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P.J. Baricelli et al. / Journal of Organometallic Chemistry 694 (2009) 3381–3385
purchased from AGA-Gases, Venezuela. The FTIR spectra were re-
corded in a Perkin Elmer Spectrophotometer 1000 FTIR, using sam-
ples as KBr disks. NMR analyses were performed in a Bruker AM
300 spectrometer. GC analyses were carried out on a Hewlett Pack-
ard 5890 Series II chromatograph with a flame ionization detector
acetonitrile at 60 °C. The UV–Vis spectrum showed one adsorption
band at 332 nm assigned to LMCT characteristics of a Mo(0) center
coordinated with phosphorus ligand [10]. This band remains after
72 h at room temperature even at different dilutions of the com-
plex in acetone, which is indicative of the good stability of the
complex, demonstrating that it can be used as catalytic precursor
for reactions in homogeneous phase.
and an ultra 2.5% phenyl methyl silicone, 25 m, 320 lm column.
Quantification was achieved using the internal standard method
(naphthalene) and the peaks were identified by comparison with
pure samples analyzed by GC/MS HP 5890/5971 coupled system
The FTIR (Table 1) showed the characteristic bands of the PPh3
ligand at 1600–1700, 730 and 670 cmÀ1 assigned to the aromatic
ring symmetric stretching and symmetric and asymmetric hydro-
gen overtones. Also, there were three prominent bands observed
using a Quadex PONA 5% phenyl methyl silicone, 25 m, 320 lm
column. Atomic absorption analyses were performed with induc-
tive coupled plasma–optical emission spectrometry (ICP-OES), Per-
kin Elmer-Optima 3100 XL.
at 1897, 1840 and 1820 cmÀ1 corresponding to the
m
CO vibrations,
and a medium sharp band at 2020 cmÀ1 assigned to
nitrile coordinated to a metal center.
m
CN of aceto-
2.2. Synthesis of the complex Mo(CO)3(NCMe)(PPh3)2
The 1H NMR spectrum in deuterated chloroform showed a sin-
glet at 1.96 ppm which is assigned to the acetonitrile protons and a
multiplet centered at 7.30 ppm corresponding to the aromatic pro-
tons of the PPh3 ligand in the corresponding 1:10 ratio. The 31P
NMR (CDCl3) spectrum showed a singlet at 39.30 ppm assigned
to two equivalent P atoms coordinated to the Mo center. With all
the information obtained from the elemental analysis, UV–Vis,
FT-IR, 1H NMR, and 31P NMR, we propose the formulation Mo-
(CO)3(NCMe)(PPh3)2, which may present two possible structures:
one in which the two phosphine are in trans position and other
in which the two PPh3 ligands are in a mutually cis position and
each in trans position to a carbonyl ligand.
The Mo(CO)3(NCMe)3 complex was prepared and characterized
according the method reported by Tate et al. [9]. To a sample of
Mo(NCMe)3(CO)3 (0.24 g, 0.80 mmol) dissolved in acetonitrile
(10 mL) previously heated at 80 °C was added triphenylphosphine
(0.48 g, 1.83 mmol). The resulting solution was refluxed at 60 °C
with continuing stirring. After 12 h, a yellow-cream solid was fil-
tered off and washed with acetonitrile and dried under vacuum.
Yield 92%. Elemental Anal. Calc. for Mo(CO)3(NCMe)(PPh3)2: C,
66.05; H, 4.46; N, 1.88; Mo, 12.87. Found: C, 65.66; H, 4.46; N,
1.62; Mo, 12.86%.
2.3. X-ray crystallography
3.2. X ray structure
A
single crystal of Mo(CO)3(NCMe)(PPh3)2 (0.35 mm Â
The structure of complex Mo(CO)3(NCMe)(PPh3)2 was con-
firmed by single X-ray analysis. The ORTEP drawing is depicted
in Fig. 1 and the crystal data are summarized in Table 2. Crystals
of this complex were monoclinic and the structure was refined in
the space group P2(1)/c with four formula units per unit cell. The
crystal structure is constituted by isolated molecules with no unu-
sual intermolecular contacts; the coordination geometry around
the metal atom consists of a distorted octahedron with two tri-
phenylphosphine, three carbonyl and one acetonitrile ligand.
The two triphenylphosphine ligands are situated in the octahe-
dral structure in a cis arrangement and each phosphorus atom, P(1)
and P(2), in trans positions with respect to two carbonyl ligands,
C(1)O and C(3)O, respectively; the bond distances of Mo–P(1)
2.6273 Å and Mo–P(2) 2.7295 Å are longer than the distances of
the Mo–P bond trans to a carbonyl ligand reported for other similar
molybdenum complexes, such as cis-Mo(CO)4(PR3)2, PR3 = PMe2Ph
(2.525 and 2.533 Å), PMePh2 (2.545 and 2.565 Å) and PPh3 (2.576
0.38 mm  0.40 mm), obtained through crystallization from cold
acetonitrile, was selected under polarizing optical microscope and
glued on a glass fiber. The X-ray data was collected at room temper-
ature on a Rigaku AFC7S diffractometer with a Mercury CCD area
detector, using Mo K
a monochromated radiation (k = 0.71073 Å);
empirical absorption correction was applied. The structure was
solved by the direct method and refined by the full-matrix least-
squares method on F2, with anisotropic displacement parameters
for non-hydrogen atoms, using the SHELXTL crystallographic software
package. All hydrogen atoms on carbons were placed in their ideal
positions and refined as riding atoms with a uniform value of Uiso
The final refinement was converged to give R1 = 0.0915 and
wR2 = 0.1974 for all 7654 unique reflections.
.
2.4. Catalytic homogeneous hydrogenation
In a typical experiments, the catalyst precursor Mo(CO)3(NC-
Me)(PPh3)2 (0.015 g, 0.019 mmol), 1-hexene (1.3 mL, 10.5 mmol),
heptane (20 mL) and naphthalene (0.10 g) as internal standard
were introduced into a glass lined stainless steel autoclave (Parr,
50 mL) fitted with internal mechanical stirring, a temperature con-
trol unit and a sample valve. The solution was purged three times
with H2, then charged with the required pressure and heated to the
desired temperature. Samples of the reaction mixture were period-
ically extracted and the total pressure was adjusted via a high pres-
sure reservoir; once the samples were withdrawn from the
autoclave, they were cooled and analyzed by GC and GC–MS
techniques.
and
2.577 Å)
[11]
Mo(CO)5(5-methyldibenzophosphole)
(2.4899 Å) [12], Mo(CO)5[PPh2(o-C6H4OCH2OCH3)] (2.570 Å) [13]
and mer-Mo(CO)3[P(OPh)3]3 (2.3796, 2.4319 and 2.4390 Å) [14].
The main distortion from the ideal octahedral geometry is the
bending of the bulky phosphine ligands towards the C(1)–O and
C(3)–O ligands, in order to minimized steric repulsion [P(1)–Mo–
Table 1
Characterization of complex Mo(CO)3(NCMe)(PPh)2.
Spectroscopy analysis
FT-IR (cmÀ1
Assignment
)
1600–1700, 730, 670 m(aromatic)
1897, 1840, 1820
2020 (CN)
332 (LMCT)
m(CO)
m
3. Results and discussion
UV–Vis (nm)
1H NMR (ppm)
7.35 (m) (aromatic)
2.04 (s) (CH3)
37.73 (s) (coordinated phosphine)
38.51 (s) (coordinated phosphine)
3.1. Synthesis of the complex Mo(CO)3(NCMe)(PPh3)2
31P NMR (ppm)
The complex was obtained as yellow microcrystals by reacting
Mo(CO)3(NCMe)3 with two equivalents of triphenylphosphine in
(s) = singlet (m) = multiplet.