title: Mechanism of hydrogenolysis of an iridium-methyl bond: evidence for a methane complex intermediate.
abstract: Evidence for key σ-complex intermediates in the hydrogenolysis of the iridium-methyl bond of (PONOP)Ir(H)(Me)(+) (1) [PONOP = 2,6-bis(di-tert-butylphosphinito)pyridine] has been obtained. The initially formed η(2)-H(2) complex, 2, was directly observed upon treatment of 1 with H(2), and evidence for reversible formation of a σ-methane complex, 5, was obtained through deuterium scrambling from η(2)-D(2) in 2-d(2) into the methyl group of 2 prior to methane loss. This sequence of reactions was modeled by density functional theory calculations. The transition state for formation of 5 from 2 showed significant shortening of the Ir-H bond for the hydrogen being transferred; no true Ir(V) trihydride intermediate could be located. Barriers to methane loss from 2 were compared to those of 1 and the six-coordinate species (PONOP)Ir(H)(Me)(CO)(+) and (PONOP)Ir(H)(Me)(Cl).
authors: Departamento de Química Inorgánica, Instituto de Investigaciones Químicas (IIQ), Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Avda. Américo Vespucio 49, 41092 Sevilla, Spain.
authors: Jesús
authors: J
authors: Campos
authors: Sabuj
authors: S
authors: Kundu
authors: Dale R
authors: DR
authors: Pahls
authors: Maurice
authors: M
authors: Brookhart
authors: Ernesto
authors: E
authors: Carmona
authors: Thomas R
authors: TR
authors: Cundari
mesh_terms: D006859:Hydrogen / Q000737:chemistry*; D006865:Hydrogenation; D007495:Iridium / Q000737:chemistry*; D008697:Methane / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D009942:Organometallic Compounds; D007495:Iridium; D006859:Hydrogen; D008697:Methane