title: Activation and deactivation of a robust immobilized Cp*Ir-transfer hydrogenation catalyst: a multielement in situ X-ray absorption spectroscopy study.
abstract: A highly robust immobilized [Cp*IrCl2]2 precatalyst on Wang resin for transfer hydrogenation, which can be recycled up to 30 times, was studied using a novel combination of X-ray absorption spectroscopy (XAS) at Ir L3-edge, Cl K-edge, and K K-edge. These culminate in in situ XAS experiments that link structural changes of the Ir complex with its catalytic activity and its deactivation. Mercury poisoning and "hot filtration" experiments ruled out leached Ir as the active catalyst. Spectroscopic evidence indicates the exchange of one chloride ligand with an alkoxide to generate the active precatalyst. The exchange of the second chloride ligand, however, leads to a potassium alkoxide-iridate species as the deactivated form of this immobilized catalyst. These findings could be widely applicable to the many homogeneous transfer hydrogenation catalysts with Cp*IrCl substructure.
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Sherborne
authors.forename: Michael R
authors.initials: MR
authors.lastname: Chapman
authors.forename: A John
authors.initials: AJ
authors.lastname: Blacker
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bourne
authors.affiliation: ‡School of Chemistry, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Chamberlain
authors.affiliation: §Yorkshire Process Technology Ltd., Leeds Innovation Centre, 103 Clarendon Road, Leeds, LS2 9DF, United Kingdom.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Crossley
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Lucas
authors.forename: Patrick C
authors.initials: PC
authors.lastname: McGowan
authors.affiliation: ⊥Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom.|#XMaS CRG, European Synchrotron Radiation Facility, 38043 Cedex, Grenoble, France.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Newton
authors.affiliation: §Yorkshire Process Technology Ltd., Leeds Innovation Centre, 103 Clarendon Road, Leeds, LS2 9DF, United Kingdom.
authors.forename: Thomas E O
authors.initials: TE
authors.lastname: Screen
authors.affiliation: ⊥Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom.|#XMaS CRG, European Synchrotron Radiation Facility, 38043 Cedex, Grenoble, France.
authors.forename: Paul
authors.initials: P
authors.lastname: Thompson
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Willans
authors.forename: Bao N
authors.initials: BN
authors.lastname: Nguyen
mesh_terms: D002384:Catalysis; D002712:Chlorides / Q000737:chemistry*; D006865:Hydrogenation; D007495:Iridium / Q000737:chemistry*; D008024:Ligands; D011188:Potassium / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D002712:Chlorides; D008024:Ligands; C538735:iridium chloride; D007495:Iridium; D011188:Potassium