Metal-mediated catalytic polarisation transfer from parahydrogen to 3,5-dihalogenated pyridines

TY - JOUR

T1 - Metal-mediated catalytic polarisation transfer from parahydrogen to 3,5-dihalogenated pyridines

AU - Tickner, Ben J

AU - Dennington, Marcus

AU - Collins, Benjamin G

AU - Gater, Callum A

AU - Tanner, Theo F N

AU - Whitwood, Adrian C

AU - Rayner, Peter J

AU - Watts, Daniel P

AU - Duckett, Simon B

N1 - © 2024 The Authors. Published by American Chemical Society.

PY - 2024/1/19

Y1 - 2024/1/19

N2 - The neutral catalysts [IrCl(H) 2(NHC)(substrate) 2] or [IrCl(H) 2(NHC)(substrate)(sulfoxide)] are used to transfer polarization from para hydrogen ( pH 2) to 3,5-dichloropyridine and 3,5-dibromopyridine substrates. This is achieved in a rapid, reversible, and low-cost process that relies on ligand exchange within the active catalyst. Notably, the sulfoxide-containing catalyst systems produced NMR signal enhancements between 1 and 2 orders of magnitude larger than its unmodified counterpart. Consequently, this signal amplification by reversible exchange hyperpolarization method can boost the 1H, 13C, and 15N nuclear magnetic resonance (NMR) signal intensities by factors up to 4350, 1550, and 46,600, respectively (14.0, 1.3, and 15.4% polarization). In this paper, NMR and X-ray crystallography are used to map the evolution of catalytically important species and provide mechanistic rational for catalytic efficiency. Furthermore, applications in spontaneous radiofrequency amplification by stimulated emission and NMR reaction monitoring are also shown.

AB - The neutral catalysts [IrCl(H) 2(NHC)(substrate) 2] or [IrCl(H) 2(NHC)(substrate)(sulfoxide)] are used to transfer polarization from para hydrogen ( pH 2) to 3,5-dichloropyridine and 3,5-dibromopyridine substrates. This is achieved in a rapid, reversible, and low-cost process that relies on ligand exchange within the active catalyst. Notably, the sulfoxide-containing catalyst systems produced NMR signal enhancements between 1 and 2 orders of magnitude larger than its unmodified counterpart. Consequently, this signal amplification by reversible exchange hyperpolarization method can boost the 1H, 13C, and 15N nuclear magnetic resonance (NMR) signal intensities by factors up to 4350, 1550, and 46,600, respectively (14.0, 1.3, and 15.4% polarization). In this paper, NMR and X-ray crystallography are used to map the evolution of catalytically important species and provide mechanistic rational for catalytic efficiency. Furthermore, applications in spontaneous radiofrequency amplification by stimulated emission and NMR reaction monitoring are also shown.

U2 - 10.1021/acscatal.3c05378

DO - 10.1021/acscatal.3c05378

M3 - Article

C2 - 38269038

SN - 2155-5435

VL - 14

SP - 994

EP - 1004

JO - ACS Catalysis

JF - ACS Catalysis

IS - 2

ER -