Extensive Studies on the Synthesis and Characterization of π-Arene Chromium Complexes and Their Performance in S_NAr...

We report an efficient synthesis of a series of new (η⁶-arene)Cr(CO)₃ complexes via ligand exchange strategy under thermal conditions using chromium hexacarbonyl and readily accessible arene feedstocks. We optimized the previously reported procedures and found that the high excess of arenes usually employed is not required to access the π-arene chromium complexes in high yields. Consequently, the revised procedure simplifies the purification of chromium tricarbonyl complexes bearing arenes with high boiling points. The reaction is amenable to provide (η⁶-arene)Cr(CO)₃ complexes decorated with various functional groups. Notably, the novel and already reported chromium complexes with missing spectroscopic characterization were fully characterized by nuclear magnetic resonance (NMR), infrared (IR) spectroscopies, and high-resolution mass spectrometry (HRMS). Besides, we report the structure of 20 chromium complexes characterized via X-ray crystallography. The potential application of these π-arene chromium complexes has also been exploited toward the selective construction of poly(hetero)aryls possessing a single chromium tricarbonyl unit through S_NAr and Suzuki-Miyaura cross-coupling reactions. This work is meant to be a practical guide for the synthesis of π-arene chromium complexes and to fill the gap in their spectroscopic characterization.