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Abstract Demonstration of parahydrogen‐induced polarization effects in hydrogenations catalyzed by heterogeneous catalysts instead of metal complexes in a homogeneous solution has opened an entirely new dimension for parahydrogen‐based research, demonstrating its applicability not only for the production of catalyst‐free hyperpolarized liquids and gases and long‐lived non‐equilibrium spin states for potential biomedical applications, but also for addressing challenges of modern fundamental and industrial catalysis including advanced mechanistic studies of catalytic reactions and operando NMR and MRI of reactors. This essay summarizes the progress achieved in this field by highlighting the research contributed to it by our colleague and friend Kirill V. Kovtunov whose scientific career ended unexpectedly and tragically at the age of 37. His role in this research was certainly crucial, further enhanced by a vast network of his contacts and collaborations at the national and international level. 

Abstract The role of ligands in rhodium‐ and iridium‐catalyzedParahydrogen 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‐fold¹H 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 withparahydrogen to generate modest signal enhancements of both¹H and¹³C nuclei. Lastly, the generation of two (^MesCCC)Ir complexes is presented and applied towards SABRE and PHIP‐IE chemistry to only yield small¹H signal enhancements of the partially hydrogenated product (PHIP) with no SABRE hyperpolarization. 

Abstract Signal Amplification By Reversible Exchange in SHield Enabled Alignment Transfer (SABRE‐SHEATH) is investigated to achieve rapid hyperpolarization of¹³C₁spins of [1‐¹³C]pyruvate, using parahydrogen as the source of nuclear spin order. Pyruvate exchange with an iridium polarization transfer complex can be modulated via a sensitive interplay between temperature and co‐ligation of DMSO and H₂O. Order‐unity¹³C (>50 %) polarization of catalyst‐bound [1‐¹³C]pyruvate is achieved in less than 30 s by restricting the chemical exchange of [1‐¹³C]pyruvate at lower temperatures. On the catalyst bound pyruvate, 39 % polarization is measured using a 1.4 T NMR spectrometer, and extrapolated to >50 % at the end of build‐up in situ. The highest measured polarization of a 30‐mM pyruvate sample, including free and bound pyruvate is 13 % when using 20 mM DMSO and 0.5 M water in CD₃OD. Efficient¹³C polarization is also enabled by favorable relaxation dynamics in sub‐microtesla magnetic fields, as indicated by fast polarization buildup rates compared to theT₁spin‐relaxation rates (e. g., ∼0.2 s⁻¹versus ∼0.1 s⁻¹, respectively, for a 6 mM catalyst‐[1‐¹³C]pyruvate sample). Finally, the catalyst‐bound hyperpolarized [1‐¹³C]pyruvate can be released rapidly by cycling the temperature and/or by optimizing the amount of water, paving the way to future biomedical applications of hyperpolarized [1‐¹³C]pyruvate produced via comparatively fast and simple SABRE‐SHEATH‐based approaches.