Recent progress on NHC-stabilized early transition metal (group 3-7) complexes: Synthesis and applications

The present paper comprehensively reviews group 3-7 metal NHC complexes reported since 2014, with emphasis on their current applications and fundamental reactivity. Thanks to NHC stabilization, such metal complexes have witnessed significant and diversified developments, essentially in the area of homogeneous catalysis. Catalytic applications primarily include their use in unsaturated/polar monomer polymerization catalysis, hydro-elementation of C@O and C@N substrates, metathesis-based catalytic reactions, hydro-elementation of C@O substrates and oxidation reactions. Apart from additional stability, the use of NHC fine-tuned steric/electronic properties was demonstrated to be crucial for catalytic performances. NHC-bearing Group 6 and 7 complexes, which have been most studied recently, have also been exploited as luminescent molecules and for biomedical applications (as radiopharmaceutical and theranostic agents). The large pool of available NHCs should further promote developments and application of such metal complexes in future years. (C) 2020 Elsevier B.V. All rights reserved.