Coupling of Aromatic Aldehydes with CO<sub>2</sub>Me-Substituted Tp<sup>Me2</sup>Ir(III) Metallacyclopentadienes

Espinosa-Roa, Arián; Salazar, Verónica; López‐Serrano, Joaquín; Oñate, Enrique; Alvarado‐Rodríguez, José G.; Paneque, Margarita; Poveda, Manuel L.

doi:10.1021/om3000554

Cited by 19 publications

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“…As advanced above, this aquo complex can be obtained in very good yield by the reaction of [Tp Me2 Ir(C 6 H 5 ) 2 (N 2 )] ( 5 ) with 1 equiv of MeO 2 CCCCO 2 Me (DMAD) in water-saturated C 6 H 12 at 60 °C (Scheme ) . This species was completely characterized by NMR, and thus the phenylic and vinylic Ir-bonded carbon nuclei resonate at 142.3 and 146.3 ppm, respectively.…”

Section: Results and Discussionmentioning

confidence: 94%

Formation of β-Metallanaphthalenes by the Coupling of a Benzo-Iridacyclopentadiene with Olefins

et al. 2014

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We have synthesized a new type of metallaaromatic complexes, namely the hydride-β-iridanaphthalenes Tp Me2 Ir(H)[C(CH 2 R′)-C 6 H 4 -o-C(R)C(R)] (benzo-3-H,CH 2 R′), by reaction of the benzo-iridacyclopentadiene Tp Me2 Ir[C 6 H 4 -o-C(R)C(R)](OH 2 ) (benzo-1-OH 2 ) (Tp Me2 = hydrotris(3,5-dimethylpyrazolyl)borate, R = CO 2 Me) with olefins of the type CH 2 CHR′ (R′ = H, Me, C 6 H 4 -p-Me, OPh). These reactions are proposed to take place with the initial coordination of the olefin and isomerization to a carbene form and subsequent insertion into the Ir−C(phenylic) bond and a final α-H elimination. The reaction with ethoxyethylene does not afford the corresponding derivative but rather gives a mixture of three, isolable, compounds, which are proposed to derive from three different types of insertion of the olefin, one of them a typical 1,2-insertion and the other two as (different) carbenes. The related reactions of the iridacyclopentadiene Tp Me2 Ir[C(R) C(R)-C(R)C(R)](OH 2 ) (1-OH 2 ) are also discussed. For different combinations of precursor and olefin, we have observed differences in the regio-and stereochemistry of the insertions. ■ INTRODUCTIONMetalloaromatic species continue to attract the attention of both experimental 1 and theoretical chemists. 2 Since the first report in 1982 by Roper et al. of an osmabenzene, 3 several types of metallabenzenes have been reported. Many of them were obtained by serendipitous procedures, but several routes have been designed for the rational synthesis of derivatives of different metals, as for instance the reaction described by Haley et al., 4 which uses the C 5 precursor (Z)-3-(2-iodovinyl)-1,2-diphenylcyclopropene and has been applied to the synthesis of Ir and Pt metallabenzenes. Almost all of the metallabenzenes reported contain one or more substituents in the ring, in many cases as a consequence of the method of preparation or as a tool to provide stability to the metallaaromatic ring. 2c The simplest species, a parent metallabenzene without substituents on the C atoms of the aromatic ring, has been reported recently and was generated by the coupling in an iridium compound of two molecules of acetylene and a CH 2 fragment of a molecule of CH 2 Cl 2 , the solvent of the reaction. 5 Higher metallaaromatics such as metallanaphthalenes and metallaanthracenes are much less common. 6 For the case of metallanaphthalenes, to the best of our knowledge, only the three transition-metal complexes shown in Figure 1 have been described to date 7 and, as can be observed, in all of these cases the metal occupies the α-position of the aromatic ring. 8 The first derivative reported, the Tp Me2 -α-iridanaphthalene, 7a was generated by the mild oxidation of a bicyclic derivative (Scheme 1), for which also exists an analogue without the fused benzo ring, and it also transforms upon oxidation into a metalFigure 1. (a) The three known metallanaphthalenes. 7 (b) The structures of α-metallanaphthalenes (A) and β-metallanaphthalenes (B).Article pubs.acs.org/Organometallics

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Section: Results and Discussionmentioning

confidence: 94%

Formation of β-Metallanaphthalenes by the Coupling of a Benzo-Iridacyclopentadiene with Olefins

et al. 2014

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“…The appearance of a new peak at 9.4 ppm provides further evidence that aldehyde is possibly formed in the system, because the standard chemical shifts of the aldehyde proton usually appeared between 9 and 10 ppm. 47,48 It is well known that the oxidation potential of EG is 1.65 V at 25 °C and decreases as the temperature increases, indicating that the EG is a better reducing agent at elevated temperatures. 46,49 However, silver ion is hard to be reduced fast by EG at room temperature, which needs several hours.…”

Section: Resultsmentioning

confidence: 99%

Ultrafine silver nanoparticles obtained from ethylene glycol at room temperature: catalyzed by tungstate ions

Zhu

Liu

2014

Dalton Trans.

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Ethylene glycol (EG) has been widely utilized to fabricate silver nanoparticles with uniform size and morphology. However, the majority of the work reported to date using EG routinely require not only heating, but also a surfactant. In the present paper, we report a surfactant-free and facile method for the synthesis of fairly monodisperse smaller silver nanoparticles (~6 nm) through the reaction of silver ions with EG by using tungstates (such as potassium tungstate, sodium tungstate) as catalysts at room temperature. Particularly, in this method, tungstates as catalysts can dramatically speed up the reduction of silver ions, and EG acts as both a solvent and a reducing agent to reduce silver ions to Ag metal. Meantime, we have carried out a series of experiments to investigate the performance of the as-prepared silver nanoparticles. It was found that the silver nanoparticles show excellent catalytic activity for the reduction of 4-nitrophenol in the presence of NaBH4.

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“…Thus, although compound 7a is made up formally from two molecules of DMAD and one of anisaldehyde, it has to be obtained by following strictly the procedure described herein. In fact, if 2 equiv of DMAD is added first to compound 1 , the substitution of the two ethylenes is kinetically very favorable, and the iridacyclopentadiene fragment [Tp Me2 r(−C(R)C(R)–C(R)C(R))] is formed. , Addition of aldehyde to this species gives rise to a different product, a bicyclic isomer of 7 with a different functionality derived from the aldehyde moiety: a carbene instead of a keto group, with an unexpected configuration of the carbon atom of the Ir–CHR moiety (Scheme ) …”

Section: Resultsmentioning

confidence: 99%

“…), 112.0 (C 2 ), 108. 8,108.5,107.3 (CHpz), 50.0, 49.6 (CO2Me), 17.7 (C 1 , 1 JCH = 132 Hz), 14.8, 13.9, 13.1, 12.6, 12.6, 12. Synthesis of compound 6a. Complex 2a (0.15 g, 0.19 mmol) was dissolved in dichloromethane (7 mL) and the solution placed in a Fisher-Porter vessel which was pressurized with C2H4 (3 atm).…”

Section: Methodsmentioning

confidence: 99%

“…4,7 Addition of aldehyde to this species gives rise to a different product, 8 a bicyclic isomer of 7 with a different functionality derived from the aldehyde moiety: a carbene instead of a keto group, with an unexpected configuration of the carbon atom of the Ir−CHR moiety (Scheme 7). 8 As noted before, the formation of compounds 2a,b requires the use of 2 equiv of aldehyde, with one of them recovered at the end of the reaction. Therefore, purification of these complexes normally requires silica gel column chromatography, although we have now found that, for the case of 2a, a simple washing of the crude product with several portions of cold hexane removes the excess aldehyde and gives the iridafuran in pure form (90% yield vs 75% following chromatography).…”

Section: ■ Introductionmentioning

confidence: 94%

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Reactivity of Tp^Me2-Containing Hydride–Iridafurans with Alkenes, Alkynes, and H₂

et al. 2014

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The Tp Me2 -containing hydride-iridafurans 2a,b (Tp Me2 = hydrotris(3,5dimethylpyrazolyl)borate) cleanly reacted with ethylene to give the bicyclic derivatives 6a,b. Formation of the latter complexes is a reversible process and it is proposed to occur by an electrocyclic ring closure that takes place between C2H4 and the 16eunsaturated intermediates A resulting from hydride migration to the -carbon of the metallacycle. Similar reactions were observed with a variety of alkynes RCCR (R = H, Ph, CO2Me) and R´CCH (R´= CO2Me, Ph, CMe3) with the regioselectivity observed for the latter substrates depending on the nature of R´. In the case of Me3SiCCH the structure of an 2 unexpected byproduct indicates that an alkyne-vinylidene rearrangement has taken place on the metal coordination sphere during the reaction and this observation suggests that in the mechanism of all these coupling processes the corresponding -adducts are active intermediates. Finally, complexes 2a,b reacted with H2 to give products derived from the hydrogenation of their alkenyl arms.

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Coupling of Aromatic Aldehydes with CO₂Me-Substituted Tp^Me2Ir(III) Metallacyclopentadienes

Cited by 19 publications

References 48 publications

Formation of β-Metallanaphthalenes by the Coupling of a Benzo-Iridacyclopentadiene with Olefins

Formation of β-Metallanaphthalenes by the Coupling of a Benzo-Iridacyclopentadiene with Olefins

Ultrafine silver nanoparticles obtained from ethylene glycol at room temperature: catalyzed by tungstate ions

Reactivity of Tp^Me2-Containing Hydride–Iridafurans with Alkenes, Alkynes, and H₂

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Coupling of Aromatic Aldehydes with CO2Me-Substituted TpMe2Ir(III) Metallacyclopentadienes

Cited by 19 publications

References 48 publications

Formation of β-Metallanaphthalenes by the Coupling of a Benzo-Iridacyclopentadiene with Olefins

Formation of β-Metallanaphthalenes by the Coupling of a Benzo-Iridacyclopentadiene with Olefins

Ultrafine silver nanoparticles obtained from ethylene glycol at room temperature: catalyzed by tungstate ions

Reactivity of TpMe2-Containing Hydride–Iridafurans with Alkenes, Alkynes, and H2

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Coupling of Aromatic Aldehydes with CO₂Me-Substituted Tp^Me2Ir(III) Metallacyclopentadienes

Reactivity of Tp^Me2-Containing Hydride–Iridafurans with Alkenes, Alkynes, and H₂