Iridium: Organometallic Chemistry

Abstract

The organometallic chemistry of iridium is reviewed. The general classes of complexes of iridium containing iridium to carbon bonds are surveyed. The preparations of iridium olefin complexes, iridium arene complexes, iridium carbonyl complexes, iridium cyclopentadienyl complexes, and other types of complexes are covered along with the use of those classes of compounds in preparing other organometallic iridium species. In addition, three areas in which organoiridium compounds find particular application are specifically reviewed: catalysis utilizing organometallic compounds of iridium, carbon–hydrogen (CH) bond activation chemistry with iridium, and hydrodesulfurization (HDS) studies using iridium. References to other reviews, to monographs, and to the primary literature are provided in all cases.

Aryl Ether Cleavage by Group 9 and 10 Transition Metals: Stoichiometric Studies of Selectivity and Mechanism

“…In contrast to metalation of 1a with Rh, Ir does not show olefin substitution with phosphine at room temperature, probably due to the stronger metal–olefin interaction in the case of Ir. This reactivity is consistent with the literature; the reaction of phosphine and (Ir­(COD)­Cl) 2 under mild conditions typically results in dimer dissociation to afford four-coordinate monophosphine Ir­(COD)Cl species . Examples of the use of heat or hydrogenation to dissociate COD have been reported in the case of electron-deficient or bulky phosphines.…”

“…Examples of the use of heat or hydrogenation to dissociate COD have been reported in the case of electron-deficient or bulky phosphines. In contrast, the Rh analogues undergo substitution at room temperature in the absence of H 2 . ,, The faster reaction with (Ir­(COD)­Cl) 2 in comparison to (Ir­(COE) 2 Cl) 2 may be due to the smaller steric profile of one COD vs two COE ligands, although the COE adduct is typically more reactive than the chelating COD ligand …”

“…This reactivity is consistent with the literature; the reaction of phosphine and (Ir(COD)Cl) 2 under mild conditions typically results in dimer dissociation to afford four-coordinate monophosphine Ir(COD)Cl species. 25 Examples of the use of heat 26 or hydrogenation 27 to dissociate COD have been reported in the case of electron-deficient 26 or bulky 27 phosphines. In contrast, the Rh analogues undergo substitution at room temperature in the absence of H 2 .…”

“…6b,e,28 The faster reaction with (Ir(COD)Cl) 2 in comparison to (Ir(COE) 2 Cl) 2 may be due to the smaller steric profile of one COD vs two COE ligands, although the COE adduct is typically more reactive than the chelating COD ligand. 25 Compound 27a is stable in solution at room temperature for extended periods ( 1 H and 31 P NMR spectroscopy, ESI-MS) of time. However, heating a slurry of compound 27a at 135 °C in m-xylene for 63 h affords a new major species, 28a, in ca.…”