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The reaction of an iridium PNP complex with parahydrogen facilitates polarisation transfer without chemical change.

Holmes AJ, Rayner PJ, Cowley MJ, Green GG, Whitwood AC, Duckett SB - Dalton Trans (2015)

Bottom Line: The short lived pincer complex [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(py)]BF4 is shown to be active for signal amplification by reversible exchange.When the catalysts (1)H nuclei are replaced by (2)H, increased levels of substrate hyperpolarization result and when the reverse situation is examined the catalyst itself is clearly visible through hyperpolarised signals.The ligand exchange pathways of [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(py)]BF4 that are associated with this process are shown to involve the formation of 16-electron [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2]BF4 and the 18-electron H2 addition product [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(H2)]BF4.

View Article: PubMed Central - PubMed

Affiliation: Centre for Hyperpolarization in Magnetic Resonance, University of York, York Science Park, York, YO10 5NY, UK. simon.duckett@york.ac.uk.

ABSTRACT
The short lived pincer complex [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(py)]BF4 is shown to be active for signal amplification by reversible exchange. This catalyst formulation enables the efficient transfer of polarization from parahydrogen to be placed into just a single molecule of the hyperpolarisation target, pyridine. When the catalysts (1)H nuclei are replaced by (2)H, increased levels of substrate hyperpolarization result and when the reverse situation is examined the catalyst itself is clearly visible through hyperpolarised signals. The ligand exchange pathways of [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(py)]BF4 that are associated with this process are shown to involve the formation of 16-electron [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2]BF4 and the 18-electron H2 addition product [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(H2)]BF4.

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Reaction of [(C5H3N(CH2P(tBu)2)2)IrH(C8H11)(NCCH3)]BF4 (1) with H2 forms the indicated cis-dihydride complex.18
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sch1: Reaction of [(C5H3N(CH2P(tBu)2)2)IrH(C8H11)(NCCH3)]BF4 (1) with H2 forms the indicated cis-dihydride complex.18

Mentions: In this study we utilize the reaction of 2,6-bis(di-tert-butylphosphinomethyl)-pyridine with [IrCl(COD)2]BF4 (COD = cyclooctadiene) to prepare the known PNP pincer16,17 complex [(C5H3N(CH2P(tBu)2)2)IrH(C8H11)(NCCH3)]BF4 (1)18 (Scheme 1) and then explore its potential to act as a catalyst for signal amplification by reversible exchange (SABRE).19 This process involves the catalytic transfer of magnetism from p-H2 into what has been established to be a wide array of ligands which bind reversibly to transition metal centres.20–23 Subsequent equilibration of the metal-bound ligand with other molecules in bulk solution leads to the build up of these materials as hyperpolarised, and yet chemically unmodified, spin-probes that can be readily detected by NMR or MRI.20,24,25 The use of pincer complexes by Shaw26 has led to the development of many ligand systems,27 coupled with an array of novel reaction outcomes28,29 that include both the reduction of CO2 30 and alkane dehydrogenation.31,32 Here we explore the fact that three metal coordination sites can be blocked by a pincer to improve the specificity of the SABRE hyperpolarisation transfer process. This has required the preparation of related 2H labelled derivatives.


The reaction of an iridium PNP complex with parahydrogen facilitates polarisation transfer without chemical change.

Holmes AJ, Rayner PJ, Cowley MJ, Green GG, Whitwood AC, Duckett SB - Dalton Trans (2015)

Reaction of [(C5H3N(CH2P(tBu)2)2)IrH(C8H11)(NCCH3)]BF4 (1) with H2 forms the indicated cis-dihydride complex.18
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4295814&req=5

sch1: Reaction of [(C5H3N(CH2P(tBu)2)2)IrH(C8H11)(NCCH3)]BF4 (1) with H2 forms the indicated cis-dihydride complex.18
Mentions: In this study we utilize the reaction of 2,6-bis(di-tert-butylphosphinomethyl)-pyridine with [IrCl(COD)2]BF4 (COD = cyclooctadiene) to prepare the known PNP pincer16,17 complex [(C5H3N(CH2P(tBu)2)2)IrH(C8H11)(NCCH3)]BF4 (1)18 (Scheme 1) and then explore its potential to act as a catalyst for signal amplification by reversible exchange (SABRE).19 This process involves the catalytic transfer of magnetism from p-H2 into what has been established to be a wide array of ligands which bind reversibly to transition metal centres.20–23 Subsequent equilibration of the metal-bound ligand with other molecules in bulk solution leads to the build up of these materials as hyperpolarised, and yet chemically unmodified, spin-probes that can be readily detected by NMR or MRI.20,24,25 The use of pincer complexes by Shaw26 has led to the development of many ligand systems,27 coupled with an array of novel reaction outcomes28,29 that include both the reduction of CO2 30 and alkane dehydrogenation.31,32 Here we explore the fact that three metal coordination sites can be blocked by a pincer to improve the specificity of the SABRE hyperpolarisation transfer process. This has required the preparation of related 2H labelled derivatives.

Bottom Line: The short lived pincer complex [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(py)]BF4 is shown to be active for signal amplification by reversible exchange.When the catalysts (1)H nuclei are replaced by (2)H, increased levels of substrate hyperpolarization result and when the reverse situation is examined the catalyst itself is clearly visible through hyperpolarised signals.The ligand exchange pathways of [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(py)]BF4 that are associated with this process are shown to involve the formation of 16-electron [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2]BF4 and the 18-electron H2 addition product [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(H2)]BF4.

View Article: PubMed Central - PubMed

Affiliation: Centre for Hyperpolarization in Magnetic Resonance, University of York, York Science Park, York, YO10 5NY, UK. simon.duckett@york.ac.uk.

ABSTRACT
The short lived pincer complex [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(py)]BF4 is shown to be active for signal amplification by reversible exchange. This catalyst formulation enables the efficient transfer of polarization from parahydrogen to be placed into just a single molecule of the hyperpolarisation target, pyridine. When the catalysts (1)H nuclei are replaced by (2)H, increased levels of substrate hyperpolarization result and when the reverse situation is examined the catalyst itself is clearly visible through hyperpolarised signals. The ligand exchange pathways of [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(py)]BF4 that are associated with this process are shown to involve the formation of 16-electron [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2]BF4 and the 18-electron H2 addition product [(C5H3N(CH2P((t)Bu)2)2)Ir(H)2(H2)]BF4.

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