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.
Chemistry. 2013 Jan 28;19(5):1796-809. doi: 10.1002/chem.201202794. Epub 2012 Dec 18.
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.
双(乙烯)铱(I)配合物[Tp(Me(2))Ir(C(2)H(4))(2)]（1；Tp(Me(2))=氢三(3,5-二甲基吡唑基)硼酸盐）与两当量的芳香族或脂肪族醛在一当量的二甲基丙炔二羧酸酯（DMAD）存在下反应，最终形成式为[Tp(Me(2))Ir(H){C(R(1))=C(R(2))C(R(3))O}]（R(1)=R(2)=CO(2)Me；R(3)=烷基，芳基；3）的氢铱呋喃。在反应过程中观察到了几个中间体。提出的关键步骤是在未检测到的 Ir(I)物种[Tp(Me(2))Ir{η(1)-O-R(3)C(=O)H}(DMAD)]（A）中进行 C-C 偶联反应，生成三角双锥 16e(-)Ir(III)中间体[Tp(Me(2))Ir{C(CO(2)Me)=C(CO(2)Me)C(R(3))(H)O}]（C），这些中间体已被 NCMe 捕获，生成加合物 11（R(3)=Ar）。如果第二个醛作为这些物种的捕获试剂，该配体通过形成烷氧基基团，作为氢原子从 iridacycle 的γ-碳原子转移到α-碳原子的穿梭体。丙炔酸甲酯（MP）可代替 DMAD 进行区域选择性地得到相关的铱呋喃。这些反应也通过 DFT 计算进行了研究。
