title: Iridium Cyclooctene Complex That Forms a Hyperpolarization Transfer Catalyst before Converting to a Binuclear C-H Bond Activation Product Responsible for Hydrogen Isotope Exchange.
abstract: [IrCl(COE)2]2(1) reacts with pyridine (py) and H2to form crystallographically characterized IrCl(H)2(COE)(py)2(2). 2 undergoes py loss to form 16-electron IrCl(H)2(COE)(py) (3), with equivalent hydride ligands. When this reaction is studied with parahydrogen, 1 efficiently achieves hyperpolarization of free py (and nicotinamide, nicotine, 5-aminopyrimidine, and 3,5-lutudine) via signal amplification by reversible exchange (SABRE) and hence reflects a simple and readily available precatayst for this process. 2 reacts further over 48 h at 298 K to form crystallographically characterized (Cl)(H)(py)(μ-Cl)(μ-H)(κ-μ-NC5H4)Ir(H)(py)2(4). This dimer is active in the hydrogen isotope exchange process that is used in radiopharmaceutical preparations. Furthermore, while [Ir(H)2(COE)(py)3]PF6(6) forms upon the addition of AgPF6to 2, its stability precludes its efficient involvement in SABRE.
authors.affiliation: Centre for Hyperpolarization in Magnetic Resonance, University of York , York YO10 3NR, U.K.
authors.forename: Wissam
authors.initials: W
authors.lastname: Iali
authors.affiliation: Centre for Hyperpolarization in Magnetic Resonance, University of York , York YO10 3NR, U.K.
authors.forename: Gary G R
authors.initials: GG
authors.lastname: Green
authors.affiliation: Centre for Hyperpolarization in Magnetic Resonance, University of York , York YO10 3NR, U.K.
authors.forename: Sam J
authors.initials: SJ
authors.lastname: Hart
authors.affiliation: Centre for Hyperpolarization in Magnetic Resonance, University of York , York YO10 3NR, U.K.
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Whitwood
authors.affiliation: Centre for Hyperpolarization in Magnetic Resonance, University of York , York YO10 3NR, U.K.
authors.forename: Simon B
authors.initials: SB
authors.lastname: Duckett