Synthesis, Structure, and Catalytic Activity of Cyclometalated Iridium Complexes with a Bidentate POC Ligand

Synthesis, characterization and catalytic activity of cyclometalated iridium complexes with a bidentate POC ligand is presented. Metalation of POC-H (di-tert-butyl(phenoxy)phosphane) with [Ir(COD)Cl]2 proceeded rapidly at room temperature and afforded mixture of (POC)(POC-H)IrHCl (1 a) and (POC)(COD)IrHCl (1 b), from which complexes (POC)(L)IrHCl where L=PPh3 (1 c), bipyridine (1 d) and [2,2 & PRIME;-bipyridine]-6,6 & PRIME;-diol (1 e) were prepared through ligand exchange. The compounds were tested in acceptorless dehydrogenation of 1-phenylethanol and transfer dehydrogenation of ethanol in a context of comparison with pincer counterparts (POCOP)IrHCl and (PCN)IrHCl. An attempt to prepare a dihydride complex from 1 e led to dimeric complex [(POC)(bipy-diol-)IrH]2 (3) that could explain the low activity of 1 e. DFT studies provided insight into POC-H vs POCOP-H metalation mechanism. Synthesis and characterization of cyclometalated iridium complexes (POC)(L)IrHCl with a bidentate POC ligand is presented. The catalytic activity of complexes (POC)(L)IrHCl in acceptorless dehydrogenation of 1-phenylethanol and transfer dehydrogenation of ethanol is discussed and compared to (POCOP)IrHCl and (PCN)IrHCl pincer complexes.image

Automated summary

This study presents the synthesis, characterization and catalytic activity of cyclometalated iridium complexes with a bidentate POC ligand. Metalation of POC-H with [Ir(COD)Cl]2 yielded a mixture of (POC)(POC-H)IrHCl and (POC)(COD)IrHCl, which were further converted to (POC)(L)IrHCl complexes through ligand exchange. The compounds were tested in acceptorless and transfer dehydrogenation reactions and compared with pincer complexes. A dimeric complex was obtained from one of the complexes, explaining its low activity. DFT studies shed light on the metalation mechanism.