Synthesis and C−C Coupling Reactivity of a Dinuclear Ni<sup>I</sup>−Ni<sup>I</sup> Complex Supported by a Terphenyl Diphosphine

Velian, Alexandra; Lin, Sibo; Miller, Alexander J. M.; Day, Michael; Agapie, Theodor

doi:10.1021/ja101699a

Cited by 139 publications

(88 citation statements)

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“…The 31 P NMR chemical shifts of the resulting species ( 2a , 41.0 ppm; 2b , 40.7 ppm) are similar to those reported for the p -terphenyl diphosphine supported Ni(0) (40.4 ppm). 23 Similarly, the protons assigned to the central arene resonate upfield compared with those of the free phosphine in the 1 H NMR spectrum of 2a–b , whereas the ether OC H 3 peak is only slightly shifted. These data are consistent with the formation of a Ni(0) species with interactions between the metal center and the aromatic π-system, but not the ether oxygen.…”

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confidence: 93%

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Nickel-Mediated Hydrogenolysis of C–O Bonds of Aryl Ethers: What Is the Source of the Hydrogen?

et al. 2012

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Mechanistic studies of the hydrogenolysis of aryl ethers by nickel were undertaken with (diphosphine)aryl methyl ethers. A Ni(0) complex containing Ni-arene interactions adjacent to the aryl-O bond was isolated. Heating led to aryl-O bond activation and generation of a nickel-aryl-methoxide complex. Formal β-H elimination from this species produced a nickel-aryl-hydride which can undergo reductive elimination in the presence of formaldehyde to generate a carbon monoxide adduct of Ni(0). The reported complexes map out a plausible mechanism of aryl ether hydrogenolysis catalyzed by nickel. Investigations of a previously reported catalytic system using isotopically labeled substrates are consistent with the mechanism proposed in the stoichiometric system, involving β-H elimination from a nickel alkoxide rather than cleavage of the Ni-O bond by H2.

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confidence: 93%

“…23,24 The m -terphenyl diphosphine motif was also found to predispose the metal center toward interaction with the carbon at the 2′-position of the central ring. 25 Toward exploiting potential C-X activation chemistry, ligand variants with ether substitution at this position were prepared.…”

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Nickel-Mediated Hydrogenolysis of C–O Bonds of Aryl Ethers: What Is the Source of the Hydrogen?

et al. 2012

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“…32 However, in another case demonstrated by Agapie et al, a para-terphenyl diphosphine ligand supporting bimetallic or monometallic complexes, the charge transfer from the first row transition metals to the middle phenyl ring can result in its dearomatization (Chart 1f). 33,34 This unusual phenomenon allowed unprecedented reactivity including the change of up to five oxidation states of a dinitrogen complex and four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site. 35 Our group has taken a different approach in order to achieve the goal of coordination flexibility and redox activity (Chart 1g, h).…”

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Reactivity and Properties of Metal Complexes Enabled by Flexible and Redox-Active Ligands with a Ferrocene Backbone

Huang

Diaconescu

2016

Inorg. Chem.

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Our group has focused on the organometallic chemistry of rare-earth metals and actinides for a decade. By installing ferrocene diamide ligands at electropositive metal centers, we have been able to disclose unprecedented reactivity toward aromatic N-heterocycles, arenes, and other small molecules such as P 4 . Systematic studies employing X-ray crystallography, spectroscopy, cyclic voltammetry, and DFT calculations revealed that the ferrocene backbone could stabilize the electron-deficient metal through a donor-acceptor type interaction. Most noteworthy is that this interaction can be readily turned on or off by the addition or removal of a Lewis base. In addition to its flexible coordination, the redox active nature of the ferrocene backbone enabled us to explore redox-switchable transformations. The introduction of ferrocene-based ligands into organolanthanide chemistry not only helped to study intriguing fundamental problems but also led to fruitful chemistry including small molecule activation and controlled co-polymerization reactions.3

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“…8 A Schlenk tube fitted with a Teflon stopper was charged with 2,5-diiodo-1,4-bis(methoxymethylether)hydroquinone (500 mg, 1.11 mmol, 1 equiv. ), 2-bromophenylboronic acid (468.6 mg, 2.33 mmol, 2.1 equiv.…”

Section: Synthesis Of 25-bis(2-bromophenyl)-14-(methoxymethylether)mentioning

confidence: 99%

Dioxygen Reduction by a Pd(0)–Hydroquinone Diphosphine Complex

Horak

Agapie

2016

J. Am. Chem. Soc.

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A novel p-terphenyl diphosphine ligand was synthesized with a noninnocent hydroquinone moiety as the central arene (1-H). Pseudo-tetrahedral 4-coordinate Ni0 and Pd0–quinone (2 and 3, respectively) complexes proved accessible by metalating 1-H with the corresponding M(OAc)2 precursors. O2 does not react with the Pd0–quinone species (3) and protonation occurs at the quinone moiety indicating that the coordinated oxidized quinonoid moiety prevents reactivity at the metal. A 2-coordinate Pd0–hydroquinone complex (4-H) was prepared using a one-pot metalation with PdII followed by reduction. The reduced quinonoid moiety in 4-H shows metal-coupled reactivity with small molecules. 4-H was capable of reducing a variety of substrates including dioxygen, nitric oxide, nitrous oxide, 1-azido adamantane, trimethylamine n-oxide, and 1,4-benzoquinone quantitatively producing 3 as the Pd-containing reaction product. Mechanistic investigations of dioxygen reduction revealed that the reaction proceeds through a η2-peroxo intermediate (Int1) at low temperatures followed by subsequent ligand oxidation at higher temperatures in a reaction that consumed half an equivalent of O2 and produced water as a final oxygenic byproduct. Control compounds with methyl protected phenolic moieties (4-Me), displaying a AgI center incapable of O2 binding (7-H) or a cationic Pd–H motif (6-H) allowed for the independent examination of potential reaction pathways. The reaction of 4-Me with dioxygen at low temperature produces a species (8-Me) analogous to Int1 demonstrating that initial dioxygen activation is an inner sphere Pd-based process where the hydroquinone moiety only subsequently participates in the reduction of O2, at higher temperatures, by H+/e– transfers.

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Synthesis and C−C Coupling Reactivity of a Dinuclear Ni^I−Ni^I Complex Supported by a Terphenyl Diphosphine

Cited by 139 publications

References 24 publications

Nickel-Mediated Hydrogenolysis of C–O Bonds of Aryl Ethers: What Is the Source of the Hydrogen?

Nickel-Mediated Hydrogenolysis of C–O Bonds of Aryl Ethers: What Is the Source of the Hydrogen?

Reactivity and Properties of Metal Complexes Enabled by Flexible and Redox-Active Ligands with a Ferrocene Backbone

Dioxygen Reduction by a Pd(0)–Hydroquinone Diphosphine Complex

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Synthesis and C−C Coupling Reactivity of a Dinuclear NiI−NiI Complex Supported by a Terphenyl Diphosphine

Cited by 139 publications

References 24 publications

Nickel-Mediated Hydrogenolysis of C–O Bonds of Aryl Ethers: What Is the Source of the Hydrogen?

Nickel-Mediated Hydrogenolysis of C–O Bonds of Aryl Ethers: What Is the Source of the Hydrogen?

Reactivity and Properties of Metal Complexes Enabled by Flexible and Redox-Active Ligands with a Ferrocene Backbone

Dioxygen Reduction by a Pd(0)–Hydroquinone Diphosphine Complex

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Synthesis and C−C Coupling Reactivity of a Dinuclear Ni^I−Ni^I Complex Supported by a Terphenyl Diphosphine