Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Physical Measurements
Procedure for catalytic transfer hydrogenation reaction
ESI-Mass spectra were recorded on a micromass Q-TOF mass
spectrometer with serial no. YA 263. Room temperature magnetic
moment measurement was carried out with a Gouy balance
The transfer hydrogenation of aldehydes and ketones were carried
out in isopropanol by using complex [1](ClO ) as catalyst assisted
4
2
by catalytic amount of a base following a general procedure. In a
schlenk tube, 1 mmol of the substrate (aldehyde/ketone),
(
Sherwood Scientific, Cambridge, U.K). NMR spectra were recorded
t
using either a Bruker Avance 400 MHz or 500 MHz spectrometers
0.005 mmol of the catalyst (4.5 mg) and 0.01 mmol of BuOK
using SiMe as the internal standard. Infrared spectra were obtained
(1.1 mg) were mixed in 10 mL of deaerated isopropanol. The
4
from
a
Perkin-Elmer 783 spectrophotometer.
A
Perkin-Elmer
reaction mixture was stirred at 82°C for 6 h under N pressure
2
Lambda 950 spectrophotometer was used to record UV-Vis spectra.
A Perkin-Elmer 240 C elemental analyzer was used to collect micro
analytical data (C, H, N). The electrochemical measurements were
performed using a PC-controlled PAR model 273 A electrochemistry
system. Cyclic voltammetric experiments were performed in
(unless stated otherwise). After the reaction was complete, the
evaporation of the solvent was done under reduced pressure
followed by purification of the resultant crude product on
preparative silica gel GF-254 TLC plate using 1:5 ethyl acetate:
hexane solvent mixture as eluent. The reduced products were
characterized by NMR spectroscopy (See Figures S7–S41).
acetonitrile solvent containing supporting electrolyte, 0.1 M [Bu N]
4
PF under nitrogen atmosphere and the three electrodes config-
6
uration includes Ag/AgCl as the reference electrode,Pt disk as the
working electrode and Pt wire as the auxiliary electrode. E1/2 for the
ferrocenium-ferrocene couple was 0.40 V under the experimental
condition.
Mechanistic analysis
In a sealed NMR tube 0.05 mmol isopropanol (3.0 mg) was mixed
with 0.05 mmol of catalyst [1] (45.0 mg) and 0.01 mmol of BuOK
2
+
t
(
1.2 mg) in 0.7 ml THF-d . A distinct resonance of RuÀ H was
8
1
observed at δ=À 4.03 ppm (Figure S30a) in the H-NMR spectrum
Synthesis and Characterization Data of Complex [1](ClO4)2
recorded instantaneously. After 30 min, the solution was subjected
The ligand, 2,6-bis(phenylazo)pyridine (L) was prepared following
the method available in the literature where the synthetic route
involves the condensation of nitrosobenzene with 2,6-diaminopyr-
to IR spectral analysis which showed two distinct peaks at 2844 and
À 1
2902 cm
characteristic to NÀ H stretching for the hydrazo
intermediate (Figure S31a). A similar experiment was carried out
with appropriate quantity of catalyst [1] (45.0 mg) and isopropa-
[4]
2+
idine in 2:1 molar ratio in highly alkaline condition. 75 mg
0.26 mmol) of the ligand, L and 65 mg (0.25 mmol) of RuCl .xH O
2
(
nol-d in THF. A broad signal at δ=À 1.50 ppm, appeared in the H-
3
2
8
was mixed in 10 mL of ethanol and PMe Ph (138 mg, 1.0 mmol) was
NMR of the reaction mixture, is characteristic to RuÀ D resonance
(Figure S30b) and two distinct IR bands appeared due to NÀ D
2
added to the solution in excess. The solution was refluxed for 2 h.
The resulting reddish brown solution was then concentrated using
a rotary evaporator and was added into a saturated aqueous
À 1
stretching at 2148 and 2246 cm in its IR spectrum after stirring
the reaction mixture for 30 min (Figure S31b).
solution (cold) of NaClO . The brown precipitate, thus deposited,
4
was washed thoroughly with cold water, hexane to remove any
impurity present and then dried under vacuum. The crude mass
was recrystallized from slow evaporation of its acetonitrile solution
at room temperature (300 K). Yield: 131 mg (58%, based on Ru).
Computational details
All the calculations were performed using Gaussian 09 program
[22]
2
+
À 1
package. The 6-31G* (C, H, N), 6-311G* (P, Cl) and SDD (Ru) level
[23]
ESI-MS: m/z 332 amu for [1-CH CN] . IR (KBr, cm ): 1428 (νN=N).
3
of theory
were employed for the structural optimization and
Anal. Calc. for C H Cl N O P Ru: C, 46.47; H, 4.23; N, 9.29. Found: C,
3
5
38
2
6
8 2
1
vibrational analysis. Spin restricted approaches were employed for
ground state singlet state. Singlet excitation energies based on the
solvent-phase (acetonitrile) optimized geometry of the complexes
were computed using the Time Dependent Density Functional
4
6.71; H, 4.42; N, 9.11. H-NMR (500 MHz, CDCl ): δ (ppm) 8.80 (d,
3
J=7.5 Hz, 4H), 8.24 (d, J=8.0 Hz, 2H), 8.02 (t, J=8.0 Hz, 1H), 7.68 (t,
J=8.0 Hz, 2H), 7.59 (t, J=8.0 Hz, 4H), 7.15 (t, J=7.5 Hz, 2H), 6.98 (t,
3
1
J=8.0 Hz, 4H), 6.23-6.19 (m, 4H), 2.65 (s, 3H), 1.66 (s, 12H). P-NMR
162 MHz, CDCl ): δ 37.91 ppm.
[22,24]
Theory (TD-DFT) formalism
in dichloromethane/acetonitrile
(
3
solvent using Conductor-like Polarisable Continuum Model
[24a,25]
[26]
(CPCM).
GaussSum was used to calculate the percentage
contribution of metal and ligand to the frontier orbital and the
fractional contributions of various molecular orbital in the optical
spectral transition.
X-Ray Crystallography
Crystallographic data table for complex [1](ClO4)2 and selected
bond parameters are provided in the Supporting Information
(
Tables S1–S2). Suitable crystals for X-ray diffraction analysis were
developed by slow evaporation of the acetonitrile solution of the
complex. Crystallographic data were collected on a Bruker SMART
APEX-II diffractometer, equipped with graphite-monochromatic Mo
Kα radiation (λ=0.71073 Å), and was corrected for Lorentz polar-
ization effects. Data for [1](ClO ) : a total of 27504 reflections were
collected, of which 6822 were unique (Rint =0.172). These satisfy the
I >2σ(I) criterion and was used in subsequent analysis. The
structure was solved by employing the SHELXS-2014 program
Supporting Information
The supporting information contains spectroscopic characteriza-
tions of the Ru-complex and intermediates, voltammetric and
crystallographic details of the Ru-complex, and NMR spectra of the
products. Crystallographic data for complex [1](ClO4)2 has been
deposited with Cambridge Crystallographic Data Centre as supple-
mentary publication no. CCDC 2065125. Copies of the data can be
obtained free of charge on application to CCDC.
4
2
2
package and was refined by full-matrix least squares based on F
[21]
(SHELXL-2014).
All hydrogen atoms were added at calculated
positions. Crystal twining has been observed for the counter anions
and phenyl ring of one of the PMe Ph ligand. However, we use this
data as we have failed to produce better quality crystals for
diffraction after repetitive attempts.
2
Acknowledgements
The research was supported by the department of science and
technology (DST), India, SR/S2/JCB-09/2011, EMR/2014/000502.
Z. Anorg. Allg. Chem. 2021, 1–8
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