Preparation
Synthesis of complex [Rh(COMe)ClI(2-Ph2PC6H4COOMe)-
(2-Ph2PC6H4COOMe)], 5
Ligands 2-Ph2PC6H4COOCH3 and 4-Ph2PC6H4COOCH3 were
prepared by a literature method.38 The starting complex
[Rh(CO)2Cl]2 was prepared by a known method.39
0.112 g (0.138 mmol) of complex 2 was dissolved in 10 cm3
CH2Cl2 and to this 6 cm3 CH3I was added. The reaction mixture
was then stirred at room temperature under nitrogen atmos-
phere for about 12 h and the solvent was evaporated under
vacuum. The yellow-reddish colored compound so obtained
was washed with diethyl ether and stored over silica gel in a
desiccator. Yield 0.106 g. [Found (calc. for C42H37ClIO5P2Rh):
C, 54.12 (53.17), H, 3.81 (3.90).] Selected IR data (KBr): 1672
[ν(COO)/cmϪ1]; 1717 [ν(CO)acyl/cmϪ1]; NMR data: 31P-{1H}
Synthesis of the complex [Rh(CO)Cl(2-Ph2PC6H4COOMe)], 1
[Rh(CO)2Cl]2 0.032 g (0.082 mmol) was dissolved in 10 cm3
CH2Cl2 and to this 0.053 g (0.164 mmol) of the ligand in 10 cm3
CH2Cl2 was added dropwise with constant stirring under
nitrogen atmosphere. The reaction mixture was stirred at room
temperature for about 1 h and the solvent was evaporated under
reduced pressure in a rotavapor to obtain a yellow solid. The
compound so obtained was washed with diethyl ether and
stored over silica gel in a desiccator. Yield 0.071 g, 83.5%.
[Found (calc. for C21H17ClO3PRh): C, 51.02 (51.84), H, 3.88
(3.49).] Selected IR data (KBr): 1979 [ν(CO)/cmϪ1], 1638
[ν(COO)/cmϪ1]. NMR: 31P-{1H) NMR δ 45.1 (d, 1JRh–P 162 Hz);
1H NMR δ 7.1–8.2 (m, 14 H, Ph), 4.1 (s, 3 H, –COOCH3).
1
1
1
δ 46.1 (d, JRh–P 162Hz); δ 39.5 (d, JRh–P 150 Hz); H NMR
δ 7.1–8.3 (m, 14H, Ph), 4.0 (s, 3H, COOCH3 chelated), 3.8
(s, 3H, COOCH3) and 2.3 (s, 3H, COCH3).
Reaction kinetics
The OA reactions of complexes 1 and 2 with CH3I were
monitored by using IR spectroscopy in a solution cell (1.0 mm
path length). 10 mg (mmol) of complexes 1 and 2 were added to
1 cm3 of neat CH3I at room temperature. An aliquot (0.5 ml) of
the reaction mixture was transferred by syringe into the IR cell.
Then the kinetic measurement were made by monitoring the
simultaneous decay of the terminal ν(CO) of the complexes in
the range 1925–2100 cmϪ1 and growth of the acyl ν(CO) of
the complex 4 and 5 in the range 1600–1750 cmϪ1. A series
of spectra were taken at regular intervals. The OA reactions of
CH3I with complexes 1 and 2 were found to be concentration
dependent on the complexes as well as on CH3I. Therefore, in
order to provide a pseudo-first order condition, the reaction
was carried out in a large excess of CH3I.
Synthesis of the complex trans-[Rh(CO)Cl(2-Ph2PC6H4-
COOMe)2], 2
[Rh(CO)2Cl]2 0.031 g (0.079 mmol) was dissolved in 10 cm3
CH2Cl2 and to this 0.102 g (0.318 mmol) of the ligand 2-Ph2-
PC6H4COOCH3 in 10 cm3 CH2Cl2 was added dropwise with
constant stirring under nitrogen atmosphere. The reaction
mixture was stirred at room temperature for about 1.5 h and the
solvent was evaporated under reduced pressure in a rotavapor
to obtain a light yellow solid. The compound so obtained
was purified by washing with diethyl ether. Suitable crystals
of the complex were developed by slow diffusion of (C2H5)2O
into a CH2Cl2 solution of the complex. Yield 0.108 g,
81.2%. [Found (calc. for C41H34ClO5P2Rh): C, 60.55 (61.02),
Carbonylation of methanol using complexes 1 and 2 as catalyst
precursors
H, 3.98 (4.22).] Selected IR data (KBr): 1949 [ν(CO)/cmϪ1];
1
1715 [ν(COO)/cmϪ1]; NMR data: 31P-{1H} δ 35.9 (d, JRh–P
=
0.099 mol of CH3OH, 0.016 mol of CH3I, 0.055 mol of H2O,
0.054 mmol of the complexes 1 or 2 were taken in the reactor
and then pressurized with CO gas (20 bar at room temperature,
0.080 mol). The reaction vessel was then placed into the heated
jacket of the autoclave and the reactions were carried out at
130 5 ЊC (corresponding pressure 35 2 bar) with variation
of reaction time. The products were collected and analyzed
by GC. The recycle experiments were done by maintaining
the same experimental conditions as described above with the
dark brown solid mass as catalyst obtained by evaporating the
carbonylation reaction mixture under reduced pressure.
136 Hz); 1H NMR δ 7.1–8.3 (m, 14 H, Ph), 3.7 (s, 3H,
COOCH3).
Synthesis of the complex trans-[Rh(CO)Cl(4-Ph2PC6H4-
COOCH3)2], 3
[Rh(CO)2Cl]2 0.026 g (0.066 mmol) was dissolved in 10 cm3
CH2Cl2 and to this 0.085 g (0.264 mmol) of the ligand 4-Ph2-
PC6H4COOCH3 in 10 cm3 CH2Cl2 was added dropwise with
constant stirring under nitrogen atmosphere. The reaction
mixture was stirred at room temperature for about 90 min and
the solvent was evaporated under reduced pressure in a
rotavapor to obtain a light yellow solid. The compound so
obtained was purified by washing with diethyl ether. Yield 0.091
g, 81.98%. [Found (calc. for C41H34ClO5P2Rh): C, 60.41 (61.02),
H, 3.96 (4.22).] Selected IR data (KBr): 1977 [ν(CO)/cmϪ1];
Acknowledgements
We are grateful for the financial support by the UK-India
Science & Technology Research Fund. Thanks are also due
to DST, New Delhi, OST, UK, RRL Jorhat (CSIR) and the
University of St. Andrews, UK.
1
1723 [ν(COO)/cmϪ1]; NMR data: 31P-{1H} δ 30.72 (d, JRh–P
127 Hz); 1H NMR δ 7.2–7.9 (m, 14 H, Ph), 3.7 (s, 3H,
COOCH3).
References
Synthesis of the complex
1 P. M. Maitlis, A. Haynes, G. J. Sunley and M. J. Howard, J. Chem.
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2 M. J. Howard, M. D. Jones, M. S. Roberts and S. A. Taylor, Catal.
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J. G. Sunley, J. Chem. Soc., Chem. Commun., 1995, 1579.
[Rh(COCH3)ClI(2-Ph2PC6H4COOCH3)], 4
The complex 1 0.105 g (0.216 mmol) was dissolved in 10 cm3
CH2Cl2 and to this 6 cm3 CH3I was added. The reaction mixture
was then stirred at room temperature under nitrogen atmos-
phere for about 6 h and the solvent was evaporated under
vacuum. The yellow-reddish colored compound so obtained
was washed with diethyl ether and stored over silica gel in a
desiccator. Yield 0.12 g. [Found (calc. for C22H20ClIO3PRh): C,
41.91 (42.04), H, 3.12 (3.18).] Selected IR data (KBr): 1641
[ν(COO)/cmϪ1]; 1677 [ν(CO)acyl/cmϪ1]; NMR data: 31P-{1H}
δ 47.9 (d, 1JRh–P 172 Hz); 1H NMR δ 7.02–8.1 (m, 14H, Ph), 4.2
(s, 3H, COOCH3), 2.3 (s, 3H, COCH3).
D a l t o n T r a n s . , 2 0 0 3 , 2 6 7 4 – 2 6 7 9
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Dutta, Dipak K.
