P. Traar et al. / Journal of Molecular Catalysis A: Chemical 385 (2014) 54–60
59
Repeated addiꢀon of cyclooctene
100
90
80
70
60
50
40
30
20
10
0
3a
3b
1st run
2nd run
3rd run
catalyꢀc cycles
Fig. 6. Repeated addition of cyclooctene and TBHP to catalysts 3a and 3b. Conditions used were 0.05 mol% catalyst, 2 equiv. TBHP in DCE at 80 ◦C.
similar catalytic activities. In contrast, the related chiral complex
[MoO2(oz*)2] displayed a rather sluggish behavior as epoxidation
catalyst, albeit under different conditions than reported here [24].
Complex [MoO2(ozMe2)2] was tested in the epoxidation of styrene
at room temperature, but showed no activity at all [37].
Chemistry. Deviations from calculated elemental compositions are
due to residual solvent in the sample.
4.2. Single crystal X-ray diffraction analyses
All the measurements were performed using graphite-
monochromatized
Mo
K␣
radiation
at
100 K.
3a:
3. Conclusions
C26H20MoN2O6, Mr 552.38, triclinic, space group P-1,
◦
˚
˚
˚
a = 7.2205(3) A, b = 11.0269(4) A, c = 13.9798(5) A, ˛ = 86.8539(14) ,
ˇ = 80.1179(13)◦,
ꢃ = 76.5620(12)◦,
V = 1066.40(7) A ,
Z = 2,
3
˚
Within this paper we present the synthesis and characterization
of two new dioxomolybdenum(VI) complexes 3a-b equipped with
the bidentate monoanionic naphtholate-oxazoline ligands 2a-b. All
analytical data is consistent with the formation of asymmetrically
disubstituted complexes. Complexes 3a-b were also characterized
by single crystal X-ray diffraction analysis. In the case of 3b, both
the O,O-isomer (3b) as well as the N,N-isomer (3b’) could be char-
acterized, although 3b’ was only formed in traces. Furthermore
complexes 3a-b were tested in the catalytic epoxidation of various
olefinic substrates. In all cases they showed good to high activity
with acceptable selectivities comparable or higher to other pub-
lished dioxomolybdenum(VI) complexes.
dcalc = 1.720 g cm−3
,
ꢄ = 0.665 mm−1
.
A
total of 14358 reflec-
tions were collected (ꢅmax = 30.0◦), from which 6212 were unique
(Rint = 0.0253), with 5671 having I > 2ꢆ(I). For 322 parameters
final R indices of R1 = 0.0263 and wR2 = 0.0669 (GOF = 1.041) were
obtained. 3b: C30H28MoN2O6, Mr 608.48, monoclinic, space group
˚
˚
˚
P 2/n, a = 15.890(3) A, b = 10.632(2) A, c = 16.039(3) A, ˇ = 96.191(8)(,
V = 2693.9(9) A3, Z = 4, dcalc = 1.500 g cm−3, ꢄ = 0.534 mm−1. A total
˚
of 10725 reflections were collected (ꢅmax = 26.0◦), from which
5256 were unique (Rint = 0.0717), with 3092 having I > 2ꢆ(I). For
363 parameters final R indices of R1 = 0.0855 and wR2 = 0.2388
(GOF = 1.081) were obtained. 3b’: C30H28MoN2O6, Mr 608.48,
˚
˚
orthorhombic, space group P b c n, a = 17.4070(6) A, b = 7.6439(3) A,
c = 19.8304(7) A, V = 2638.58(17) A , Z = 4, dcalc = 1.532 g cm−3
,
3
˚
˚
4. Experimental
ꢄ = 0.545 mm−1
. A total of 27367 reflections were collected
(ꢅmax = 30.0◦), from which 3851 were unique (Rint = 0.0353),
with 2990 having I > 2ꢆ(I). For 183 parameters final R indices
of R1 = 0.0244 and wR2 = 0.0659 (GOF = 1.060) were obtained.
For full details on data collection and refinement please refer
to the Supporting Information. Crystallographic data (excluding
structure factors) for the structure of 3a, 3b and 3b’ reported in this
paper have been deposited with the Cambridge Crystallographic
Data Center as supplementary publication no. CCDC-940630 (3a),
CCDC-945467 (3b) and CCDC-945466 (3b’). Copies of the data
can be obtained free of charge on application to: The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: (int.) +44
1223/336 033; E-mail: deposit@ccdc.cam.ac.uk]. A summary of the
crystallographic data can be found in the Supporting Information
which is available online free of charge.
Synthesis of 2a: a suspension of 1a (2.31 g, 10 mmol, 1 equiv.)
in dichloromethane (50 mL) was cooled to 0 ◦C. Thionyl chloride
(1.79 g, 15 mmol, 1.5 equiv.) was added under Ar slowly over a
period of 15 min resulting in a brown solution. The solution was
allowed to slowly warm up to room temperature over night. After
12 h stirring at room temperature a suspension was obtained con-
taining crude 2a·HCl as an off-white solid. The off-white solid was
4.1. General remarks
Unless otherwise specified, all experiments were performed
under atmospheric conditions with standard laboratory equipment
at the Institute of Chemistry, University of Graz. For the synthesis of
1a-b please refer to the Supporting Information. All other chemicals
and solvents were purchased from commercial sources and used
as received. 1H and 13C NMR spectra were recorded on a Bruker
Optics Instrument. Chemical shifts are reported in parts per million
(ppm) and referenced to residual protons or carbons in the deuter-
ated solvent. Electron impact mass spectroscopy measurements
(EI-MS) were recorded with an Agilent 5973 MSD mass spectrom-
eter with Direct Probe. Gas chromatography mass spectroscopy
measurements (GC–MS) have been performed with an Agilent
7890 A (column type Agilent 19091J-433), coupled to a mass spec-
trometer type Agilent 5975 C. Samples for infrared spectroscopy
were measured on a Bruker Optics ALPHA ATR FT-IR Spectrome-
ter. IR bands are reported with wave number (cm−1). Elemental
analyses were measured on a Heraeus Vario Elementar automatic
analyzer at the Graz University of Technology, Institute of Inorganic