Flash Communication: Probing Fe Complex Assembly via Thermogravimetric Analysis

First-row transition metal catalysis continues to provide innovative and sustainable advances for synthetic chemistry. However, these metals can be challenging to screen efficiently in optimization campaigns due to the limited knowledge of catalyst assembly, stability, and speciation. In this report we demonstrate the use of thermogravimetric analysis (TGA) as a promising tool in evaluating the formation and properties of an Fe precatalyst, <i>fac</i>-Fe-(dpa)-Cl₃. Using TGA it was possible to identify the generation of distinct Fe complexes that could form <i>in situ</i> from prestirring the commercial metal salt iron trichloride (FeCl₃) and di-(2-picolyl)-amine (dpa) in different organic solvents. Upon applying these prestirred mixtures to the reaction between methionine and benzyl acrylate, it was determined that distinct complexes gave distinct TGA profiles. Similar TGA profiles yielded similar reaction yields, while distinct TGA profiles tended to give rise to unique yields. Utilizing this approach, a more informed first-row metal catalyzed reaction strategy can be realized.