32354-36-2Relevant academic research and scientific papers
Direct observation of aldehyde insertion into rhodium-aryl and -alkoxide complexes
Krug, Christopher,Hartwig, John F.
, p. 1674 - 1679 (2007/10/03)
Several organorhodium(I) complexes of the general formula (PPh3)2(CO)RhR (R = p-tolyl, o-tolyl, Me) were isolated and were shown to insert aryl aldehydes into the aryl-rhodium(I) bond. Under nonaqueous conditions, these reactions provided ketones in good yield. The stability of the arylrhodium(I) complexes allowed these reactions to be run also in mixtures of THF and water. In this solvent system, diarylmethanols were generated exclusively. Mechanistic studies support the formation of ketone and diarylmethanol by insertion of aldehyde into the rhodium-aryl bond and subsequent β-hydride elimination or hydrolysis to form diaryl ketone or diarylmethanol products. Kinetic isotope effects and the formation of diarylmethanols in THF/water mixtures are inconsistent with oxidative addition of the acyl carbon-hydrogen bond and reductive elimination to form ketone. Moreover, the intermediate rhodium diarylmethoxide formed from insertion of aldehyde was observed directly during the reaction. Its structure was confirmed by independent synthesis. This complex undergoes β-hydrogen elimination to form a ketone. This alkoxide also reacts with a second aldehyde to form esters by insertion and subsequent β-hydrogen elimination. Thus, reactions of arylrhodium complexes with an excess of aldehyde formed esters by a double insertion and β-hydrogen elimination sequence.
Relative affinities of carbonylbis(triphenylphosphine)rhodium(I) and related cations for anionic ligands in CH2Cl2
Araghizadeh, Farshid,Branan, Daniel M.,Hoffman, Norris W.,Jones, John H.,McElroy, E. Andrew,Miller, Nathan C.,Ramage, David L.,Salazar, Anna Battaglia,Young, Sidney H.
, p. 3752 - 3755 (2008/10/08)
Infrared spectroscopy has been used to determine the relative anion affinities in CH2Cl2 of Rh(PPh3)2(CO)+ and Rh(AsPh3)2(CO)+ via measurement of equilibrium constants for the metatheses RhL2(CO)Y + PPN+Z- = RhL2(CO)Z + PPN+Y-. Observed for L = PPh3 was the anion affinity trend NCO- ? O2CMe- ～ O2CPh- ? F- ～ NCS- > Cl- > Br- > I- ? ONO2- ～ O2CCF3- ? OTf- ～ OClO3-. A smaller series for L = AsPh3 displayed a similar trend, but with positions of NCS- and Cl- reversed. For most anion pairs studied, the equilibrium lies so far to the left or right that only limits could be calculated, given the inherent experimental limitations. For L = PPh3, the equilibrium constant for replacement of the least preferred anion by the most can be inferred as >1019. Rh(PCy3)2(CO)Cl and Rh(PCy3)2(CO)Z (Z = NCS, NCSe, O2CMe; but not F, O2CPh, and NCO) interact strongly in solution and thus limit study of that series.
