In this work, we utilize ¹H benchtop nuclear magnetic resonance (NMR) spectroscopy (proton frequency 44.7 MHz) for real-time monitoring of spin-transfer catalysis, starting from an iridium-based organometallic precursor complex [Ir(IMes)(COD)-Cl] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, COD = cyclooctadiene) with hydrogen in solution. We identify two distinct activation pathways: first, via the formation of a neutral intermediate complex [Ir(IMes)(COD)(H)₂Cl], and second, via the formation of charged complexes [Ir+(IMes)(COD)(H)₂)R]Cl⁻ (with R being bound ligands: acetonitrile, ammonia, or benzylamine). We conclude that the pathway direction is dominated by solvent polarity and explore SABRE (Signal Amplification by Reversible Exchange) of an acetonitrile solvent in the presence of a benzylamine coligand. These results are important for a better understanding of chemical dynamics in SABRE systems as well as for the fundamental physics experiments that require stable and long-lasting polarization of highly concentrated molecules (e.g., those from the solvent itself).