S.O. Akiri and S.O. Ojwach
Journal of Organometallic Chemistry 942 (2021) 121812
used homogeneous [32-37] and supported [38] catalyst systems
in the methoxycarbonylation of olefins with varied catalytic activi-
ties and region-selectivities. In this current contribution, we report
the design of water soluble palladium(II) complexes and their ap-
plications as biphasic catalysts in the methoxycarbonylation of 1-
hexene. The non-water soluble palladium(II) analogues have also
been studied for comparison purposes. Detailed structural studies
of the palladium(II) complexes, influence of catalyst structure on
catalytic behaviour and catalyst recycling have been investigated
and are herein discussed.
2.3. Synthesis of water-soluble (phenoxy)imine palladium(II)
complexes
2.3.1. Sodium
(E)−4–hydroxy-3-((phenylimino)methyl)benzenesulfonate
palladium(II) (PdL1)
To a solution of Pd(OAc)2 (0.07 g, 0.31 mmol) in methanol
(10 ml), was added
a solution of L1 (0.19 g, 0.62 mmol) in
methanol (5 ml). The mixture was then stirred under nitrogen
atmosphere for 24 h to give a yellow mixture, which was fil-
tered and recrystallized using small portions of hexane to afford
a bright yellow solid. Yield = 0.17 g (78%). 1H NMR (400 MHz,
2. Experimental section
3
DMSO): δH (ppm); 5.85 (d, 2H, JHH = 8.80 Hz, 6PhO), 7.34–7.47
4
2.1. Instrumentation and general materials
(m, 12H, Ar) 7.71 (d, 2H, JHH = 2.28 Hz, 3-PhO), 8.07 (s, 2H,
13
–
Himine). C NMR (100 MHz, DMSO, δ ppm): 164.6 (CH N), 164.2
The reagents aniline (>99.5%), 2,6- dimethyl aniline (99%), 2, 6-
diisopropylaniline (90%), salicylaldehyde (98%), sodium carbonate,
glacial acetic acid (>98%), palladium acetate (98%), sulphuric acid,
2-methoxyethylamine (98%) were purchased from Sigma-Aldrich
and were used as received without further purification. Sodium
3-formyl-4-hydroxybenzenesulfonate was synthesised following a
modified route of a previously reported procedure. All solvents
purchased from Merck were of analytical grade and were dried
before use. Toluene solvent was dried over sodium wire and ben-
zophenone while methanol was dried and distilled by heating over
magnesium metal activated with iodine. Dichloromethane was dis-
tilled using phosphorus pentoxide and stored in molecular sieves.
Ligands L4 and L5 and their respective complexes PdL4 and PdL5,
having been reported before [39] were synthesised and used for
comparison purposes with their water soluble analogues. 1H NMR
and 13C NMR spectra were recorded on a Bruker Ultrashield 400
(1H NMR 400 MHz, 13C NMR 100 MHz) spectrometer in CDCl3
and DMSO solution at room temperature. The chemical shift val-
ues (δ) were referenced to the residual proton and carbon signals
at 7.24 and 77.0 ppm, respectively of the CDCl3 NMR solvent and
2.50 and 39.52 ppm for DMSO. The infrared spectra were recorded
on a Perkin-Elmer Spectrum 100 in the 4000–400 cm−1 range.
Mass spectral analyses were carried out using LC premier Micro-
mass, Elemental analyses were performed on a Thermal Scientific
Flash 2000 whereas GC and GC–MS analyses was performed on a
Varian CP-3800 and QP2010 respectively. X-ray data were recorded
on a Bruker Apex Duo diffractometer equipped with an Oxford In-
strument.
–
(C O), 149.2 (Ar-C), 136.2 (C-SO3),133.4 (Ar-C), 132.7 (Ar-C), 128.4
(Ar-C), 126.8 (Ar-C), 125.1 (Ar-C), 119.2 (Ar-C), 119.1 (Ar-C).IR νmax
cm−1: ν(C
Calc. for C26H18 N2Na2O8PdS2. 10H2O: C, 35.36; H, 4.34; N, 3.17.
Found: C, 35.53; H, 4.08; N, 3.11.
/
= 1605, ESI-MS (m/z) = 678([M-Na]+, 95%). Anal.
=
N
)
2.3.2. Sodium (E)−3-(((2,6-dimethylphenyl)imino)methyl)
benzenesulfonate palladium(II) (PdL2)
Complex PdL2 was synthesized following the method outlined
for PdL1 using Pd(OAc)2 (0.05 g, 0.22 mmol) and L2 (0.14 g,
0.44 mmol). Yield = 0.13 g (81%). 1H NMR (400 MHz, DMSO):
3
δH (ppm); 2.14 (s, 12H, Ar-CH3), δH 5.78 (d, 2H, JHH = 8.8 Hz,
3
Ar), 6.80 (d, 2H, JHH = 7.2 Hz, Ar), 7.34–7.47 (m, 6H, Ar) 7.65 (d,
2H, JHH = 2.0 Hz, Ar), 7.89 (s, 2H, Himine). 13C NMR (100 MHz,
3
–
–
DMSO, δ ppm): 166.1 (CH N), 162.9 (C O), 149.1 (Ar-C), 146.1 (C-
SO3), 136.2 (Ar-C), 133.7(Ar-C), 128.1 (Ar-C), 124.6 (Ar-C), 121.1
cm−1
–
/ :
(Ar-C), 119.1 (Ar-C), 115.1 (Ar-C), 23.5 (C H3) IR νmax
ν(C N) = 1607, ESI-MS (m/z) = 780.99 ([M+Na]+, 25%). Anal. Calc.
=
for C30H26N2Na2O8PdS2. 2H2O: C, 45.32; H, 3.80; N, 3.52. Found: C,
45.47; H, 3.70; N, 3.67.
2.3.3. Sodium
(E)−3-(((2,6-diisopropylphenyl)imino)methyl)benzenesulfonate (PdL3)
Compound PdL3 was synthesized using the method described
for PdL1 using Pd(OAc)2 (0.05 g, 0.22 mmol) and L3 (0.17 g,
0.44 mmol). Yield = 0.16 g (84%). 1H NMR (400 MHz, DMSO):
3
δH (ppm); 1.16 (d, 24H, JHH
=
6.8 Hz ipr), 3.05 (m, 4H,
3
CH3CH3CH), δH 5.73 (d, 2H, JHH = 8.8 Hz, Ar), 6.80 (d, 2H,
3JHH = 7.2 Hz, Ar), 7.34–7.47 (m, 6H, Ar) 7.65 (d, 2H, JHH = 2.0 Hz),
3
7.95 (s, 2H, Himine). 13C NMR (100 MHz, DMSO, δ ppm): 165.4
2.2. Single crystal X-ray crystallography
–
–
(CH N), 162.7(C O), 146.1 (Ar-C), 140.2 (C-SO3), 134.4 (Ar-C),
X-ray data for complexes were recorded on a Bruker Apex Duo
diffractometer equipped with an Oxford Instruments Cryojet oper-
ating at 100(2) K and an Incoatec microsource operating at 30 W
133.7 (Ar-C), 128.1 (Ar-C), 124.6 (Ar-C), 123.5 (Ar-C), 120.7(Ar-
–
–
C), 119.2 (Ar-C), 31.2 (C CH3), 28.1 (C H3). IR νmax
/ :
cm−1
ν(C
N) = 1604. ESI-MS (m/z) = 893.20 ([M+Na]+, 100%). Anal.
=
˚
power. The data were collected with Mo Kα (λ = 0.71073 A) ra-
Calc. for C38H42N2Na2O8PdS2. 2H2O: C, 50.30; H, 5.11; N, 3.09.
Found: C, 50.21; H, 4.95; N, 3.33.
diation at a crystal-to-detector distance of 50 mm. The follow-
ing conditions were used for the data collection: omega and phi
scans with exposures taken at 30 W X-ray power and 0.50° frame
widths using APEX2[40]. The data were reduced with the pro-
gramme SAINT [41] using outlier rejection, scan speed scaling,
as well as standard Lorentz and polarisation correction factors. A
SADABS semi-empirical multi-scan absorption correction was ap-
plied to the data. Direct methods, SHELXS-2014 and WinGX were
used to solve all three structures. All non-hydrogen atoms were
located in the difference density map and refined anisotropically
with SHELXL-2014. All hydrogen atoms were included as idealised
contributors in the least squares process. Their positions were cal-
2.3.4. (E)−2-(((2,6-diisopropylphenyl)imino)methyl)phenol
palladium(II) (PdL6)
Complex PdL6 was synthesized following the procedure used
for PdL4 using Pd(OAc)2 (0.17 g, 0.44 mmol) and L6 (0.25 g,
0.88 mmol). Yield = 0.25 g (84%). 1H NMR (400 MHz, CDCl3): δH
3
(ppm); 1.20 (d, 24 H, JHH = 5.4 Hz, ipr), 3.54 (m, 4H, CH3CH3CH)
3
6.01 (d, 2H, JHH = 6.72 Hz, 4-PhO), 6.46 (m, 2H, 4-PhO),7.10
3
(m, 4H, 3,5-pH), 7.21 (d, 4H, JHH = 6.2 Hz, 5-PhO, 4Ph), 7.35 (t,
3
2H, JHH = 6.12 Hz 3-PhO), (s, 2H, Himine). 13C NMR (100 MHz,
–
–
CDCl3, δ ppm):165.5 (CH N), 162.7 (C O), 144.8 (Ar-C), 142.4 (Ar-
–
culated using a standard riding model with C Haromatic distances
C), 134.8 (Ar-C), 134.3 (Ar-C), 126.6(Ar-C), 122.8 (Ar-C)120.8 (Ar-
˚
˚
of 0.93 A and Uiso= 1.2 Ueq, C–Hmethylene distances of 0.99 A and
Uiso= 1.2 Ueq and C–Hmethyl distances of 0.98 A and Uiso= 1.5
C), 119.5 (Ar-C),114.2 (Ar-C), 28.8 (C(CH3)2) 24.3 (C-iPr): IR νmax
/
cm−1: ν(C N) = 1603. Anal. Calc. for C38H44N2O2Pd: C, 68.41; H,
˚
=
Ueq.
6.65; N, 4.20. Found: C, 68.36; H, 6.70; N, 4.26.
2