Dutta, D K and Chutia, P and Sharma, B J and Borah, B J and Woollins, J D
(2009)
Rohidium carbonyl complexes containing pyridine carboxylic acid ligands : reactivity towards various electrophiles and catalytic activity.
J Molecular Catalysis.A, 300.
pp. 29-35.
Abstract
The complex [Rh(CO)2Cl]2 reacts with two molar equivalent of pyridine carboxylic acids ligands
Py-2-COOH(a), Py-3-COOH(b) and Py-4-COOH(c) to yield rhodium(I) dicarbonyl chelate
complex [Rh(CO)2(L/)](1a) {L/ = �2-(N,O) coordinated Py-2-COO−(a/)} and non-chelate complexes
[Rh(CO)2ClL//](1b,c) {L// = �1-(N) coordinated Py-3-COOH(b), Py-4-COOH(c)}. The complexes 1 undergo
oxidative addition (OA) reactions with different electrophiles such as CH3I, C2H5I, C6H5CH2Cl and I2 to
give penta coordinated Rh(III) complexes of the types [Rh(CO)(CORn)XL/], {n = 1,2,3; R1 = CH3(2a);
R2 = C2H5(3a); X= I and R3 = CH2C6H5 (4a); X=Cl}, [Rh(CO)I2L/](5a), [Rh(CO)(CORn)ClXL//]
{R1 = CH3(6b,c); R2 = C2H5(7b,c); X= I and R3 = CH2C6H5 (8b,c); X=Cl} and [Rh(CO)ClI2L//](9b,c).
The complexes have been characterized by elemental analysis, IR and 1H NMR spectroscopy. Kinetic
data for the reaction of 1a–b with CH3I indicate a first order reaction. The catalytic activity of 1a–c for
the carbonylation of methanol to acetic acid and its ester is evaluated and a higher turn over number
(TON = 810–1094) is obtained compared with that of the well-known commercial species [Rh(CO)2I2]−
(TON = 653) at mild reaction conditions (temperature 130±5 ◦C, pressure 35±5 bar).
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