M] + [ML], leading to Equation (2).
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Chromophoric Lewis Base Adducts of Methyltrioxorhenium
(2)
Above 330 nm, the absorbance of MTO is negligible, i.e.
εM ≈ 0.[27] If the absorbance of the free ligands at the chosen
wavelength can also be ignored, i.e. εL ≈ 0, then Equation
(3) can be used to calculate the formation constant.
(3)
The values of the adduct formation constants (Table 4)
are calculated by fitting of experimental absorbance data
to Equation (2) or (3). Figure 3 shows the change in the
absorption spectrum upon successive addition of MTO to
a ligand solution in CH2Cl2. In the case of the compound
10, complex formation can be noticed at 350 nm. Thus, the
values at this wavelength have been used for the curve fit-
ting according to Equation (3) (see Figure 4).
Figure 4. Curve fitting with Equation 3 for determination of for-
mation constant of complex 10.
complex 9 with that of complex 10. The steric effect ac-
counts for the difference in the value of the formation con-
stant of complex 13 and complex 14.
Application in Epoxidation Catalysis
Table 4. Formation constants of compounds 8–14 in CH2Cl2.
The performance of ligands 2–7 was tested in the
MTO-catalysed epoxidation of 1-octene with hydrogen per-
oxide. tert-Butylpyridine (tBu-Pyr) was chosen as a bench-
mark ligand. A catalyst:ligand:oxidant:substrate ratio of
1:5:150:100 was used in all experiments, unless stated other-
wise. The catalytic tests were performed at room tempera-
ture and twice with each ligand: once with exclusion of light
and once in light with the goal to establish a statement
about the supposed beneficial effect of chromophoric pyr-
idine derivatives with respect to the already known advan-
tages of simple pyridine derivatives in epoxidation catalysis
with MTO.[19] Further details are given in the Exp. Section.
No significant diol formation or formation of other by-
products could be observed.
Absorbance [nm]
Formation constant (Keq) [Lmol–1]
8
340
355
350
370
335
300
300
431Ϯ27
563Ϯ88
386Ϯ47
309Ϯ36
78Ϯ25
348Ϯ93
286Ϯ98
9
10
11
12
13
14
Table 5 summarises the turnover frequencies (TOF) of
the different catalytic systems tested. Maximum epoxide
yield is obtained after 24 h reaction time, with a substrate
conversion between 50 and 80% (Figure 5). tBu-Pyr shows
no significant advantage in catalytic performance compared
to the chromophoric pyridine derivatives. Moreover, it can
be noted that the advantage of running the catalytic reac-
tion under exclusion of light is negligible with either type
of pyridine ligand. The yields of 1-octene epoxide with the
ligand additives tested within this work are comparable to
Figure 3. Change in the absorption in function of complex forma-
tion (10). (a) free ligand ([3] = 0.1 m), successive addition of
1 equiv. of MTO, (k) ligand with 10 equiv. MTO.
Table 5. Turnover frequencies [mol(epoxide) mol(cat)–1 h–1] deter-
mined after 5 min.
Ligand
TOF
[h–1]
Yield [%], after 24 h with
exclusion of light
The values of the formation constants for complexes 8–
14 are comparable to those reported in literature.[26,28–30]
Moreover, the influence of both the electronic and steric
nature of the ligand can be seen. The stability of the ad-
ducts is higher when the ligand has electron-donating sub-
stituents and is less sterically crowded. The electronic effect
is nicely seen when comparing the formation constant of
2
63
44
65
46
49
41
35
76
69
69
65
73
72
71
3
4
5
6
7
tBu-Pyr
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F. E. Kühn et al.
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the yield achieved with MTO alone.[31] Nevertheless, they
are far from those obtained with 3-methylpyrazole or pyr-
azole under the same conditions.[31]
Figure 6. Time resolved 17O-NMR spectra of complex 11 before
(top) and after irradiation with UV light. The signal of the MTO
oxo moieties at δ = 879 ppm is broadened due to fluxional equilib-
rium of complex formation, whereas the sharp peak at δ = 563 ppm
Figure 5. 1-Octene epoxide yields with different ligands.
–
can be assigned [ReO4 ].
Photostability of the Synthesised Compounds
complex absorption as well as the absorbance pattern of
free MTO.[20] Upon photolytic degradation of MTO, the
ligand is protonated. Thus, its absorbance spectrum
changes by a shift of the maximum to 375 nm.
One aim of this work is to probe potential beneficial ef-
fect of chromophoric Lewis bases in MTO adducts. They
might activate the catalytic system by providing additional
energy for weakening bonds that have to be broken during
the catalytic cycle. However, photoinduced homolysis of the
Re–CH3 bond in solution is the most common way of de-
gradation of MTO.[20] Vogler et al. reported the photoas-
sisted isomerisation of 4-styrylpyridine, where the complex
remained intact, i.e. the MTO was not affected by UV-radi-
ation.[23] This led to the hypothesis that larger chromo-
phoric systems might lead to stable MTO Lewis base ad-
ducts on the one hand, and act as a photosensitisers on the
other hand. The most convenient approaches to study the
stability or the photo-induced degradation of the MTO ad-
ducts are 17O-NMR and UV/Vis spectroscopy.
For the NMR studies, a 0.1  solution of the complexes
in CDCl3 was used and treated with UV light (λ = 368 nm).
In a second experiment, a fivefold excess of ligand was
added to MTO, in order to mimic the reaction conditions
of the catalytic tests (vide supra). The chemical shift of the
oxygen atoms of the freshly synthesised complexes was
found to be between 865 ppm and 885 ppm which is consis-
tent with the reported literature values.[32,33] Upon irradia-
tion, already after 6 min a peak at δ = 563 ppm was de-
tected, which could be attributed to the perrhenate
anion.[32] This peak became more pronounced after longer
irradiation time (see Figure 6). There was no significant dif-
ference in stability of the MTO in the two experiments per-
formed. Noteworthy, all complexes synthesised in this work
have shown the same behaviour under irradiation with UV
light (see Supporting Information).
Figure 7. UV/Vis spectra of complex 11 in CH2Cl2 (c = 0.16 m).
(a) Initial spectrum; (b) after 20 min exposure to UV light; (c) after
60 min; (d) after 120 min, the decrease in intensity of the peak at
377 nm can be explained by precipitation of the perrhenate and
protonated ligand.
The above-mentioned experiments clearly show that both
the MTO and the ligands are affected by prolonged irradia-
tion with UV light. Thus, no additional stability is brought
to the adducts by the use of chromophoric pyridine deriva-
tives. Despite of the use of chromophoric pyridine deriva-
tives as ligands on MTO, the obtained adducts are not
stable to UV light. However, as described above, the cata-
lytic epoxidation is not influenced by light.
Conclusions
The UV/Vis spectra were recorded in CH2Cl2. A 0.1 
solution of selected complexes was irradiated with UV light
In this study, seven chromophoric pyridine derivatives
and several samples were taken. Figure 7 shows the spectral were prepared and treated with MTO to form seven Lewis
change over a time span of 2 h. Ligand absorption is very base adducts of MTO. They have been fully characterised
strong, it shows a maximum at 325 nm. It partially overlaps and tested as catalysts in the epoxidation of 1-octene with
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Chromophoric Lewis Base Adducts of Methyltrioxorhenium
C, -PhCHCHPyr-), 120.8 (2 C, NC2H2C2H2C-), 21.3 (1 C, -PhCH3)
ppm.
H2O2. With respect to the benchmark ligand tert-butylpyr-
idine, the presented ligands do not show any advantages
in the epoxidation of 1-octene, whether performed under
exclusion of light or in daylight (see Figure 5). Moreover,
the photochemistry of the complexes was studied by means
of UV/Vis and 17O-NMR spectroscopy. The chromophoric
ligands did not influence the adduct stability under UV ir-
radiation. Complex decomposition occurred through the re-
ported pathway,[20] as formation of the perrhenate anion
was already observable after a short irradiation time with
UV light (see Figure 6 and Figure 7).
4-[2-(4-Bromophenyl)ethenyl]pyridine (3): Yield 503 mg (78%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 8.58 [d, J(H,H) =
6.0 Hz, 2 H, NC2H2C2H2C-], 7.50 [d, J(H,H) = 8.4 Hz, 2 H,
-CC2H2C2H2CBr], 7.38 [d, J(H,H)
=
8.4 Hz,
2
H,
-CC2H2C2H2CBr], 7.34 [J(H,H) = 5.2 Hz, 2 H, NC2H2C2H2C-],
7.22 [d, J(H,H) = 16.4 Hz, 1 H, PyrCHCH-], 6.98 [d, J(H,H) =
16.4 Hz, 1 H, PyrCHCH-] ppm. 13C NMR (100.6 MHz, CDCl3,
25 °C):
δ = 150.30 (2 C, NC2H2C2H2C-), 144.23 (1 C,
NC2H2C2H2C-), 135.13 (1 C, -CC2H2C2H2CBr), 132.02 (2 C,
-CC2H2C2H2CBr), 131.87 (1 C, PyrCHCH-), 128.44 (2 C,
-CC2H2C2H2CBr), 126.76 (1 C, PyrCHCH-), 122.68 (1 C,
-CC2H2C2H2CBr), 120.85 (2 C, NC2H2C2H2C-) ppm.
1
Experimental Section
4-[2-(Biphenyl)ethenyl]pyridine (4): Yield 980 mg (83%). H NMR
(400 MHz, CDCl3, 25 °C): δ = 8.59 [d, J(H,H) = 8.0 Hz, 2 H,
NC2H2C2H2C-], 7.63 (m, 7 H, -CC2H2C2H2C-CC2H2C2H2CH),
7.46 [t, J(H,H) = 8.0 Hz, 2 H, -CC2H2C2H2CH], 7.39 (m, 2 H,
NC2H2C2H2C-), 7.35 [d, J(H,H) = 16.0 Hz, 1 H, Pyr-CHCH-Ph-
Ph], 7.06 [d, J(H,H) = 16.0 Hz, 1 H, Pyr-CHCH-Ph-Ph] ppm.
Materials and Methods: All experimental work was carried out
using standard Schlenk techniques under argon. Solvents were
dried by standard procedures (hexane and diethyl ether over Na/
benzophenone; CH2Cl2 over CaH2), distilled and stored under ar-
gon over molecular sieves. High resolution NMR spectra were mea-
sured with Bruker Avance DPX-400 (1H: 400 MHz; 13C:
100.6 MHz; 17O: 54.2 MHz), and JEOL NMR GX-400 (1H:
400 MHz; 13C: 100.6 MHz) spectrometers. The UV/Vis spectra
were recorded on a JASCO UV/Vis V-550 spectrophotometer and
the IR spectra on a Perkin–Elmer 1600 series FT-IR instrument.
Microanalyses of the obtained products were performed in the
Mikroanalytisches Labor of the Technical University of Munich,
Garching, Germany. MTO was synthesised according to literature
procedures.[34]
13C NMR (100.6 MHz, CDCl3, 25 °C):
δ = 150.20 (2 C,
NC2H2C2H2C-), 144.62 (1 C, NC2H2C2H2C-), 141.51 (1 C,
-CC2H2C2H2CH), 140.38 (1 C, -CC2H2C2H2C-CC2H2C2H2CH),
135.16 (1 C, -CC2H2C2H2C-CC2H2C2H2CH), 132.71 (1 C, Pyr-
CHCH-Ph-Ph), 128.85 (2 C, -CC2H2C2H2CH), 127.58 (1 C,
-CC2H2C2H2CH), 127.47 (4 C, -CC2H2C2H2C-CC2H2C2H2CH),
126.95 (2 C, -CC2H2C2H2C-CC2H2C2H2CH), 125.99 (1 C, Pyr-
CHCH-Ph-Ph), 120.83 (2 C, NC2H2C2H2C-) ppm.
4-[2-(4-Anthracenylphenyl)ethenyl]pyridine (5): Yield 880 mg (65%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 8.63 [d, J(H,H) = 4.9 Hz,
2 H], 8.52 (s, 1 H), 8.06 [d, J(H,H) = 8.6 Hz, 2 H], 7.77 [d, 3J(H,H)
= 8.6 Hz, 2 H], 7.69 [d, J(H,H) = 8.6 Hz, 2 H], 7.47 [t, J(H,H) =
8.6, 7.4 Hz, 7 H], 7.37 [t, 3J(H,H) = 7.4, 7.4 Hz, 2 H], 7.18 [d,
J(H,H) = 15.9 Hz, 1 H] ppm. 13C NMR (100.6 MHz, CDCl3,
25 °C): δ = 150.2 (2 C), 144.7 (1 C), 139.5 (1 C), 136.3 (1 C), 135.4
(1 C), 132.9 (1 C), 131.8 (2 C), 131.4 (2 C), 130.1 (2 C), 128.4 (1
C), 127.0 (3 C), 126.8 (1 C), 126.6 (2 C), 126.3 (2 C), 125.5 (1 C),
125.1 (2 C), 120.9 (2 C) ppm.
Ligand Synthesis: Ligands 1–3 were synthesised by treating a solu-
tion of 4-picoline (2.48 mmol) in THF at –60 °C with an equimolar
amount of lithium diisopropylamine in THF.[35] The alcoholate was
formed upon addition of the corresponding aldehyde, which was
subsequently eliminated by refluxing in concentrated acetic acid for
18 h to form the C–C double bond. Purification was done by col-
umn chromatography on silica gel. The synthesis of ligands 4–7
was based on the Suzuki cross coupling mechanism described by
Fu et al.[36] The heteroaryl boronic acid reacted with an aryl bro-
mide in refluxing dioxane, whereas the reaction was catalysed by
[Pd2(dba)3] (dba = dibenzylideneacetone), PCy3 and K3PO4 (aq.).
Subsequent purification steps included filtration, extraction of the
filtrate and column chromatography.
4-Tolylpyridine (6): Yield 193 mg (60%). 1H NMR (400 MHz,
CDCl3, 25 °C): δ = 8.63 [d, J(H,H) = 5.4 Hz, 2 H, NC2H2C2H2C-
], 7.53 [d, J(H,H) = 8.0 Hz, 2 H, NC2H2C2H2C-], 7.48 [d, J(H,H)
= 6.0 Hz, 2 H, -CC2H2C2H2CCH3], 7.28 [d, J(H,H) = 8.0 Hz, 2
H, -CC2H2C2H2CCH3], 2.40 (s, 3 H, -PhCH3) ppm. 13C NMR
(100.6 MHz, CDCl3, 25 °C): δ = 150.2 (2 C, NC2H2C2H2C-), 148.2
(1 C, NC2H2C2H2C-), 139.2 [1 C, -CC2H2C2H2C(CH3)], 135.2 [1
C, -CC2H2C2H2C(CH3)], 129.8 [2 C, -CC2H2C2H2C(CH3)], 126.8
[2 C, -CC2H2C2H2C(CH3)], 121.4 (2 C, NC2H2C2H2C-), 21.2 (1
C, -PhCH3) ppm.
4-Styrylpyridine (1): Yield 314 mg (70%). 1H NMR (400 MHz,
CDCl3, 25 °C): δ = 8.51 [d, J(H,H) = 4.8 Hz, 2 H, NC2H2C2H2C-
], 7.48 [d, J(H,H) = 7.4 Hz, 2 H, -CC2H2C2H2CH], 7.35–7.24 (m,
4 H, NC2H2C2H2C-CHCH-CC2H2C2H2CH), 7.21 [d, J(H,H) =
9.8 Hz, 2 H, -CC2H2C2H2CH], 6.96 [d, J(H,H) = 15.9 Hz, 1 H,
Pyr-CHCH-Ph] ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): δ =
150.2 (2 C), 144.6 (2 C), 136.2 (1 C), 133.2 (1 C), 128.8 (2 C), 128.7
(2 C), 127.0 (1 C), 126.0 (2 C), 120.8 (1 C) ppm.
1
4-(3,5-Dimethylphenyl)pyridine (7): Yield 450 mg (66%). H NMR
(400 MHz, CDCl3, 25 °C): δ = 8.65 [d, J(H,H) = 6.8 Hz, 2 H,
NC2H2C2H2C-], 7.50 [d, J(H,H) = 6.8 Hz, 2 H, NC2H2C2H2C-],
7.27 [s, 2 H, -CC2H2C2(CH3)2CH], 7.10 [s, 1 H, -CC2H2C2-
(CH3)2CH], 2.41 [s, 6 H, -CC2H2C2(CH3)2CH] ppm. 13C NMR
(100.6 MHz, CDCl3, 25 °C): δ = 150.15 (2 C, NC2H2C2H2C-),
148.65 (1 C, NC2H2C2H2C-), 138.71 [2 C, -CC2H2C2(CH3)2CH],
138.18 [1 C, -CC2H2C2(CH3)2CH], 130.67 [1 C, -CC2H2C2-
(CH3)2CH], 124.86 [2 C, -CC2H2C2(CH3)2CH], 121.69 (2 C,
NC2H2C2H2C-), 21.36 [2 C, -CC2H2C2(CH3)2CH] ppm.
4-[2-(4-Methylphenyl)ethenyl]pyridine (2): Yield 386 mg (80%). 1H
NMR (400 MHz, CDCl3, 25 °C): δ = 8.55 [d, J(H,H) = 6.0 Hz, 2
H, NC2H2C2H2C-], 7.43 [d, J(H,H) = 8.0 Hz, 2 H, NC2H2C2H2C-
], 7.34 [d, J(H,H) = 6.0 Hz, 2 H, -CC2H2C2H2CCH3], 7.27 [d,
J(H,H) = 13.6 Hz, 1 H, -PhCHCHPyr-], 7.18 [d, J(H,H) = 7.6 Hz,
2 H, -CC2H2C2H2CCH3], 6.95 [d, J(H,H) = 16.0 Hz, 1 H,
-PhCHCHPyr-], 2.37 (s, 3 H, -CC2H2C2H2CCH3) ppm. 13C NMR
(100.6 MHz, CDCl3, 25 °C): δ = 150.2 (1 C, NC2H2C2H2C-), 144.8
(2 C, NC2H2C2H2C-), 138.9 (1 C, -CC2H2C2H2CCH3), 133.4 Typical Procedure for the Preparation of the Chromophoric Lewis
(1 C, -CC2H2C2H2CCH3), 133.1 (1 C, -PhCHCHPyr-), 129.5 (2 Base Adducts of MTO: An equimolar amount of MTO and ligand
C, -CC2H2C2H2CCH3), 126.9 (2 C, -CC2H2C2H2CCH3), 124.9 (1 was dissolved in diethyl ether and the solution was stirred for 1 h
Eur. J. Inorg. Chem. 2010, 4083–4090
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4087

F. E. Kühn et al.
FULL PAPER
before cooling the mixture in an ice bath. A yellow precipitate
formed, which was filtered and washed with hexane. The solid was
dried in vacuo and analysed by standard analysis methods.
(506.57): calcd. C 47.40, H 3.58, N 2.77; found C 47.33, H 3.58, N
2.77.
{4-[2-(4-Anthracenylphenyl)ethenyl]pyridine}methyltrioxorhenium
1
Methyl(4-styrylpyridine)trioxorhenium (8): Yield 58 mg (76%). 1H
NMR (400 MHz, CDCl3, 25 °C): δ = 8.29 [d, J(H,H) = 6.2 Hz,
(12): Yield 87 mg (84%). H NMR (400 MHz, CDCl3, 25 °C): δ =
8.51 (s, 1 H), 8.33 [d, J(H,H) = 6.2 Hz, 2 H], 8.05 [d, J(H,H) =
8.3 Hz, 2 H], 7.76 [d, J(H,H) = 8.3 Hz, 2 H], 7.67 [d, J(H,H) =
8.7 Hz, 2 H], 7.47 (m, 7 H), 7.35 [m, J(H,H) = 15.6 Hz, 2 H], 7.15
[d, J(H,H) = 16.2 Hz, 1 H], 2.00 (s, 3 H, -ReCH3) ppm. 13C NMR
(100.6 MHz, CDCl3, 25 °C): δ = 148.2 (2 C), 146.7 (1 C), 140.0 (1
C), 136.1 (1 C), 135.0 (1 C), 134.6 (1 C), 132.0 (2 C), 131.4 (2 C),
130.1 (2 C), 128.4 (1 C), 127.2 (3 C), 126.9 (1 C), 126.5 (2 C), 125.6
(2 C), 125.4 (1 C), 125.2 (2 C), 121.7 (2 C), 24.9 (1 C, -ReCH3)
2
H, NC2H2C2H2C-], 7.54 [d, J(H,H)
= 7.4 Hz, 2 H,
-CC2H2C2H2CH], 7.45 (m, H, NC2H2C2H2C-CHCH-
6
CC2H2C2H2CH), 7.01 [d, J(H,H) = 17.2 Hz, 1 H, Pyr-CHCH-Ph],
2.03 (s, 3 H, -ReCH3) ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C):
δ = 147.2 (2 C), 135.6 (2 C), 135.5 (1 C), 129.3 (1 C), 128.9 (2 C),
127.3 (2 C), 124.7 (1 C), 121.9 (2 C), 24.7 (1 C) ppm. IR (KBr): ν
˜
= 1605 (vs), 1499 (w), 1449 (w), 1428 (w), 1384 (w), 1013 (m), 971
(m), 961 (w), 934 (vs), 927 (vs), 877 (w), 818 (m), 559 (w), 548 (m)
cm–1. C14H14NO3Re (430.47): calcd. C 39.06, H 3.28, N 3.25; found
C 39.56, H 3.31, N 3.34.
ppm. IR (KBr): ν = 3434 (w), 3050 (w), 1607 (s), 1592 (m), 1443
˜
(w), 1426 (m), 1412 (w), 1384 (m), 1066 (w), 1015 (m), 969 (w), 931
(vs), 881 (m), 827 (m), 790 (w), 735 (s), 653 (w), 635 (w), 613 (m),
568 (w), 554 (m) cm–1. 541 (m), 422 (w) cm–1. C28H22NO3Re
(606.69): calcd. C 55.41, H 3.66, N 2.31; found C 55.80, H 3.72, N
2.24.
Methyl{4-[2-(4-Methylphenyl)ethenyl]pyridine}trioxorhenium
(9):
1
Yield 53 mg (72%). H NMR (400 MHz, CDCl3, 25 °C): δ = 8.20
[d, J(H,H) = 5.4 Hz, 2 H, NC2H2C2H2C-], 7.42 (m, 4 H,
NC2H2C2H2C-, -CC2H2C2H2CCH3), 7.30 [d, J(H,H) = 16.2 Hz,
Methyl(4-tolylpyridine)trioxorhenium (13): Yield 67 mg (97%). 1H
NMR (400 MHz, CDCl3, 25 °C): δ = 8.31 [d, J(H,H) = 6.2 Hz, 2
H, NC2H2C2H2C-], 7.56 [d, J(H,H) = 6.2 Hz, 2 H, NC2H2C2H2C-
], 7.52 [d, J(H,H) = 7.9 Hz, 2 H, -CC2H2C2H2CCH3], 7.30 [d,
J(H,H) = 7.5 Hz, 2 H, -CC2H2C2H2CCH3], 2.41 (s, 3 H, -PhCH3),
1.97 (s, 3 H, -ReCH3) ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C):
δ = 151.1 (1 C), 147.1 (2 C), 140.3 (1 C), 133.8 (1 C), 130.0 (2 C),
126.9 (2 C), 122.5 (2 C), 24.8 (1 C, -ReCH3), 21.2 (1 C, Ph-CH3)
1
H, -PhCHCHPyr-], 7.20 [d, J(H,H)
=
7.9 Hz,
16.2 Hz,
2
1
H,
H,
-CC2H2C2H2CCH3], 6.93 [d, J(H,H)
=
-PhCHCHPyr-], 2.37 (s, 3 H, -PhCH3), 1.92 (s, 3 H, -ReCH3) ppm.
13C NMR (100.6 MHz, CDCl3, 25 °C):
δ
=
147.94 (1 C,
NC2H2C2H2C-), 147.06 (2 C, NC2H2C2H2C-), 139.66 (1 C,
-CC2H2C2H2CCH3), 135.48 (1 C, -CC2H2C2H2CCH3), 132.76 (1
C, -PhCHCHPyr-), 129.65 (2 C, -CC2H2C2H2CCH3), 127.23 (2 C,
-CC2H2C2H2CCH3), 123.52 (1 C, -PhCHCHPyr-), 121.85 (2 C,
NC2H2C2H2C-), 25.08 (1 C, -ReCH3), 21.36 (1 C, -PhCH3) ppm.
ppm. IR (KBr): ν = 33445 (m), 2925 (w), 1610 (s), 492 (m), 1384
˜
(m), 1262 (w), 1227 (w), 12211 (w), 1073 (m), 1037 (w), 1010 (m),
934 (vs), 927 (vs), 854 (w), 811 (s), 721 (m), 559 (m), 498 (m) cm–1.
C13H14NO3Re (418.46): calcd. C 37.31, H 3.37, N 3.35; found C
37.05, H 3.41, N 3.34.
IR (KBr): ν = 3434 (w), 3025 (w), 1636 (m), 1602 (vs), 1514 (m),
˜
1428 (m), 1384 (w), 1210 (w), 1183 (w), 1013 (s), 975 (m), 936 (vs),
926 (vs), 826 (s), 736 (w), 706 (w), 624 (m), 547 (s), 502 (m) cm–1.
C15H16NO3Re (444.50): calcd. C 40.53, H 3.63, N 3.15; found C
38.55, H 3.33, N 3.16.
[4-(3,5-Dimethylphenyl)pyridine]methyltrioxorhenium (14): Yield
106 mg (70%). 1H NMR (400 MHz, CDCl3, 25 °C): δ = 8.32 [d,
J(H,H) = 6.4 Hz, 2 H, NC2H2C2H2C-], 7.56 [d, J(H,H) = 6.6 Hz,
2 H, NC2H2C2H2C-], 7.21 [s, 2 H, -CC2H2C2(CH3)2CH], 7.11 [s, 1
H, -CC2H2C2(CH3)2CH], 2.39 [s, 6 H, -CC2H2C2(CH3)2CH], 1.98
(s, 3 H, -ReCH3) ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): δ =
151.4 (1 C), 147.2 (2 C), 139.0 (2 C), 136.8 (1 C), 131.5 (1 C), 125.0
{4-[2-(4-Bromophenyl)ethenyl]pyridine}methyltrioxorhenium
(10):
1
Yield 68 mg (79%). H NMR (400 MHz, CDCl3, 25 °C): δ = 8.26
[d, J(H,H) = 6.2 Hz, 2 H, NC2H2C2H2C-], 7.52 [d, J(H,H) =
8.3 Hz, 2 H, -CC2H2C2H2CBr], 7.41 (m, 4 H, NC2H2C2H2C-,
-CC2H2C2H2CBr), 7.25 [d, J(H,H) = 16.4 Hz, 1 H, Pyr-CHCH-],
6.98 [d, J(H,H) = 16.2 Hz, 1 H, Pyr-CHCH-], 1.96 (s, 3 H, -ReCH3)
ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): δ = 147.3 (2 C), 147.0
(1 C), 134.5 (1 C), 134.1 (1 C), 132.1 (3 C), 128.7 (2 C), 125.4 (1
(2 C), 122.8 (2 C), 24.4 (1 C), 21.3 (2 C) ppm. IR (KBr): ν = 3434
˜
(w), 2916 (w), 1613 (vs), 1551 (w), 1507 (w), 1408 (w), 1385 (w),
1232 (w), 1073 (m), 1021 (m), 931 (vs), 828 (s), 664 (m), 589 (m),
561 (m), 434 (w), 418 (w) cm–1. C14H16NO3Re (432.49): calcd. C
38.88, H 3.73, N 3.24; found C 38.88, H 3.73, N 3.24.
C), 123.5 (1 C), 122.0 (1 C), 24.0 (1 C) ppm. IR (KBr): ν = 3466
˜
(w), 3048 (w), 2973 (w), 1895 (w), 1773 (w), 1637 (m), 1610 (vs),
1586 (s), 1497 (m), 1483 (m), 1428 (s), 1393 (m), 1385 (m), 1209
(m), 1070 (vs), 1017 (vs), 1008 (s), 975 (s), 970 (s), 928 (vs), 883
(m), 875 (m), 829 (vs), 738 (w), 674 (w), 583 (m), 557 (s), 542 (s).
496 (w) cm–1. C14H13BrNO3Re (509.37): calcd. C 33.01, H 2.57, N
2.75; found C 32.88, H 2.53, N 2.78.
Single-Crystal X-ray Structure Determination of Compound 5:
C27H19N; Mr = 357.43; crystal colour and shape: colourless frag-
ment, crystal dimensions = 0.51ϫ0.56ϫ0.64 mm; crystal system:
monoclinic; space group: Cc (no. 9); a = 14.9971(6), b = 10.9497(4),
c = 12.4175(5) Å; β = 114.048(2)°; V = 1862.14(13) Å3; Z = 4; µ
(Mo-Kα) = 0.073 mm–1; ρcalcd. = 1.275 gcm–3; Θ range 2.38–25.34;
data collected: 32910; independent data [IoϾ2σ(Io)/all data/Rint]:
{4-[2-(Biphenyl)ethenyl]pyridine}methyltrioxorhenium (11): Yield
69 mg (80%). 1H NMR (400 MHz, CDCl3, 25 °C): δ = 8.34 [d,
3360/3397/0.023;
data/restraints/parameters:
3397/2/329;
J(H,H)
=
6.2 Hz,
2
H, NC2H2C2H2C-], 7.62 (m,
7.47–7.37 (m,
6
H,
H,
R1[IoϾ2σ(Io)/all data] = 0.0255/0.0258; wR2 [IoϾ2σ(Io)/all data] =
-CC2H2C2H2C-CC2H2C2H2CH),
5
0.0709/0.0713; GOF = 1.080; ∆ρmax/min = 0.13/–0.12 eÅ–3.
NC2H2C2H2C-, -CC2H2C2H2CH), 7.36 [d, J(H,H) = 16.2 Hz, 1 H,
Pyr-CHCH-Ph-Ph], 7.04 [d, J(H,H) = 16.2 Hz, 1 H, Pyr-CHCH-
Ph-Ph], 2.13 (s, 3 H, -ReCH3) ppm. 13C NMR (100.6 MHz, CDCl3,
25 °C): δ = 147.7 (2 C), 147.0 (1 C), 142.0 (1 C), 140.2 (1 C), 140.2
Single-Crystal X-ray Structure Determination of Compound 8:
C14H14NO3Re; Mr = 430.47; crystal colour and shape: yellow frag-
ment, crystal dimensions = 0.13ϫ0.18ϫ0.51 mm; crystal system:
(1 C), 134.6 (2 C), 128.9 (2 C), 127.7 (2 C), 127.6 (2 C), 127.0 (2 monoclinic; space group: P21 (no. 4); a = 9.0054(2), b = 7.2442(2),
C), 124.8 (1 C), 121.7 (2 C), 24.4 (1 C) ppm. IR (KBr): ν = 344 c = 11.0721(3) Å; β = 109.3284(11)°; V = 681.60(3) Å3; Z = 2; µ
˜
(w), 3032 (w), 1600 (s), 1487 (m), 1426 (m), 1204 (w), 1195 (w), (Mo-Kα) = 8.916 mm–1; ρcalcd. = 2.098 gcm–3; Θ range 1.95–25.39;
1015 (m), 976 (m), 934 (vs), 927 (vs), 879 (w), 836 (m), 765 (m), data collected: 10806; independent data [IoϾ2σ(Io)/all data/Rint]:
737 (w), 690 (m), 638 (w), 561 (m), 529 (w) cm–1. C20H18NO3Re
2275/2281/0.059;
data/restraints/parameters:
2281/1/173;
4088
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 4083–4090

Chromophoric Lewis Base Adducts of Methyltrioxorhenium
R1[IoϾ2σ(Io)/all data] = 0.0259/0.0259; wR2 [IoϾ2σ(Io)/all data] =
0.0648/0.0648; GOF = 1.090; ∆ρmax/min = 2.27/–2.57 eÅ–3.
collected: 35302; independent data [IoϾ2σ(Io)/all data/Rint]: 2592/
2741/0.048; data/restraints/parameters: 2741/0/195; R1[IoϾ2σ(Io)/
all data] = 0.0186/0.0200; wR2 [IoϾ2σ(Io)/all data] = 0.0410/0.0416;
GOF = 1.099; ∆ρmax/min = 1.09/–1.30 eÅ–3.
Single-Crystal X-ray Structure Determination of Compound 9:
C15H16NO3Re; Mr = 444.49; crystal colour and shape: yellow frag-
ment, crystal dimensions 0.15ϫ0.15ϫ0.43 mm; crystal system:
monoclinic; space group: P21/n (no. 14); a = 9.1661(4), b =
7.1741(3), c = 22.3772(9) Å; β = 97.795(2)°; V = 1457.89(11) Å3; Z
= 4; µ (Mo-Kα) = 8.341 mm–1; ρcalcd. = 2.025 gcm–3; Θ range 1.84–
25.36; data collected: 29722; independent data [IoϾ2σ(Io)/all data/
Rint]: 2423/2564/0.058; data/restraints/parameters: 2564/0/183;
R1[IoϾ2σ(Io)/all data] = 0.0289/0.0307; wR2 [IoϾ2σ(Io)/all data] =
0.0671/0.0680; GOF = 1.261; ∆ρmax/min = 0.85/–1.54 eÅ–3.
CCDC-777693 (for 5), -777694 (for 8), -777695 (9), -777696 (for
10), -777697 (for 11), -777698 (for 12), -777699 (for 13), and -77770
(for 14) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Formation Constant Measurements: An UV/Vis spectrophotometric
method was used to determine the formation constants of the chro-
mophoric Lewis base adducts of MTO. Aliquots of a 0.1 m solu-
tion of MTO in CH2Cl2 were successively added to a 0.1 m solu-
tion of the ligand in CH2Cl2 in a quartz cuvette (path length 1 cm,
total volume 3 mL). UV/Vis spectra of the homogeneous solutions
at equilibrium containing the metal complex, the ligand and the
adduct were recorded in the range of 200–400 nm before and after
each addition of the MTO aliquot. The values of the formation
constants were calculated by fitting the equilibrium absorbance at
a certain wavelength to Equation (2) or (3) according to the chosen
wavelength and the free ligand absorption using the IGOR com-
puter program.
Single-Crystal X-ray Structure Determination of Compound 10:
C14H13BrNO3Re; Mr = 509.36; crystal colour and shape: yellow
fragment, crystal dimensions 0.05ϫ0.13ϫ0.53 mm; crystal system:
¯
triclinic; space group: P1 (no. 2); a = 5.9849(2), b = 15.9131(6), c
= 17.0785(6) Å; α = 66.0608(15), β = 85.8488(15), γ = 86.3720(14)°;
V = 1481.68(9) Å3; Z = 4; µ (Mo-Kα) = 10.903 mm–1; ρcalcd.
=
2.283 gcm–3; Θ range 1.31–25.45; data collected: 18921; indepen-
dent data [IoϾ2σ(Io)/all data/Rint]: 4839/5188/0.042; data/restraints/
parameters: 5188/0/363; R1[IoϾ2σ(Io)/all data] = 0.0264/0.0286;
wR2 [IoϾ2σ(Io)/all data] = 0.0697/0.0721; GOF = 1.048; ∆ρmax/min
= 2.13/–1.85 eÅ–3.
Catalysis: In a typical experiment, 1-octene (0.628 mL, 4 mmol),
MTO (10 mg, 0.04 mmol), ligand (0.2 mmol), 0.200 mL of mesity-
lene (internal standard), 0.200 mL of toluene (internal standard)
and 2.45 mL of CH2Cl2 were added to the reaction vessel under
standard conditions at room temperature. The reaction started
upon addition of H2O2 (35% aqueous solution) (0.55 mL, 6 mmol)
under vigorous stirring. The course of the reaction was monitored
by quantitative GC analysis. Samples (0.2 mL) were taken at spe-
cific time intervals, treated with Na2SO3 to quench the excess of
peroxide and to remove water, filtered and diluted with dry CH2Cl2
before injection into a GC column. The conversion of 1-octene and
the formation of octene epoxide were calculated from calibration
curves (r2 = 0.999) recorded prior to the reaction course.
Single-Crystal X-ray Structure Determination of Compound 11:
C20H18NO3Re; Mr = 506.56; crystal colour and shape: yellow frag-
ment, crystal dimensions 0.24ϫ0.35ϫ0.38 mm; crystal system: tri-
¯
clinic; space group: P1 (no. 2); a = 5.7288(3), b = 11.4564(6), c =
27.4120(14) Å; α = 82.715(3), β = 89.200(2), γ = 77.895(2)°; V =
1744.74(16) Å3;
Z = 4; µ (Mo-Kα) = =
6.983 mm–1; ρcalcd.
1.929 gcm–3; Θ range 0.75–25.37; data collected: 69973; indepen-
dent data [IoϾ2σ(Io)/all data/Rint]: 5347/6039/0.070; data/restraints/
parameters: 6039/0/453; R1[IoϾ2σ(Io)/all data] = 0.0217/0.0279;
wR2 [IoϾ2σ(Io)/all data] = 0.0507/0.0538; GOF = 1.068; ∆ρmax/min
= 0.87/–0.52 eÅ–3.
Single-Crystal X-ray Structure Determination of Compound 12:
C28H22NO3Re; Mr = 606.68; crystal colour and shape: yellow frag-
ment, crystal dimensions 0.15ϫ0.18ϫ0.36 mm; crystal system: tri-
Testing the Photostability of the Complexes: Selected ligands were
treated with an equimolar amount of 17O-labelled MTO (prepared
by a published procedure[31]) or in a fivefold excess and the 1H and
17O NMR spectra were recorded. The adduct solutions (0.1  in
¯
clinic; space group: P1 (no. 2); a = 9.8694(3), b = 10.9626(4), c =
12.5154(7) Å; α = 99.490(2), β = 105.050(2), γ = 112.906(1)°; V =
1149.44(9) Å3;
Z = 2; µ (Mo-Kα) = =
5.316 mm–1; ρcalcd.
1
1.753 gcm–3; Θ range 1.77–25.44; data collected: 27800; indepen-
dent data [IoϾ2σ(Io)/all data/Rint]: 3917/3955/0.039; data/restraints/
parameters: 3955/0/299; R1[IoϾ2σ(Io)/all data] = 0.0139/0.0141;
wR2 [IoϾ2σ(Io)/all data] = 0.0356/0.0358; GOF = 1.078; ∆ρmax/min
= 1.12/–0.44 eÅ–3.
CDCl3) were then exposed to UV light and analysed again by H
and 17O NMR spectroscopy. For the UV/Vis analysis, a 0.1  solu-
tion of complex 11 in CH2Cl2 was prepared and exposed to UV
light. Samples were taken over a timespan of 2 h, diluted with
CH2Cl2 and the UV/Vis spectra were recorded.
Supporting Information (see also the footnote on the first page of
Single-Crystal X-ray Structure Determination of Compound 13:
C13H14NO3Re; Mr = 418.46; crystal colour and shape: yellow frag-
ment, crystal dimensions 0.15ϫ0.20ϫ0.38 mm; crystal system:
monoclinic; space group: P21/c (no. 14); a = 11.6924(4), b =
14.3708(4), c = 8.2219(3) Å; β = 110.3695(14)°; V = 1295.13(8) Å3;
Z = 4; µ (Mo-Kα) = 9.381 mm–1; ρcalcd. = 2.146 gcm–3; Θ range
1.86–25.39; data collected: 4902; independent data [IoϾ2σ(Io)/all
data/Rint]: 2196/2260/0.028; data/restraints/parameters: 2260/0/165;
R1[IoϾ2σ(Io)/all data] = 0.0218/0.0225; wR2 [IoϾ2σ(Io)/all data] =
0.0556/0.0561; GOF = 1.144; ∆ρmax/min = 1.12/–1.39 eÅ–3.
this article): UV/Vis spectra of ligands and complexes, spectro-
scopic data for the determination of the stability constants and 17
NMR spectra of selected complexes.
O
Acknowledgments
S. A. H. thanks the Bavarian elite network NanoCat for a Ph. D.
grant and for financial support of the project.
Single-Crystal X-ray Structure Determination of Compound 14:
C14H16NO3Re; Mr = 432.49; crystal colour and shape: yellow nee-
dle, crystal dimensions 0.03ϫ0.05ϫ0.23 mm; crystal system: mo-
noclinic; space group: P21/m (no. 11); a = 6.4763(9), b = 11.652(2),
c = 18.930(3) Å; β = 93.705(6)°; V = 1425.5(4) Å3; Z = 4; µ (Mo-
Kα) = 8.527 mm–1; ρcalcd. = 2.015 gcm–3; Θ range 1.08–25.37; data
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Received: March 29, 2010
Published Online: July 23, 2010
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