Synthesis, characterization and reactivity of iridium pincer complexes

Abstract

Using the pincer-ligated iridium fragment [(RPOCOP)Ir] (RPOCOP=2,6-bis(di-tert-butyl-phosphonito)benzene or 2,6-bis(di-iso-propyl-phosphonito)benzene), a range of complexes with widely varying steric and electronic properties, have been synthesized and studied. The complexes include the novel Ir species (tBuPOCOP)Ir(L) (L=MeCN (2), pyridine (3), 2,4,6-triphenylphosphinine (11)), (iPrPOCOP)Ir(H)(Cl)(L) (L=PPh3 (7), PCy3 (8), 2,4,6-triphenylphosphinine (12)) and (iPrPOCOP)Ir(L) (L=PPh3 (9), PCy3 (10), 2,4,6-triphenylphosphinine (13)). Complex 4, (tBuPOCOP)Ir(PPh3), serves as a convenient source of the latent Ir(I), 14-electron species [(tBuPOCOP)Ir], and is susceptible to ligand exchange chemistry; reactions with MeCN and pyridine afford complexes 2 and 3, respectively. Complexes 11–13 represent rare examples of phosphinine-ligated iridium complexes and are the first examples of any pincer-supported metal complex exhibiting coordination to a phosphinine. The solid-state structure of 11 was determined by single crystal X-ray diffraction studies.