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Deb B.,North East Institute of Science and Technology Council of Scientific and Industrial Research | Dutta D.K.,North East Institute of Science and Technology Council of Scientific and Industrial Research
Journal of Molecular Catalysis A: Chemical | Year: 2010

The dimeric rhodium precursor [Rh(CO)2Cl]2 reacts with two molar equivalent of 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene [xantphos] (a), bis(2-diphenylphosphinophenyl)ether [DPEphos] (b) and their corresponding dioxide analogues xantphos dioxide (c), DPEphos dioxide (d) to afford the mono- and dicarbonyl complexes of the type [Rh(CO)Cl(L)] (1a,1b) and [Rh(CO)2Cl(L)] (1c,1d) respectively, where L = a-d. The complexes 1a-1d have been characterized by elemental analyses, IR and NMR (1H, 31P and 13C) spectroscopy, and the structure of the ligand d was determined by single crystal X-ray diffraction. 1a-1d undergo oxidative addition (OA) reactions with different electrophiles such as CH3I, C2H5I and I2 to give Rh(III) complexes of the types [Rh(CO)y(COR)ClXL] {R = -CH3 (2a-2d), -C2H5 (3a-3d); X = I and y = 0, L = a, b; y = 1, L = c, d} and [Rh(CO)ClI2L] (4a-4d) respectively. Kinetic data for the reactions of 1a-1d with CH3I indicate a pseudo-first-order reaction. The catalytic activity of 1a-1d for the carbonylation of methanol to acetic acid and its ester was evaluated at different CO pressure 15, 20 and 33 bar at 130 °C and a higher Turn Over Number (TON) (679-1768) were obtained compared to that of the well-known commercial species [Rh(CO)2I2]- (TON = 463-1000) in each case under the similar experimental conditions. © 2010 Elsevier B.V. All rights reserved. Source


Borah B.J.,North East Institute of Science and Technology Council of Scientific and Industrial Research | Deb B.,North East Institute of Science and Technology Council of Scientific and Industrial Research | Sarmah P.P.,North East Institute of Science and Technology Council of Scientific and Industrial Research | Dutta D.K.,North East Institute of Science and Technology Council of Scientific and Industrial Research
Journal of Molecular Catalysis A: Chemical | Year: 2010

The new complexes of the type [Rh(CO)2ClL] (1a-c), where L = 2-Benzoylpyridine (a), 3-Benzoylpyridine (b) and 4-Benzoylpyridine (c) have been synthesized and characterized. Oxidative addition (OA) of 1a-c with CH3I, C2H5I and C6H5CH2Cl afford penta coordinated Rh(III) complexes, [Rh(CO)(CORn)ClXL]{R1 = -CH3 (2a-c), R2 = -C2H5 (3a-c); X = I and R3 = -CH2C6H5 (4a-c); X = Cl}. Kinetic data for the reaction of 1a-c with CH3I indicate a pseudo-first order reaction. The 1a-c exhibit high catalytic activity in the carbonylation of methanol to acetic acid and its ester and show a higher turn over number (TON = 1529-1748) than the well known commercial species [Rh(CO)2I2]- (TON = 1000) under the reaction conditions: temperature 130 ± 2 °C, pressure 30 ± 2 bar and time 1 h. © 2009 Elsevier B.V. All rights reserved. Source


Sarmah P.P.,North East Institute of Science and Technology Council of Scientific and Industrial Research | Deb B.,North East Institute of Science and Technology Council of Scientific and Industrial Research | Borah B.J.,North East Institute of Science and Technology Council of Scientific and Industrial Research | Fuller A.L.,University of St. Andrews | And 3 more authors.
Journal of Organometallic Chemistry | Year: 2010

The dimeric rhodium precursor [Rh(CO)2Cl]2 reacts with quinoline (a) and its three isomeric carboxaldehyde ligands [quinoline-2-carboxaldehyde (b), quinoline-3-carboxaldehyde (c), and quinoline-4-carboxaldehyde (d)] in 1:2 mole ratio to afford complexes of the type cis-[Rh(CO)2Cl(L)] (1a-1d), where L = a-d. The complexes 1a-1d have been characterised by elemental analyses, mass spectrometry, IR and NMR (1H, 13C) spectroscopy together with a single crystal X-ray structure determination of 1c. The X-ray crystal structure of 1c reveals square planar geometry with a weak intermolecular pseudo dimeric structure (Rh⋯Rh = 3.573 ). 1a-1d undergo oxidative addition (OA) with different electrophiles such as CH3I, C2H5I and I 2 to give Rh(III) complexes of the type [Rh(CO)(COR)Cl(L)I] {R = -CH3 (2a-2d), R = -C2H5 (3a-3d)} and [Rh(CO)Cl(L)I2] (4a-4d) respectively. 1b exhibits facile reactivity with different electrophiles at room temperature (25 °C), while 1a, 1c and 1d show very slow reactivity under similar condition, however, significant reactivity was observed at a temperature ∼40 °C. The complexes 1a-1d show higher catalytic activity for carbonylation of methanol to acetic acid and methyl acetate [Turn Over Frequency (TOF) = 1551-1735 h-1] compared to that of the well known Monsanto's species [Rh(CO)2I 2]- (TOF = 1000 h-1) under the reaction conditions: temperature 130 ± 2 °C, pressure 33 ± 2 bar, 450 rpm and time 1 h. The organometallic residue of 1a-1d was also isolated after the catalytic reaction and found to be active for further run without significant loss of activity. © 2010 Elsevier B.V. All rights reserved. Source

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