@article {1481, title = {Catalyst poisoning in catalyzed imine hydrogenation: A novel zwitterionic Rh(I)/o-hydroxy-substituted imine complex}, journal = {Journal of Molecular Catalysis a-Chemical}, volume = {257}, number = {1-2}, year = {2006}, note = {ISI Document Delivery No.: 089DITimes Cited: 3Cited Reference Count: 38Marcazzan, Paolo Patrick, Brian O. James, Brian R.}, month = {Sep}, pages = {26-30}, type = {Article}, abstract = {During investigation of the homogeneous H-2-hydrogenation of the ketimine (o-HOC6H4)C(Me)=NCH2Ph catalyzed by the [Rh(COD)(PPh3)(2)]PF6 precursor in MeOH at ambient conditions, we have isolated [Rh{eta(4)-(C6H4O)C(-)(Me)=N(+)(H)CHPh}(PPh3)(2)]PF6 (3), an unusual zwitterionic Rh complex in which the imine is coordinated via the C-4 part of the o-hydroxy-arene moiety in a quinoid form; this tautomer is generated via proton transfer from the O-atom to the N-atom within the molecular, benzenoid form. Precipitation of 3 from the MeOH solution, even under H-2, causes sequestration of the Rh and complete suppression of the catalytic activity. (In a previously studied system with the corresponding, non-hydroxy-substituted ketimine, PhC(Me) = NCH2Ph, the Rh was sequestered as an inactive o-metalated species). The solid state structure of 3 is retained in CH2Cl2 solution, but in MeOH and Me2CO reversible loss of the ketimine generates the cis-[Rh(PPh3)(2)(solvent)(2)]PF6 species. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {amine, BEHAVIOR, CATALYSIS, CATIONIC RHODIUM COMPLEXES, CHEMICALS, FINE, HYDROGENATION, HYDROLYSIS, imine complex, LIGAND, LIGANDS, OLEFINS, phosphine, RHODIUM COMPLEX, SCHIFF-BASES, SELECTIVE HYDROGENATION, zwitterion}, isbn = {1381-1169}, url = {://000240860100005}, author = {Marcazzan, P. and Patrick, B. O. and James, Brian R.} }