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RESEARCH PRODUCT

Synthesis, characterization and kinetics of the metallation of the intermediate compound to produce compound · (H2O) from Rh(II) tetraacetate

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Abstract Photochemical irradiation of mixtures of [Rh2(μ-O2CCH3)4]·(HOCH3)2 and P(2-(CH3O)C6H4)Ph2 (POMe) in CH2Cl2 solution (1:1 molar ratio) yields quantitatively compound [ Rh 2 (μ- O 2 CCH 3 ) 3 ( O 2 CCH 3 )(η 2 - P (2-( CH 3 O ) C 6 H 4 ) Ph 2 ]·( H 2 O ) (1) containing a POMe acting as a chelating equatorial ( P ) axial ( O ) donor ligand. This compound undergoes intramolecular CH activation reaction at one of the phenyl rings in CHCl3 or CH3COOH/toluene solution at room temperature to form the monometallated compound [ Rh 2 (μ- O 2 CCH 3 ) 3 (μ-( C C 3 H 4 ) P (2-( CH 3 O C 6 H 4 ) Ph )]· ( H 2 O ) ( 2 ). The kinetics of the 1 → bd2 reaction have been studied in acid media (CH3COOH, CH3COOD, CH3COOH/CF3SO3H, CH3COOH/toluene) and aprotic solvents (chloroform, toluene) at variable temperatures and pressures: the results are interpreted in view of those published for similar dinuclear Rh(II) compounds. The values found for δH*, ΔS* and ΔV* (84 kJmol1 −51 J K−1 mol−1, 1.3 cm3 mol−1 in CH3COOH; and 68 kJ mol−1, −121 J K−1 mol−1, −15 cm3 mol−1 in aprotic solvents) agree with those found for similar monometallation reactions studied on Rh(II)2 core compounds. The more positive values found in this study for ΔS* and ΔV* could be attributed both to a bond-breaking expansion of the axial RhO(phosphine) bond and to the transfer of the monodentated acetato ligand from a tight inert equatorial coordination position to a labile axial position. Compound 1 has to undergo these processes in order to reach the highly ordered transition state needed for the CH bond activation to take place if the steric demands of the phosphine ligand are taken into account.