Full Papers
the reaction mixture had been stirring for 30 min, dmen (30 mL,
Conclusions
0
.276 mmol) was added, which led to a color change from green
to brown. Immediately, a freshly prepared 0.5m solution of
In summary, we have developed a new and efficient protocol
for the preparation of structurally diverse anilines by reduction
of the corresponding nitro or azo compounds. For both sub-
strates, the reactions proceed easily under mild conditions
HBF ·ether complex (0.66 mL, 0.3306 mmol) in CH CN was added
4
3
and the solution turned green. The reaction mixture was stirred at
room temperature for 30 min. After filtration, the green solution
was concentrated under reduced pressure and the desired product
was precipitated by adding diethyl ether (50 mL). Finally, the green
solid was separated by filtration and washed with a cold mixture
of hexane/toluene (1:1, 30 mL), boiling hexane (30 mL), cold iso-
propanol (10 mL), and diethyl ether to yield an air-stable product
that was characterized as [Mo S Cl (dmen) ]BF (54 mg, 75% yield).
(
room temperature or T=808C, ambient pressure) with silanes
as the reducing agents. This catalytic protocol shows good
functional-group tolerance towards other easily reducible moi-
eties, such as vinyl, acetyl, cyanide, or ester groups. As the cat-
alyst, a well-defined Mo S complex bearing diamine ligands
3
4
3
3
4
3
4
Elemental analysis: calcd (%) for Mo Cl S N C H BF : C 16.50, H
3
3
4
6
12 36
1
4
has been employed. The preparation of this novel catalyst,
4
3
(
.15, N 9.62; found: C 16.57, H 4.30, N 9.58; H NMR: d=2.20 (br,
=5.6 Hz), 3.04 (m, 6H, CH ), 3.61
m, 3H, CH ), 3.85 (d, 3H, CH ; 9H, CH , J
(br, 3H, NH); C { H} NMR: d=44.22 (s, CH ), 50.48 (s, CH ), 52.42
3 3
(s, CH ), 57.77 ppm (s, CH ); ESIMS (CH CN, 20 V): m/z: 786.9 [M ].
2 2 3
namely [Mo S Cl (dmen) ](BF ) (dmen: N,N’-dimethylethylenedi-
2
3
4
3
3
4
H, NH), 2.78 (d, 9H, CH , J
3
HÀH(N)
2
amine), has been carried out by the unprecedented coordina-
tion of diamine ligands to the Mo S cluster core in a one-pot
2
=5.9 Hz), 6.34 ppm
2
2
3
HÀH(N)
13
1
3
4
2
À
+
two-step procedure from the readily available [Mo S Cl ] dia-
3
7
4
nion. The molecular structure of this complex has been deter-
mined by multinuclear NMR spectroscopy, electrospray-ioniza-
tion mass spectrometry, and single-crystal X-ray crystallogra-
phy.
X-ray data collection and structure refinement
Suitable crystals for X-ray studies of the [Mo S Cl (dmen) ]BF salt
3
4
3
3
4
were grown by slow evaporation of a sample solution in dichloro-
methane:diethyl ether (1:1). X-ray diffraction experiments were car-
ried out on a Agilent Supernova diffractometer equipped with an
Atlas CCD detector by using CuKa radiation (l=1.54184 ). No in-
strument or crystal instabilities were observed during data collec-
Experimental Section
General remarks
[21]
tion.
Absorption corrections based on the multiscan method
All reactions were performed under a nitrogen atmosphere with
standard Schlenck techniques. The molecular complex
[22]
were applied. The structures were solved by direct methods in
SHELXS-97 and refined by the full-matrix method on the basis of F
2
(
nBu N) [Mo S Cl ] was prepared according to the literature pro-
4 2 3 7 6
[11d]
with the program SHELXL-97 by using the OLEX software pack-
cedure.
[23]
age. Graphics were performed with the Diamond visual crystal
[24]
structure information system software.
Crystal data for
[
Mo S Cl (dmen) ](BF )·0.5CH Cl : C H BCl F Mo N S ; M=916.15;
3
4
3
3
4
2
2
12.5 37
4
4
3
6 4
Physical measurements
orthorhombic; space group Pccn; a=21.9457(3), b=17.55239(19),
c=16.2584(2) ; a=90, b=90, g=908; V=6262.71(13) ; T=
200.00(14) K; Z=8; m(Cu )=15.694 mm ; reflections collected/
unique=26562/5581 (Rint =0.0548); final refinement converged
with R =0.0514 and R =0.1295 for all reflections; goodness of
fit=1.148;
À0.665 e .
The structure was refined in the orthorhombic Pccn space group.
The non-hydrogen atoms of the cluster and the counteranion were
refined anisotropically, whereas the positions of all hydrogen
atoms in the diamine ligands were generated geometrically, as-
signed isotropic thermal parameters, and allowed to ride on their
respective parent carbon atoms. A half molecule of dichlorome-
thane was found in the last Fourier map, which was refined aniso-
tropically. The carbon atom of this molecule lies on a special posi-
tion, and the chlorine atoms were disordered over two positions
with 60:40 occupancies. Their hydrogen atoms were included at
their idealized positions.
3
Elemental analyses were carried out on a EuroEA3000 Eurovector
Analyzer instrument. Electrospray-ionization mass spectra were re-
corded with a Quattro LC (quadrupole–hexapole–quadrupole)
mass spectrometer with an orthogonal Z-spray electrospray inter-
face (Micromass, Manchester, UK). The cone voltage was set at
À1
Ka
1
2
max./min.
residual
electron
density=1.497/
À3
2
0 V unless otherwise stated, with CH CN as the mobile-phase sol-
3
vent. Sample solutions were infused through a syringe pump di-
rectly connected to the ESI source at a flow rate of 10 mLmin ,
and a capillary voltage of 3.5 kV was used in the positive scan
mode. Nitrogen was employed as the drying and nebulizing gas.
Isotope experimental patterns were compared with theoretical pat-
À1
[20]
1
terns obtained by using the MassLynx 4.1 program.
H and
13
C NMR spectra were recorded on a Varian Innova 300 MHz spec-
1
13
trometer with CD Cl as the solvent. H– C gradient HSQC spectra
2
2
were recorded on a Varian Innova 500 MHz spectrometer with
CD Cl as the solvent. Gas chromatography analyses were per-
2
2
formed on an Agilent 7820 A GC system equipped with a flame
ionization detector and a capillary column (Agilent HP-5, 30 m
0
.32 mm0.25 mm). Mass determination was carried out on a GC-
CCDC 1054643 contains the supplementary crystallographic data
Mass Agilent 5973 network equipped with a mass-selective detec-
tor.
Catalyst preparation
Catalytic activity tests
Synthesis of [Mo S Cl (dmen) ]BF : A fivefold excess of PPh
3
General procedure for the reduction of nitroarenes: Under a nitro-
gen atmosphere, nitrobenzene (10 mL, 0.097 mmol), anisole (20 mL;
added as an internal standard), and Ph SiH (3.5 equiv.) were added
3
4
3
3
4
(
(
108 mg, 0.413 mmol) was added to an orange suspension of
nBu N) [Mo S Cl ] (100 mg, 0.083 mmol) in CH CN (12 mL) under
4
2
3
7
6
3
2
2
nitrogen. The color of the solution turned green immediately. After
to a green solution of [Mo S Cl (dmen) ]BF (4.4 mg, 0.0050 mmol)
3 4 3 3 4
ChemCatChem 2015, 7, 2675 – 2681
2679
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