title: Dihydrogen catalysis of the reversible formation and cleavage of C-H and N-H bonds of aminopyridinate ligands bound to (η(5) -C5 Me5 )Ir(III.).
abstract: This study focuses on a series of cationic complexes of iridium that contain aminopyridinate (Ap) ligands bound to an (η(5) -C5 Me5 )Ir(III) fragment. The new complexes have the chemical composition [Ir(Ap)(η(5) -C5 Me5 )](+) , exist in the form of two isomers (1(+) and 2(+) ) and were isolated as salts of the BArF (-) anion (BArF =B[3,5-(CF3 )2 C6 H3 ]4 ). Four Ap ligands that differ in the nature of their bulky aryl substituents at the amido nitrogen atom and pyridinic ring were employed. In the presence of H2 , the electrophilicity of the Ir(III) centre of these complexes allows for a reversible prototropic rearrangement that changes the nature and coordination mode of the aminopyridinate ligand between the well-known κ(2) -N,N'-bidentate binding in 1(+) and the unprecedented κ-N,η(3) -pseudo-allyl-coordination mode in isomers 2(+) through activation of a benzylic C-H bond and formal proton transfer to the amido nitrogen atom. Experimental and computational studies evidence that the overall rearrangement, which entails reversible formation and cleavage of H-H, C-H and N-H bonds, is catalysed by dihydrogen under homogeneous conditions.
authors.affiliation: Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Av. Américo Vespucio 49, Isla de la Cartuja, 41092 Sevilla (Spain), Fax: (+34) 954460565.
authors.forename: Ana
authors.initials: A
authors.lastname: Zamorano
authors.forename: Nuria
authors.initials: N
authors.lastname: Rendón
authors.forename: Joaquín
authors.initials: J
authors.lastname: López-Serrano
authors.forename: José E V
authors.initials: JE
authors.lastname: Valpuesta
authors.forename: Eleuterio
authors.initials: E
authors.lastname: Álvarez
authors.forename: Ernesto
authors.initials: E
authors.lastname: Carmona
keywords: CH activation; NH activation; dihydrogen catalysis; iridium; ligand isomerisation