Effects of a Tridentate Pincer Ligand on Parahydrogen Induced Polarization

Safiyah R. Muhammad; Joseph W. Nugent; Rianna B. Greer; Brian C. Lee; Jumanah Mahmoud; Steven B. Ramirez; Boyd M. Goodson; Alison R. Fout

doi:10.1002/cphc.202100178

Effects of a Tridentate Pincer Ligand on Parahydrogen Induced Polarization

Safiyah R. Muhammad, Joseph W. Nugent, Rianna B. Greer, Brian C. Lee, Jumanah Mahmoud, Steven B. Ramirez, Boyd M. Goodson, Alison R. Fout

Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

The role of ligands in rhodium- and iridium-catalyzed Parahydrogen Induced Polarization (PHIP) and SABRE (signal amplification by reversible exchange) chemistry has been studied in the benchmark systems, [Rh(diene)(diphos)]⁺ and [Ir(NHC)(sub)₃(H)₂]⁺, and shown to have a great impact on the degree of hyperpolarization observed. Here, we examine the role of the flanking moieties in the electron-rich monoanionic bis(carbene) aryl pincer ligand, ^ArCCC (Ar=Dipp, 2,6-diisopropyl or Mes, 2,4,6-trimethylphenyl) on the cobalt-catalyzed PHIP and PHIP-IE (PHIP via Insertion and Elimination) chemistry that we have previously reported. The mesityl groups were exchanged for diisopropylphenyl groups to generate the (^DippCCC)Co(N₂) catalyst, which resulted in faster hydrogenation and up to 390-fold ¹H signal enhancements, larger than that of the (^MesCCC)Co-py (py=pyridine) catalyst. Additionally, the synthesis of the (^DippCCC)Rh(N₂) complex is reported and applied towards the hydrogenation of ethyl acrylate with parahydrogen to generate modest signal enhancements of both ¹H and ¹³C nuclei. Lastly, the generation of two (^MesCCC)Ir complexes is presented and applied towards SABRE and PHIP-IE chemistry to only yield small ¹H signal enhancements of the partially hydrogenated product (PHIP) with no SABRE hyperpolarization.

Original language	English (US)
Pages (from-to)	1518-1526
Number of pages	9
Journal	ChemPhysChem
Volume	22
Issue number	14
DOIs	https://doi.org/10.1002/cphc.202100178
State	Published - Jul 16 2021

Keywords

PHIP
cobalt
iridium
parahydrogen
rhodium

ASJC Scopus subject areas

Atomic and Molecular Physics, and Optics
Physical and Theoretical Chemistry

Online availability

10.1002/cphc.202100178

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@article{4a8318a6545248b081de33bf48b425b3,

title = "Effects of a Tridentate Pincer Ligand on Parahydrogen Induced Polarization",

abstract = "The role of ligands in rhodium- and iridium-catalyzed Parahydrogen Induced Polarization (PHIP) and SABRE (signal amplification by reversible exchange) chemistry has been studied in the benchmark systems, [Rh(diene)(diphos)]+ and [Ir(NHC)(sub)3(H)2]+, and shown to have a great impact on the degree of hyperpolarization observed. Here, we examine the role of the flanking moieties in the electron-rich monoanionic bis(carbene) aryl pincer ligand, ArCCC (Ar=Dipp, 2,6-diisopropyl or Mes, 2,4,6-trimethylphenyl) on the cobalt-catalyzed PHIP and PHIP-IE (PHIP via Insertion and Elimination) chemistry that we have previously reported. The mesityl groups were exchanged for diisopropylphenyl groups to generate the (DippCCC)Co(N2) catalyst, which resulted in faster hydrogenation and up to 390-fold 1H signal enhancements, larger than that of the (MesCCC)Co-py (py=pyridine) catalyst. Additionally, the synthesis of the (DippCCC)Rh(N2) complex is reported and applied towards the hydrogenation of ethyl acrylate with parahydrogen to generate modest signal enhancements of both 1H and 13C nuclei. Lastly, the generation of two (MesCCC)Ir complexes is presented and applied towards SABRE and PHIP-IE chemistry to only yield small 1H signal enhancements of the partially hydrogenated product (PHIP) with no SABRE hyperpolarization.",

keywords = "PHIP, cobalt, iridium, parahydrogen, rhodium",

author = "Muhammad, {Safiyah R.} and Nugent, {Joseph W.} and Greer, {Rianna B.} and Lee, {Brian C.} and Jumanah Mahmoud and Ramirez, {Steven B.} and Goodson, {Boyd M.} and Fout, {Alison R.}",

note = "Publisher Copyright: {\textcopyright} 2021 Wiley-VCH GmbH.",

year = "2021",

month = jul,

day = "16",

doi = "10.1002/cphc.202100178",

language = "English (US)",

volume = "22",

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journal = "ChemPhysChem",

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T1 - Effects of a Tridentate Pincer Ligand on Parahydrogen Induced Polarization

AU - Muhammad, Safiyah R.

AU - Nugent, Joseph W.

AU - Greer, Rianna B.

AU - Lee, Brian C.

AU - Mahmoud, Jumanah

AU - Ramirez, Steven B.

AU - Goodson, Boyd M.

AU - Fout, Alison R.

PY - 2021/7/16

Y1 - 2021/7/16

N2 - The role of ligands in rhodium- and iridium-catalyzed Parahydrogen Induced Polarization (PHIP) and SABRE (signal amplification by reversible exchange) chemistry has been studied in the benchmark systems, [Rh(diene)(diphos)]+ and [Ir(NHC)(sub)3(H)2]+, and shown to have a great impact on the degree of hyperpolarization observed. Here, we examine the role of the flanking moieties in the electron-rich monoanionic bis(carbene) aryl pincer ligand, ArCCC (Ar=Dipp, 2,6-diisopropyl or Mes, 2,4,6-trimethylphenyl) on the cobalt-catalyzed PHIP and PHIP-IE (PHIP via Insertion and Elimination) chemistry that we have previously reported. The mesityl groups were exchanged for diisopropylphenyl groups to generate the (DippCCC)Co(N2) catalyst, which resulted in faster hydrogenation and up to 390-fold 1H signal enhancements, larger than that of the (MesCCC)Co-py (py=pyridine) catalyst. Additionally, the synthesis of the (DippCCC)Rh(N2) complex is reported and applied towards the hydrogenation of ethyl acrylate with parahydrogen to generate modest signal enhancements of both 1H and 13C nuclei. Lastly, the generation of two (MesCCC)Ir complexes is presented and applied towards SABRE and PHIP-IE chemistry to only yield small 1H signal enhancements of the partially hydrogenated product (PHIP) with no SABRE hyperpolarization.

AB - The role of ligands in rhodium- and iridium-catalyzed Parahydrogen Induced Polarization (PHIP) and SABRE (signal amplification by reversible exchange) chemistry has been studied in the benchmark systems, [Rh(diene)(diphos)]+ and [Ir(NHC)(sub)3(H)2]+, and shown to have a great impact on the degree of hyperpolarization observed. Here, we examine the role of the flanking moieties in the electron-rich monoanionic bis(carbene) aryl pincer ligand, ArCCC (Ar=Dipp, 2,6-diisopropyl or Mes, 2,4,6-trimethylphenyl) on the cobalt-catalyzed PHIP and PHIP-IE (PHIP via Insertion and Elimination) chemistry that we have previously reported. The mesityl groups were exchanged for diisopropylphenyl groups to generate the (DippCCC)Co(N2) catalyst, which resulted in faster hydrogenation and up to 390-fold 1H signal enhancements, larger than that of the (MesCCC)Co-py (py=pyridine) catalyst. Additionally, the synthesis of the (DippCCC)Rh(N2) complex is reported and applied towards the hydrogenation of ethyl acrylate with parahydrogen to generate modest signal enhancements of both 1H and 13C nuclei. Lastly, the generation of two (MesCCC)Ir complexes is presented and applied towards SABRE and PHIP-IE chemistry to only yield small 1H signal enhancements of the partially hydrogenated product (PHIP) with no SABRE hyperpolarization.

KW - PHIP

KW - cobalt

KW - iridium

KW - parahydrogen

KW - rhodium

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U2 - 10.1002/cphc.202100178

DO - 10.1002/cphc.202100178

M3 - Article

C2 - 34043874

AN - SCOPUS:85108140160

SN - 1439-4235

VL - 22

SP - 1518

EP - 1526

JO - ChemPhysChem

JF - ChemPhysChem

IS - 14

ER -

Effects of a Tridentate Pincer Ligand on Parahydrogen Induced Polarization

Abstract

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