title: Aldehyde-assisted hydrogen transfer during the formation of hydride-iridafurans from alkynes and aldehydes.
abstract: The bis(ethylene) Ir(I) complex [Tp(Me(2))Ir(C(2)H(4))(2)] (1; Tp(Me(2))=hydrotris(3,5-dimethylpyrazolyl)borate) reacts with two equivalents of aromatic or aliphatic aldehydes in the presence of one equivalent of dimethyl acetylenedicarboxylate (DMAD) with ultimate formation of hydride iridafurans of the formula [Tp(Me(2))Ir(H){C(R(1))=C(R(2))C(R(3))O}] (R(1)=R(2)=CO(2) Me; R(3)=alkyl, aryl; 3). Several intermediates have been observed in the course of the reaction. It is proposed that the key step of metallacycle formation is a C-C coupling process in the undetected Ir(I) species [Tp(Me(2))Ir{η(1)-O-R(3)C(=O)H}(DMAD)] (A) to give the trigonal-bipyramidal 16e(-) Ir(III) intermediates [Tp(Me(2))Ir{C(CO(2)Me)=C(CO(2)Me)C(R(3))(H)O}] (C), which have been trapped by NCMe to afford the adducts 11 (R(3)=Ar). If a second aldehyde acts as the trapping reagent for these species, this ligand acts as a shuttle in transfering a hydrogen atom from the γ- to the α-carbon atom of the iridacycle through the formation of an alkoxide group. Methyl propiolate (MP) can be used instead of DMAD to regioselectively afford the related iridafurans. These reactions have also been studied by DFT calculations.
authors.affiliation: Instituto de Investigaciones Químicas (IIQ) and Departamento de Química Inorgánica, Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Av. Américo Vespucio 49, Isla de la Cartuja, 41092 Sevilla, Spain.
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Posadas
authors.forename: Nuria
authors.initials: N
authors.lastname: Rendón
authors.forename: Joaquín
authors.initials: J
authors.lastname: López-Serrano
authors.forename: Yohar A
authors.initials: YA
authors.lastname: Hernández
authors.forename: Eleuterio
authors.initials: E
authors.lastname: Álvarez
authors.forename: Margarita
authors.initials: M
authors.lastname: Paneque
authors.forename: Manuel L
authors.initials: ML
authors.lastname: Poveda