Trioxorhenium(VII) complexes with imidazolin-2-iminato ligands

Article abstract of DOI:10.1515/znb-2004-11-1220

The Staudinger reaction of the N-heterocyclic carbenes 1,3-di-tert- butylimidazolin-2-ylidene (1a), 1,3-dimesitylimidazolin-2-ylidene (1b) and 1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene (1c) with trimethylsilyl azide in boiling toluene furnishes the

Full text of DOI:10.1515/znb-2004-11-1220

Trioxorhenium(VII) Complexes with Imidazolin-2-iminato Ligands
Matthias Tamm, Stephan Beer, and Eberhardt Herdtweck
Lehrstuhl fu¨r Anorganische Chemie, Department Chemie der Technischen Universita¨t Mu¨nchen,
Lichtenbergstr. 4, D-85747 Garching bei Mu¨nchen, Germany
Reprint requests to Prof. Dr. M. Tamm. Fax: +49 (0)89-289-13473.
E-mail: matthias.tamm@ch.tum.de
Z. Naturforsch. 59b, 1497 – 1504 (2004); received August 26, 2004
Dedicated to Professor Hubert Schmidbaur on the occasion of his 70th birthday
The Staudinger reaction of the N-heterocyclic carbenes 1,3-di-tert-butylimidazolin-2-ylidene
(1a), 1,3-dimesitylimidazolin-2-ylidene (1b) and 1,3-diisopropyl-4,5-dimethylimidazolin-2-
ylidene (1c) with trimethylsilyl azide in boiling toluene furnishes the corresponding 2-
(trimethylsilylimino)imidazolines 2a – c. Treatment of Re2O7 with a twofold excess of these
N-silylated imines results in the formation of the imidazolin-2-iminato trioxorhenium(VII) com-
plexes 3a – c and hexamethyldisiloxane, Me3SiOSiMe3. The molecular structures of 2a, 3a and
3b are reported. In addition, the X-ray crystal structure determination of complex 3c · H2O is
presented, which has formed by hydrolysis and cleavage of the metal-nitrogen bond in 3c. 3c ·
H2O consists of 2-aminoimidazolium cations and tetraoxorhenate(VII) anions, which are linked by
N–H –O hydrogen bonds.
Key words: Carbenes, Imidazolin-2-ylidenes, Imido Ligands, Imidazolin-2-iminato Complexes,
Rhenium
Introduction
Initiated by Hubert Schmidbaur in the mid 1960ies
[1, 2], the organometallicchemistry of phosphoraneim-
inato ligands, R3PN−, has developed into a broad area
of research which has produced a large number of
structurally diverse main group element and transition
metal complexes [3]. Due to their capability to act as
2σ,4π-electron donors, these anionic ligands can be
regarded as monodentate analogues to cyclopentadi-
enyls, C5R5, and this relationship has been described
as a pseudo-isolobal phenomenon (Fig. 1) [4]. Accord-
ingly, the use of phosphoraneiminato instead of the tra-
ditional cyclopentadienyl ancillary ligands could pro-
duce complexes of modified and potentially enhanced
catalytic activity. This concept was proved successful
by the synthesis of extremely active titanium catalysts
for olefin polymerization [5].
Fig. 1. Isolobal relationship between phosporaneiminato,
imidazolin-2-iminato and cyclopentadienyl complexes; me-
someric structures for imidazolin-2-iminato ligands.
replacement of phosphane by N-heterocyclic carbene
ligands has created transition metal complexes with
improved stability and significantly enhanced cat-
alytic activity. Similarly, substitution of the R3P for
an imidazolin-2-ylidene moiety in phosphoraneimides
gives imidazolin-2-imides of type I, which can be de-
scribed by the two limiting mesomeric structures IA
and IB (Fig. 1). The ability of an imidazolium ring to
stabilize a positive charge in a more effective manner
than a phosphonium group should increase the neg-
ative charge on the nitrogen atom and thus lead to
Another concept, which has been extremely use-
ful for boosting the performance of numerous transi-
tion metal catalysts, is based on the striking similar-
ity between electron-rich organophosphanes and nu-
cleophilic carbenes of the imidazolin-2-ylidene type
in terms of their ligand properties [6]. In many cases,
c
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M. Tamm et al. · Trioxorhenium(VII) Complexes with Imidazolin-2-iminato Ligands
the formation of ligands with enhanced basicity and
electron donating capacity. However, only a surpris-
ingly small number of publications has been devoted
to the preparation of imidazolin-2-iminato transition
metal complexes [7], and these reports have been con-
fined to the use of the ligand precursor 2-imino-1,3-
dimethylimidazoline [8].
Recently [9], we have presented a novel method
for the preparation of imidazolin-2-iminato ligands,
which is based on our observation that the stable
carbene 1,3-di-tert-butylimidazolin-2-ylidene (1a) un-
dergoes a Staudinger reaction [10] upon treatment
with trimethylsilyl azide to furnish the N-silylated 2-
Fig. 2. ORTEP drawing of 2a with displacement ellip-
soids drawn at 50% probability. Selected bond lengths
◦
˚
[A] and angles [ ]: C1−N1 1.275(3), N1−Si 1.655(2),
C1−N2 1.394(2), C1−N3 1.393(3), N2−C2 1.387(3),
iminoimidazoline 2a in a similar way as described N3−C3 1.387(3), C2−C3 1.326(4); C1−N1−Si 169.3(2),
N2−C1−N3 104.5(2) [11].
for the preparation of silylated phosphoraneimines
(Scheme 1) [2, 3c]. With this contribution, we would
like to demonstrate that this reaction is indeed gener-
ally applicable to different carbenes of the imidazolin-
2-ylidene type. In addition, the use of the resulting 2-
iminoimidazolines for the preparation of high-valent
imidazolin-2-iminatotrioxorhenium(VII) complexes is
reported.
benes 1,3-di-tert-butylimidazolin-2-ylidene (1a) and
1,3-dimesitylimidazolin-2-ylidene (1b) can be easily
followed by 1H NMR spectroscopy as pronounced
high-field shifts of −0.74 (1a) and −0.72 ppm (1b)
are observed for the resonances of the NCH hydrogen
atoms upon formation of the imines 2a and 2b. For the
conversion of 1,3-diisopropyl-4,5-dimethylimidazolin-
2-ylidene (1c) into the corresponding imine 2c on
the other hand, a marked low-field shift of the septet
Results and Discussion
Synthesis of N-silylated 2-iminoimidazolines
CH resonance from 3.95 ppm to 4.61 ppm is indica-
tive of product formation. According to their 1H and
The reaction of the imidazolin-2-ylidenes 1a – c
with trimethylsilyl azide in boiling toluene for 72 h
13C NMR spectra, the imines 2 exhibit pseudo-C2v
symmetry in solution implying that rotation around the
N1-C1 axis is fast on the NMR time scale.
furnishes the 2-(trimethylsilylimino)imidazolines 2a –
c in excellent yield (Scheme 1). Recrystallization from
hexane affords 2a and 2b as colourless crystals. 2c
is isolated as a brownish oil, which can be purified
by bulb-to-bulb distillation. The conversion of the car-
Crystals of 2a were subjected to an X-ray diffraction
analysis, and the molecular structure of 2a is shown in
Fig. 2 [9, 11]. The exocyclic C1−N1 bond distance of
˚
1.275(3) A is shorter than the corresponding distance
˚
in 2-imino-1,3-dimethylimidazoline [1.296(2) A] [8]
despite the steric bulk of the tert-butyl and trimethylsi-
lyl substituents. The C1−N1−Si angle of 169.3(2)◦
in 2a is close to linearity and thereby significantly
larger than the corresponding P−N−Si angles in
silylated iminophosphoranes such as Ph3PNSiMe3
[140.2(2)◦] [12], (C6H11)3PNSiMe3 [149.8(2)◦] [13]
and (Me2N)3PNSiMe3 [160.0(2)◦] [14]. This
observation follows the accepted electron donor
trend [15], which is expected to increase in the order
PPh3 < P(C6H11)3 < P(NMe2)3 < 1. For
a more
detailed structural comparison, however, not only the
electronic influence of the carbene and phosphane
substituents but also their steric bulk as well as
molecule packing forces must be taken into account
(vide infra).
Scheme 1.
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M. Tamm et al. · Trioxorhenium(VII) Complexes with Imidazolin-2-iminato Ligands
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Table 1. Re–O stretching frequencies (cm−1) for L-ReO3
complexes (L = imidazolin-2-imide or phosphoraneimide)a.
Synthesis of imidazolin-2-iminatotrioxorhenium(VII)
complexes
Compound
νs (A1)
928
949
929
950
ν
as (E)
907
917
903
921
917
In a similar fashion as described by M. Schmidt
and H. Schmidbaur [16] for the synthesis of
[Me3SiOReO3] from Re2O7 and Me3SiOSiMe3 and as
described by H. W. Roesky [17] and K. Dehnicke [18]
for the syntheses of phosphoraneiminatorhenium com-
plexes, [(R3PN)ReO3] (R = Ph, Et), from R3PNSiMe3,
treatment of rhenium(VII) oxide with a twofold excess
of the silylated 2-iminoimidazolines 2 in THF leads to
the clean formation of the imidazolin-2-iminato com-
plexes 3a – c, which can be isolated as yellow-orange
crystals in good yield (Scheme 1). Desilylation of 2a
and 2b and formation of 3a and 3b results in a pro-
nounced down-field shift (∆δ ≈ +1.40 ppm) of the
resonances observed for the NHC hydrogen atoms in-
dicating a strong electron release towards the metal
atom. To assess the electron donating ability of the
imidazolin-2-iminato ligands, the IR spectra of 3a – c
were measured in Nujol, and these results are sum-
marized in Table 1. As expected for local C3v sym-
metry at the metal atom, each complex exhibits two
IR absorptions, which can be assigned to the symmet-
ric and asymmetric Re–O stretching vibrations, respec-
tively [19]. Comparison with the stretching frequencies
reported for [(R3PN)ReO3] (R = Ph, Et) [18] (Table 1)
reveals that the N,N’-dialkylimidazolin-2-iminato lig-
ands in 3a and 3c are stronger electron donors or,
in other words, exhibit a stronger π-electron release
capability than the phosphoraneimides R3PN− (R =
Ph, Et), which results in a more pronounced weaken-
ing of the Re–O bonds and the observation of lower
wavenumbers. In contrast, the N,N’-diarylimidazolin-
2-iminato ligand in 3b appears to have similar or even
poorer donor properties than the triethyl derivative
Et3PN−, but it can still be regarded as a slightly better
electron donor than the triphenyl derivative Ph3PN−.
It should also be noted that the corresponding Re–
O absorptions of related cyclopentadienyl complexes
[(η-C5R5)ReO3] (R = H, Me) are observed at sig-
3a
3b
3c
[(Ph3PN)ReO3]b
[(Et3PN)ReO3]b
a
944
In Nujol; b taken from reference [18].
metal atom. The Re–O bond lengths in 3a [1.698(5)–
1.733(6) A] and 3b [1.700(5)– 1.715(4) A] fall in the
˚
˚
expected ranges and are in good agreement with those
˚
observed in [(Ph3PN)ReO3] [1.691(7)– 1.710(8) A]
˚
and [(Et3PN)ReO3] [1.701(4)– 1.714(3) A] [18] as
well as with those found for the analogous cy-
clopentadienyl complex [(η-C5H5)ReO3] [1.693(4)–
˚
1.711(4) A] [20]. Surprisingly, both structures differ
significantly with respect to the coordination and ori-
entation of the imidazolin-2-iminato ligands. Whereas
an almost linear Re−N1−C1 arrangement is ob-
served for the di-tert-butylimidazolin-2-iminato lig-
and in 3a [172.0(5) and 172.0(6)◦ for two crystal-
lographically independent molecules], its dimesityl
substituted counterpart in 3b exhibits a consider-
ably smaller Re−N1−C1 angle of 150.1(4)◦. Thereby,
the imidazolin-2-iminato ligand bends away from the
O1 oxygen atom and adopts a staggered conforma-
tion, in which the plane containing the imidazoline
ring, N1 and Re is bisecting the O2−Re−O3 plane
(Fig. 4). As expected, the considerably stronger bend-
ing of the ligand in 3b produces a longer Re−N1
˚
distance in comparison with 3a [1.805(4) A versus
˚
1.792(6) and 1.747(7) A]; a clear trend, however, can
not be derived due to the observation of two dis-
tinctly different Re−N1 distances for the two indepen-
˚
dent molecules in 3a. With 1.793(7) and 1.786(4) A,
the Re−N bond lengths in [(R3PN)ReO3] (R = Ph,
Et) fall in the same range, whereas the values of
the corresponding Re−N−P angles [162.0(5) and
160.6(2)◦] are intermediate between those found for
3a and 3b. The strong variation of the Re−N−C
and Re−N−P angles, respectively, is not surprising
in view of quantum chemical calculations, which re-
veal that the potential energy surface of the model
complex [(H3PN)ReO3] is extremely shallow with
respect to the Re−N−P angle [4]. Therefore, this
geometric parameter is highly responsive to struc-
tural changes of the ligand substitution pattern and
should also be easily affected by molecule packing
forces.
nificantly lower wavenumbers (νs = 925 − 915 cm−1
,
ν
as = 895−880 cm−1) [19].
Recrystallization of 3a and 3b from acetonitrile af-
forded single crystals suitable for structure determi-
nation by X-ray diffraction; the molecular structures
of 3a and 3b are shown in Fig. 3 and 4, respec-
tively. In both complexes, the angles about the rhe-
nium atom are in agreement with a slightly distorted
tetrahedral environment with local C3v symmetry at the
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M. Tamm et al. · Trioxorhenium(VII) Complexes with Imidazolin-2-iminato Ligands
changes on the structural properties of imidazolin-
2-iminato complexes. Unfortunately, several attempts
to obtain single crystals of 3c have repeatedly lead
to the isolation of a crystalline hydrolysis product,
in which the metal-nitrogen bond in 3c is cleaved
with one water molecule to give the corresponding
2-aminoimidazolium tetraoxorhenate(VII) 3c · H2O
(Scheme 1). In the solid state, 3c · H2O forms
an extended structure, in which the amino group of
each imidazolium cation is involved in N−H−O hy-
drogen bonding to two perrhenate anions. As each
ReO4 anion is also linking two countercations via an
NH−O−Re−O−HN arrangement, a polymeric zigzag
chain is formed, a part of which is shown in Fig. 5.
Fig. 3. ORTEP drawing 3a (molecule A) with displace-
ment ellipsoids drawn at 50% probability. Molecules A und
B differ in the orientation of the ReO3 moiety with re-
All structural parameters fall in the expected ranges
and are in good agreement with the values obtained
by X-ray structure determination of other salts con-
taining either 2-aminoimidazolium [7b, 21] or tetraox-
orhenate(VII) ions involved in hydrogen bonding [22].
˚
spect to the imidazoline ring. Selected bond lengths [A]
and bond angles [◦] for molecule A [molecule B]: Re−Ol
1.718(5) [1.698(5)], Re−O2 1.705(4) [1.703(5)], Re−O3
1.733(6) [1.727(6)], Re−N1 1.792(6) [1.747(7)], N1−C1
1.315(8) [1.348(10)], C1−N2 1.345(9) [1.358(8)], C1−N3
1.348(9) [1.382(8)], N2−C2 1.386(10) [1.381(10)], N3−C3
1.394(10) [1.378(10)], C2−C3 1.339(12) [1.324(12)];
N2−C1−N3 108.2(6) [107.4(6)], Re−N1−C1 172.0(5)
[172.0(6)], N1−Re−O1 109.4(3) [110.2(3)], N1−Re−O2
110.2(3) [110.4(3)], N1−Re−O3 109.0(3) [108.7(3)],
O1−Re−O2 110.0(2) [108.8(2)], O1−Re−O3 109.0(3)
[109.5(3)], O2−Re−O3 109.1(3) [109.2(3)].
Conclusion
With this contribution, we have demonstrated
that the Staudinger reaction between various sta-
ble carbenes of the imidazolin-2-ylidene type and
trimethylsilyl azide gives access to N-silylated 2-
iminoimidazolines, which can be used directly for the
preparation of imidazolin-2-iminato transition metal
complexes from metal halides or oxides with cleav-
age of the N−Si bond and concomitant formation
of trimethylsilyl halides or hexamethyldisiloxane, re-
spectively. These imidazolin-2-imides represent a suit-
able addition to well-established phosphoraneimides
and are a novel class of promising ancillary ligands
for the design and preparation of homogeneous cat-
alysts. The trioxorhenium(VII) complexes presented
here are structurally remarkably different indicating
that the electronic and steric features of these ligands as
well as the properties of the resulting transition metal
complexes can be easily varied. As trioxorhenium(VII)
complexes of the general type [LReO3] are particu-
larly useful for applications in homogeneous oxidation
catalysis [19], the reactivity and catalytic activity of the
corresponding imidazolin-2-iminato complexes 3 will
be further investigated.
Fig. 4. ORTEP drawing of 3b with displacement ellip-
˚
soids drawn at 50% probability. Selected bond lengths [A]
and bond angles [◦]: Re−Ol 1.700(5), Re−O2 1.715(4),
Re−O3 1.712(5), Re−N1 1.805(4), N1−C1 1.309(7),
C1−N2 1.358(7), C1−N3 1.353(6), N2−C2 1.396(7),
N3−C3 1.396(7), C2−C3 1.341(13); N2−C1−N3 106.9(4),
Re−N1−C1 150.1(4), N1−Re−O1 108.0(2), N1−Re−O2
112.9(2), N1−Re−O3 111.1(2), O1−Re−O2 107.9(2),
O1−Re−O3 108.8(2), O2−Re−O3 108.0(3).
Experimental Section
All operations were performed in an atmosphere of dry
argon by using Schlenk and vacuum techniques. All solvents
The structural characterization of 3c would have
allowed to further investigate the impact of such were purified by standard methods and distilled prior to use.
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M. Tamm et al. · Trioxorhenium(VII) Complexes with Imidazolin-2-iminato Ligands
1501
Fig. 5. DIAMOND drawing of the extended solid state structure of 3c · H2O with displacement ellipsoids drawn at
50% probability. The hydrogen atoms are omitted for clarity, except for those involved in N-H-O hydrogen-bonding. Se-
◦
˚
lected bond lengths [A] and bond angles [ ]: Re−Ol 1.705(3), Re−O2 1.703(4), Re−O3 1.687(4), Re−O4 1.706(3),
N1−C1 1.332(5), C1−N2 1.344(4), C1−N3 1.342(4), N2−C2 1.405(4), N3−C3 1.403(5), C2−C3 1.342(4); N2−C1−N3
108.6(3), O1−Re−O2 109.92(18), O1−Re−O3 109.7(2), O1−Re−O4 109.11(14), O2−Re−O3 108.6(2), O2−Re−O4
i
109.46(19), O3−Re−O4 110.0(2). Hydrogen bonds: N1−H1 0.85(4), N1−H2 0.77(4), H1···O1 2.06(4), H2···O2 2.12(4);
N1−H1···O1i 174(4), N1−H2···O2 170(4); i: 1−x, 0.5−y, −0.5+z.
The imidazolin-2-ylidenes 1a [23], 1b [24], and 1c [25] were 113.9 (NCMe), 45.0 (NCH), 21.3 (NCHCH3), 10.0
prepared according to published procedures. Trimethylsilyl (NCCH3), 4.3 (SiCH3). – C14H29N3Si (267.48): calcd.
azide was received from Aldrich and dried over molecular C 62.86, H 10.93, N 15.71; found C 62.55, H 11.10, N 15.34.
˚
sieve (4 A).
General procedure for the preparation of imidazolin-2-
General procedure for the preparation of 2-(trimethylsilyl- iminatotrioxorhenium(VII) complexes (3)
imino)imidazolines (2)
The imine 2 (0.5 mmol) and Re2O7 (0.25 mmol) were dis-
A solution of the imidazolin-2-ylidene 1 (10 mmol) in solved in THF (15 ml), and the resulting reaction mixture was
toluene (20 ml) was treated dropwise with trimethylsilyl stirred at ambient temperature for 24 h. The resulting precip-
azide (24 mmol) at ambient temperature, and the resulting itate was isolated by filtration, washed with THF and dried in
reaction mixture was subsequently heated in boiling toluene vacuo. The rhenium complexes were obtained as crystalline
for 72 h. Filtration and evaporation of the solvent afforded yellow (3a and 3b) or orange solids (3c), respectively.
3a: Yield: 78%. 1H NMR (400 MHz, DMSO-d6): δ =
the imines as yellowish solids (2a and 2b) or as a brownish
1
7.40 (s, 2 H, NCH), 1.54 (s, 18 H, CCH3). – 13C { H} NMR
oil (2c), respectively, which can be purified by bulb-to-bulb
distillation at 180 ◦C/9 mbar.
(100.52 MHz, DMSO-d6): δ = 125.6 (NCN), 114.6 (NCH),
2a: Yield: 88%. 1H NMR (400 MHz, C6D6): δ = 6.03 (s, 59.1 (NCCH3), 28.4 (CCH3). – IR (Nujol): ν = 928, 907
2 H, NCH), 1.36 (s, 18 H, CCH3), 0.52 (s, 9 H, SiCH3). – (Re–O) cm−1. – C11H20N3O3Re (428.50): calcd. C 30.83,
1
13C { H} NMR (100.52 MHz, C6D6): δ = 139.7 (NCN), H 4.70, N 9.81; found C 30.82, H 4.34, N 9.73.
3b: Yield: 85%. 1H NMR (270 MHz, CD3CN): δ = 7.16
107.5 (NCH), 54.2 (NCCH3), 28.1 (CCH3), 4.4 (SiCH3). –
C14H29N3Si (267.48): calcd. C 62.86, H 10.93, N 15.71;
found C 62.63, H 11.09, N 15.57.
(s, 2 H, NCH), 7.10 (s, 4 H, m-CH), 2.35 (s, 6 H, p-CH3),
2.11 (s, 12 H, o-CH3). – 13C { H} NMR (100.52 MHz,
1
2b: Yield: 80%. 1H NMR (400 MHz, C6D6): δ = 6.78 CD3CN): δ = 140.8 (ipso-C), 136.0 (o-CMe), 135.2 (NCN),
(s, 4 H, m-CH), 5.76 (s, 2 H, NCH), 2.21 (s, 12 H, o- 129.4 (m-CH), 119.9 (p-CMe), 118.6 (NCH), 20.2 (p-CH3),
CH3), 2.10 (s, 6 H, p-CH3), −0.09 (s, 9 H, SiCH3). – 16.7 (o-CH3). – IR (Nujol): ν = 949, 917 (Re–O) cm−1
.
13C { H} NMR (100.52 MHz, C6D6): δ = 140.7 (NCN), C21H24N3O3Re (552.64): calcd. C 45.64, H 4.38, N 7.60;
1
137.6 (ipso-C), 136.9 (o-CMe), 134.5 (p-CMe), 128.9 found C 44.79, H 3.87, N 7.14.
3c: Yield 78%. 1H NMR (270 MHz, C6D6): δ = 4.07
(m-CH), 112.1 (NCH), 20.8 (p-CH3), 18.0 (o-CH3), 3.1
(SiCH3). – C24H31N3Si (391.63): calcd. C 73.61, H 8.49,
N 10.73; found C 72.55, H 8.16, N 10.58.
(sept, 2 H, NCHMe), 1.21 (s, 6 H, NCCH3), 1.03 (d, 12 H,
CHCH3). – 13C { H} NMR (100.52 MHz, C6D6): δ = 119.3
1
2c: Yield: 92%. 1H NMR (400 MHz, C6D6): δ = (NCMe), 48.4 (NCH), 20.5 (NCHCH3), 8.6 (NCCH3); the
4.59 (sept, 2 H, NCHMe), 1.71 (s, 6 H, NCCH3), NCN resonance could not be detected. – IR (Nujol): ν =
1.18 (d, 12 H, CHCH3), 0.44 (s, 9 H, SiCH3). – 929, 903 (Re–O) cm−1. – C11H20N3O3Re (428.50): calcd.
13C { H} NMR (100.52 MHz, C6D6): δ = 144.4 (NCN), C 30.83, H 4.70, N 9.81; found C 29.84, H 4.82, N 9.24.
1
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M. Tamm et al. · Trioxorhenium(VII) Complexes with Imidazolin-2-iminato Ligands
Table 2. Summary of the crys-
3a
3b
3c · H2O
C11H22N3O4Re
446.53
tal data and details of data col-
lection and refinement for com-
pounds 3a, 3b, and 3c · H2O.
Empirical formula
Formula mass
Crystal system
Space group
C11H20N3O3Re
428.51
C21H24N3O3Re
552.64
orthorhombic
Pca21 (no. 29)
12.7656(1)
18.0375(1)
12.1492(1)
90
monoclinic
P21 (no. 4)
7.2895(2)
16.2043(4)
8.8157(2)
93.0229(8)
1039.87(5)
2
monoclinic
P21/n (no. 14)
7.5630(1)
14.3826(2)
14.2043(2)
101.4357(5)
1514.41(4)
4
˚
a [A]
˚
b [A]
˚
c [A]
β [◦]
3
˚
V [A ]
2797.47(4)
8
Z
ρcalcd [g cm−3
]
2.035
8.692
123
1.765
5.869
123
1.959
8.037
293
µ [mm−1
T [K]
]
F(000)
1648
540
864
Crystal size [mm]
0.56×0.25×0.05
1.13/25.37
h : 15
0.41×0.18×0.08
0.46×0.25×0.20
θ-Range [◦]
2.31/25.43
2.03/25.33
Index ranges
h :
8
h :
9
k : 21
l : 14
61483
k : 19
l : 10
20674
k : 17
l : 17
37653
Reflections collected
Independent reflections
[Io > 2σ(Io)/all data/Rint
Data / restraints / parameters
R1[Io > 2σ(Io)/all data]
wR2[Io > 2σ(Io)/all data]
GOF
]
4750/4946/0.078
4946/1/338
0.0274/0.0291
0.0736/0.0747
1.092
3628/3801/0.070
3801/1/259
0.0242/0.0263
0.0607/0.0619
1.075
2595/2776/0.046
2776/0/261
0.0192/0.0213
0.0399/0.0408
1.079
Weights a/b
∆ρmax/min [e·A
0.0533/3.6191
1.73/-1.48
0.0345/1.4980
1.39/-1.11
0.0083/3.4361
0.73/-0.88
−3
˚
]
Single crystal X-ray structure determination of compounds nation of direct methods and difference Fourier syntheses.
3a, 3b, and 3c · H2O
All non-hydrogen atoms were refined with anisotropic dis-
placement parameters. For 3a and 3b, all hydrogen atom
positions were calculated in ideal positions (riding model).
3a (3b, 3c · H2O): Crystal data and details of the structure
determination are presented in Table 2. Suitable single crys- For 3c · H2O, all hydrogen atom positions were found in
tals for the X-ray diffraction study were grown from CH3CN the difference map calculated from the model containing
all non-hydrogen atoms, and the hydrogen positions were
(CH3CN, CH3CN). A clear yellow fragment (yellow plate,
colorless prism) was stored under perfluorinated ether, trans- refined with individual isotropic displacement parameters.
ferred in a Lindemann capillary, fixed, and sealed. Prelimi- Full-matrix least-squares refinements with 338 (259, 261)
parameters were carried out by minimizing Σw(F 2 − Fc2)2
nary examination and data collection were carried out on an
o
area detecting system (NONIUS, MACH3, κ−CCD) at the with the SHELXL-97 weighting scheme and stopped at
window of a rotating anode (NONIUS, FR951) and graphite shift/err<0.001. The final residual electron density maps
˚
showed no remarkable features. Neutral atom scattering fac-
monochromated Mo-Kα radiation (λ = 0.71073 A). The unit
cell parameters were obtained by full-matrix least-squares re- tors for all atoms and anomalous dispersion corrections for
finement of 2930 (1985, 2907) reflections. Data collection the non-hydrogen atoms were taken from International Ta-
bles for Crystallography. All calculations were performed on
were performed at 123 (123, 293) K (OXFORD CRYOSYS-
TEMS) within a θ-range of 1.13◦ < θ < 25.37◦ (2.31◦ < an Intel Pentium II PC, with the STRUX-V system, includ-
θ < 25.43◦, 2.03◦ < θ < 25.33◦). Measured each with nine ing the programs PLATON, SIR92, and SHELXL-97 [26].
data sets in rotation scan modus with ∆ϕ/∆ω = 1.0◦ (1.0◦, 3a: As shown by Flack’s parameter the crystal is twinned.
2.0◦). A total number of 61483 (20674, 37653) intensities [TWIN / BASF = 0.453(11)]. The asymmetric unit cell con-
were integrated. Raw data were corrected for Lorentz, po- tains two crystallographically independent molecules A and
larization, and, arising from the scaling procedure, for latent B, which differ in the orientation of the ReO3 moiety with
decay and absorption effects. After merging [Rint = 0.078 respect to the imidazolin ring. 3b: The correct enantiomer
(0.070, 0.046)] a sum of 4946 (3801, 2776) (all data) and is proved by Flack’s parameter ε = −0.004(11). 3c · H2O:
4750 (3628, 2595) [I > 2σ(I)], respectively, remained and Small extinction effects were corrected with the SHELXL-97
all data were used. The structure was solved by a combi- procedure [ε = 0.00130(9)].
Unauthenticated
Download Date | 5/19/16 4:41 PM

M. Tamm et al. · Trioxorhenium(VII) Complexes with Imidazolin-2-iminato Ligands
1503
Acknowledgements
6-1). M. T. is grateful to Prof. W. A. Herrmann (Munich) for
the appointment to temporarily represent the Chair of In-
organic Chemistry at the Technische Universita¨t Mu¨nchen.
S. B. thanks the GE foundation for an Edison award 2004.
The continuation of this work will be financially sup-
ported by the Deutsche Forschungsgemeinschaft (Ta 189/
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Unauthenticated
Download Date | 5/19/16 4:41 PM

1504
M. Tamm et al. · Trioxorhenium(VII) Complexes with Imidazolin-2-iminato Ligands
System to Handle X-Ray Data, TU Mu¨nchen, Garch-
structure factors) for the structures reported in this
paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary
publication nos. CCDC-246961 (3a), CCDC-246962
(3b), and CCDC-246963 ( 3c · H2O). Copies of the
data can be obtained free of charge on application
to The director, CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK [fax: (+44)1223-336-033; e-mail:
fileserv@cccdc.cam.ac.uk].
ing, Germany (1997); e) A. L. Spek, PLATON: A
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Germany (1998); h) Crystallographic data (excluding
Unauthenticated
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