Rhodium(I) carbonyl complexes of tetradentate chalcogen functionalized phosphines, [P(X)(CH2CH2P(X)Ph2)3] {X = O, S, Se}: Synthesis, reactivity and catalytic carbonylation reaction |
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Authors: | Biswajit Deb Kokil Saikia Rebecca AM Randall J Derek Woollins |
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Institution: | a Materials Science Division, Council of Scientific and Industrial Research, North East Institute of Science and Technology, Jorhat 785006, Assam, India b School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, UK |
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Abstract: | The reaction of Rh(CO)2Cl]2 with 0.5 mol equivalent of the ligands P′(X)(CH2-CH2P(X)Ph2)3](P′P3X4) {where X = O(a), S(b) and Se(c)} affords tetranuclear complexes of the type Rh4(CO)8Cl4(P′P3X4)] (1a-1c). The complexes 1a-1c have been characterized by elemental analyses, mass spectrometry, IR and multinuclear NMR spectroscopy, and the ligands b and c are structurally determined by single crystal X-ray diffraction. 1a-1c undergo oxidative addition (OA) reactions with CH3I to generate Rh(III) oxidised products. Kinetic data for the reaction of 1a and 1b with excess CH3I indicate a pseudo first order reaction. The catalytic activity of 1a-1c for the carbonylation of methanol to acetic acid and its ester show a higher Turn Over Frequency (TOF = 1349-1748 h−1) compared to the well-known species Rh(CO)2I2]− (TOF = 1000 h−1) under the similar experimental conditions. However, 1b and 1c exhibit lower TOF than 1a, which may be due to the desulfurization and deselinization of the ligands in the respective complexes under the reaction conditions. |
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Keywords: | Rhodium Carbonyl complex Chalcogen donor Functionalized phosphine Carbonylation |
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