Indenylmetal Catalysis in Organic Synthesis

Abstract

Synthetic organic chemists have a long-standing appreciation for transition metal cyclopentadienyl complexes, of which many have been used as catalysts for organic transformations. Much less well known are the contributions of the benzo-fuzed relative of the cyclopentadienyl ligand, the indenyl ligand, whose unique properties have in many cases imparted differential reactivity in catalytic processes toward the synthesis of small molecules. In this review, we will present examples of indenylmetal complexes in catalysis and compare their reactivity to their cyclopentadienyl analogues, wherever possible.

Group 9 Metallacyclopentadienes as Key Intermediates in [2+2+2] Alkyne Cyclotrimerizations. Insight from Activation Strain Analyses

“…An extension to group 9 elements, in particular to Rh, was initially proposed by Booth et al [23] and Ingrosso et al [24] They used numerous different Rh(I) half-sandwich complexes to investigate how to trim and optimize selectivity and the overall cyclotrimerization yield. [10,25,26] The catalytic use of CpM fragments in acetylene [2 + 2 + 2] cyclotrimerization to benzene and alkyne/nitrile [2 + 2 + 2] cycloaddition to pyridine has been investigated also in silico for different metals: Co, [27,28] Rh, [10,29] Ir, [30,31] Ru. [10,25,26] The catalytic use of CpM fragments in acetylene [2 + 2 + 2] cyclotrimerization to benzene and alkyne/nitrile [2 + 2 + 2] cycloaddition to pyridine has been investigated also in silico for different metals: Co, [27,28] Rh, [10,29] Ir, [30,31] Ru.…”

Desulfurization of model and real fuels by extraction and oxidation processes using an indenylmolybdenum tricarbonyl pre‐catalyst

“…To achieve the best desulfurization results, some diesel samples were treated in advance by a liquid-liquid extraction (LLE) process using acetonitrile or dimethylformamide (DMF). The effect of applying an ECODS system to desulfurize untreated diesel samples was also tested, using the IL [BMIM]PF 6 .…”

“…For the extractant-free CODS and IL-containing ECODS systems, the highest desulfurization efficiencies were reached when an initial extraction was included in the ODS process together with a final extraction ( 6 have been shown to display selectivity for the removal (by extraction/absorption) of aromatic S-containing molecules over olefins and aromatic hydrocarbons from real liquid fuels, [42] the use of an IL as an extractant in an ODS process may help to prevent the oxidation of other diesel components that could cause a decrease in the desulfurization efficiency by competing with the desired oxidation of sulfur compounds.…”

“…The distinctive reactivity of indenylmetal compounds has led to their use as catalysts for some important organic transformations . Increased activity of indenylmetal catalysts has frequently been associated with the traditional explanation of the indenyl effect, i.e.…”

“…[5] The distinctive reactivity of indenylmetal compounds has led to their use as catalysts for some important organic transformations. [6,7] Increased activity of indenylmetal catalysts has frequently been associated with the traditional explanation of the indenyl effect, i.e. a change in hapticity along the reaction coordinate, which is likely to be operative when substrate coordination to the metal center is a key step of the reaction mechanism.…”