Iridium Organometallics

Peruzzini, Margherita; Bianchini, Claudio; Gonsalvi, Luca

doi:10.1016/b0-08-045047-4/00098-4

“…Olefin complexes are useful starting compounds in the iridium chemistry . In the search for information about the factors that control the competitive ruptures of C–H versus C–X with this element, we have studied the reactions of the known dimers [Ir(μ-Cl)(η 2 -C 8 H 14 ) 2 ] 2 ( 1 ) and [Ir(μ-Cl)(η 4 -C 8 H 12 )] 2 ( 2 ) with 2-(2-bromophenyl)pyridine.…”

Section: Introductionsupporting

confidence: 80%

Pyridyl-Directed C–H and C–Br Bond Activations Promoted by Dimer Iridium-Olefin Complexes

Boudreault

¹

,

Esteruelas

²

,

Mora

³

et al. 2018

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Complexes [Ir(μ-Cl)(η 2-C 8 H 14) 2 ] 2 (1) and [Ir(μ-Cl)(η 4-C 8 H 12)] 2 (2) promote the pyridyl-directed ortho-CH and ortho-CBr activations of the phenyl substituent of 2-(2-bromophenyl)pyridine. The formed products depend upon the olefin of the dimer, which governs the kinetic preference of the activation. The cyclooctene complex 1 reacts with the substituted heterocycle to give (η 2-C 8 H 14) 2 Ir(μ-Cl) 2 Ir{κ 2-C,N-[C 6 BrH 3-py]} 2 (3), in acetone, at room temperature. Treatment of 3 with K(acac) affords Ir(acac)(η 2-C 8 H 14) 2 (4) and Ir(acac){κ 2-C,N-[C 6 BrH 3-py]} 2 (5; acac = acetylacetone). Under more severe conditions, 2-ethoxyethanol under reflux, the reaction of 1 with the heterocycle gives a yellow solid, which yields a 5:82:7 mixture of 5, Ir(acac){κ 2-C,N-[C 6 BrH 3-py]}{κ 2-C,N-[C 6 H 4-py]} (6), and Ir(acac){κ 2-C,N-[C 6 H 4-py]} 2 (7) by reaction with K(acac). In acetone or toluene, at room temperature, 2-(2-bromophenyl)pyridine breaks the chloride bridges of dimer 2 to form IrCl(η 4-C 8 H 12){κ 1-N-[py-C 6 BrH 4 ]} (8), which evolves into IrClBr{κ 2-C,N-[C 6 H 4-py]}(η 4-C 8 H 12) (9) as a result of the oxidative addition of the ortho-CBr of the phenyl substituent to the metal center. Treatment of 9 with Ag 2 O in acetylacetone leads to Ir(acac){κ 2-C,N-[C 6 H 4-py]}{κ 1-C, η 2-[C 8 H 12-(C 3-acac)]} (10), as a consequence of the replacement of the halides by an O,O-chelate acac ligand and the outside to metal nucleophilic attack of a second acac group to the diene C−C double bond disposed trans to bromide.

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“…The unsaturated character is favored by less basic metal centers. While an almost unlimited number of d 8 square-planar rhodium complexes are known with 16-valence electrons, the number of iridium compounds of this type is much lower . A nice example of this trend is shown by eq .…”

Section: Introductionmentioning

confidence: 98%

Square-Planar Alkylidyne–Osmium and Five-Coordinate Alkylidene–Osmium Complexes: Controlling the Transformation from Hydride-Alkylidyne to Alkylidene

Buil

¹

,

Cardo

²

,

Esteruelas

³

et al. 2016

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Square-planar alkylidyne and five-coordinate alkylidene mixed (i)Pr3P-Os-IPr (IPr = 1,3-bis(diisopropylphenyl)imidazolylidene) complexes have been discovered and characterized, and their formation has been rationalized. The cationic five-coordinate hydride-alkylidyne compounds [OsHX(≡CPh)(IPr)(P(i)Pr3)]OTf (X = Cl (1), F (4); OTf = CF3SO3) undergo deprotonation with KO(t)Bu to afford the trans-halide-alkylidyne square-planar derivatives OsX(≡CPh)(IPr)(P(i)Pr3) (X = Cl (2), F (5)). Oxidative addition of the C(sp)-H bond of phenylacetylene and methyl propiolate along the Cl-Os-CPh axis of 2 with the hydrogen atom directed to the alkylidyne leads to alkynyl-cis-hydride-alkylidyne intermediates, which rapidly evolve into the five-coordinate alkylidene complexes Os(C≡CR)Cl(═CHPh)(IPr)(P(i)Pr3) (R = Ph (6), CO2Me (7)) as a consequence of the migration of the hydride from the metal center to the Cα atom of the alkylidyne. Oxidative addition of the C(sp)-H bond of methyl propiolate along the X-Os-CPh axis of 2 and 5 with the hydrogen atom directed to the halide gives the alkynyl-trans-hydride-alkylidyne derivatives OsH(C≡CCO2Me)X(≡CPh)(IPr)(P(i)Pr3) (X = Cl (8), F (9)). Complex 8 evolves into 7. However, complex 9 containing the stronger π-donor fluoride is stable. The oxidative addition of HCl to 2 selectively yields the cis-hydride-alkylidyne compound OsHCl2(≡CPh)(IPr)(P(i)Pr3) (10), which is also stable.

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“…These unusual findings in the chemistry of pyridylimino-isoindolines prompted us to study the behavior of HBMePHI toward the dimers [M(μ-Cl)(η 4 -C 8 H 12 )] 2 (M = Rh ( 1 ), Ir ( 2 )) and [M(μ-OH)(η 4 -C 8 H 12 )] 2 (M = Rh ( 3 ), Ir ( 4 )), which are cornerstones in the development of rhodium 13 and iridium 14 organometallic chemistry. This paper reports the results of this study, including the formation of novel eight-membered heterodimetallacycles and C–N bond activations in the isoindoline core, some degradation pathways of the polydentate ligand in basic medium, and the catalytic ability of some of the new complexes in the acceptorless and base-free dehydrogenation of secondary alcohols.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Degradation of Rhodium and Iridium Diolefin Catalysts for the Acceptorless and Base-Free Dehydrogenation of Secondary Alcohols

Buil

¹

,

Collado

²

,

Esteruelas

³

et al. 2021

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Rhodium and iridium diolefin catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols have been prepared, and their degradation has been investigated, during the study of the reactivity of the dimers [M(μ-Cl)(η 4 -C 8 H 12 )] 2 (M = Rh ( 1 ), Ir ( 2 )) and [M(μ-OH)(η 4 -C 8 H 12 )] 2 (M = Rh ( 3 ), Ir ( 4 )) with 1,3-bis(6′-methyl-2′-pyridylimino)isoindoline (HBMePHI). Complex 1 reacts with HBMePHI, in dichloromethane, to afford equilibrium mixtures of 1 , the mononuclear derivative RhCl(η 4 -C 8 H 12 ){κ 1 - N py -(HBMePHI)} ( 5 ), and the binuclear species [RhCl(η 4 -C 8 H 12 )] 2 {μ- N py , N py -(HBMePHI)} ( 6 ). Under the same conditions, complex 2 affords the iridium counterparts IrCl(η 4 -C 8 H 12 ){κ 1 - N py -(HBMePHI)} ( 7 ) and [IrCl(η 4 -C 8 H 12 )] 2 {μ- N py , N py -(HBMePHI)} ( 8 ). In contrast to chloride, one of the hydroxide groups of 3 and 4 promotes the deprotonation of HBMePHI to give [M(η 4 -C 8 H 12 )] 2 (μ-OH){μ- N py , N iso -(BMePHI)} (M = Rh ( 9 ), Ir ( 10 )), which are efficient precatalysts for the acceptorless and base-free dehydrogenation of secondary alcohols. In the presence of KO t Bu, the [BMePHI] − ligand undergoes three different degradations: alcoholysis of an exocyclic isoindoline-N double bond, alcoholysis of a pyridyl-N bond, and opening of the five-membered ring of the isoindoline core.

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Iridium Organometallics

Cited by 13 publications

References 777 publications

Pyridyl-Directed C–H and C–Br Bond Activations Promoted by Dimer Iridium-Olefin Complexes

Pyridyl-Directed C–H and C–Br Bond Activations Promoted by Dimer Iridium-Olefin Complexes

Square-Planar Alkylidyne–Osmium and Five-Coordinate Alkylidene–Osmium Complexes: Controlling the Transformation from Hydride-Alkylidyne to Alkylidene

Preparation and Degradation of Rhodium and Iridium Diolefin Catalysts for the Acceptorless and Base-Free Dehydrogenation of Secondary Alcohols

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