Catalytic Azoarene Synthesis from Aryl Azides Enabled by a Dinuclear Ni Complex

Powers, Ian G.; Andjaba, John M.; Luo, Xuyi; Mei, Jianguo; Uyeda, Christopher

doi:10.1021/jacs.8b00503

Cited by 68 publications

(54 citation statements)

References 102 publications

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“…[7][8][9] Indeed, sterically accessible multimetallic cores can support a wide variety of binding modes, including bridging ones that may enable reactivity not observed in monometallic systems. 10,11 Unsaturated substrates such as alkenes, alkynes, and nitriles, provide interesting cases as they can interact in an end-on (h 1 ) or side-on (h 2 ) fashion with each metal center ( Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex

et al. 2020

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“…The Cr 2 L 2 moiety here is more reducing towards azobenzene than is ab imetallic nickelc omplex where two reduced nickel centers are effective in reducing azobenzene N-(1.378(3) ), but not cleaving the N=Nb ond. [10] In our earliest work, we failed to appreciate that Cr III ,i na dducts between [CrL] 2 and azobenzene, is so unsaturated that it abstracts nucleophiles from oven-dried glassware. The products of azobenzene reaction in untreated glassware, [Cr 3…”

Section: Reaction Of [Crl] 2 With Azobenzenementioning

confidence: 99%

A Dimeric Chromium(II) Pincer as an Electron Shuttle for N=N Bond Scission

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Caulton

2020

Chemistry A European J

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Reduction of the bis-pyrazolyl pyridine complex [CrL] 2 with 4KC 8 ,f ollowed by addition of one azobenzene (overall mole ratio 1:4:1), PhNNPh, transfers reducing equivalents to three azobenzenes, to form [K 3 Cr(PhNNPh) 3 ]. This has three k 2 PhNNPh 2À ligands and K + bound to nitrogen atoms of azobenzene. When the stoichiometry is modified to 1:4:3, the product is changed to [K 2 CrL(PhNNPh) 2 ], which has C 2 symmetry except for the intimate ion pairingo ft wo K + ions to reduceda zobenzene nitrogen atoms, andt op yrazolate and phenylr ings. The origin of the observed delivery of reducinge quivalents to several, not to as ingle N=N bond, is traced to the resistance of the one-electron-reduced substrate to receiving as econd electron, and is thus ag eneral phenomenon. [CrL] 2 alone is shown to be atwo-electron reductant towards benzo[c]cinnoline (BCC) resulting in a product of formula [Cr 2 L 2 (BCC)],i nw hich the reducing equivalents originate purely from Cr II .A na nalogous study of the reaction of [CrL] 2 with azobenzene yields [Cr 2 L 2 (PhNNPh)(THF)],a na dduct in whicho ne THF has displaced one of four hydrazide nitrogen/Cr bonds.T ogether these illustrate different modes for the Cr 2 L 2 unit to bind and reduce the N=Nb ond. Collectively,t heser esultss how that two divalentC r, without added K 0 ,h avet he ability to reduce the N=Nb ond. Further KC 8 reduction of preformed Cr 2 L 2 (RNNR) inevitably gives products in which K + stabilizes the charge in the increasingly electron-rich nitrogena toms, in ap henomenonw hich mimics proton coupled electron transfer:K + performs the role of H + .Aleast-squares fit of the two singlyr educed DFT structures shows that the only major change is ar e-orientationo fo ne of the two phenyl rings in ordert oa void repulsion with potassium but to still allow interaction of that phenyl p system with K + .T his shows both the impact of K + ,b eing modestt on itrogen/ chromium interactions, but nevertheless accommodating some p donation of phenyl to potassium. Finally,d elivering increasing equivalents of KC 8 leads to complete cleavage of the N=Nb ond, and both Nb ind to three Cr II .T he varied impacts of the K + electrophile on NN multiple bond reduction is discussed.

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“…Transition metals generally enable milder conditions for the formation of nitrenes and higher selectivity in their subsequent transfer. The majority of nitrene-transfer studies are focused on middle and late transition metals, which generally feature weaker metal-imido bonds and therefore exhibit more reactive nitrene functionalities [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In contrast, early transition metals (particularly chromium) typically exhibit less reactive nitrene functionalities due to the stability of multiple metal-nitrogen bonds [22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Chromium(II) Complexes with Chelating Bis(alkoxide) Ligand and Their Reactions with Organoazides and Diazoalkanes

et al. 2020

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Synthesis of new chromium(II) complexes with chelating bis(alkoxide) ligand [OO]Ph (H2[OO]Ph = [1,1′:4′,1′’-terphenyl]-2,2′’-diylbis(diphenylmethanol)) and their subsequent reactivity in the context of catalytic production of carbodiimides from azides and isocyanides are described. Two different Cr(II) complexes are obtained, as a function of the crystallization solvent: mononuclear Cr[OO]Ph(THF)2 (in toluene/THF, THF = tetrahydrofuran) and dinuclear Cr2([OO]Ph)2 (in CH2Cl2/THF). The electronic structure and bonding in Cr[OO]Ph(THF)2 were probed by density functional theory calculations. Isolated Cr2([OO]Ph)2 undergoes facile reaction with 4-MeC6H4N3, 4-MeOC6H4N3, or 3,5-Me2C6H3N3 to yield diamagnetic Cr(VI) bis(imido) complexes; a structure of Cr[OO]Ph(N(4-MeC6H4))2 was confirmed by X-ray crystallography. The reaction of Cr2([OO]Ph)2 with bulkier azides N3R (MesN3, AdN3) forms paramagnetic products, formulated as Cr[OO]Ph(NR). The attempted formation of a Cr–alkylidene complex (using N2CPh2) instead forms chromium(VI) bis(diphenylmethylenehydrazido) complex Cr[OO]Ph(NNCPh2)2. Catalytic formation of carbodiimides was investigated for the azide/isocyanide mixtures containing various aryl azides and isocyanides. The formation of carbodiimides was found to depend on the nature of organoazide: whereas bulky mesitylazide led to the formation of carbodiimides with all isocyanides, no carbodiimide formation was observed for 3,5-dimethylphenylazide or 4-methylphenylazide. Treatment of Cr2([OO]Ph)2 or H2[OO]Ph with NO+ leads to the formation of [1,2-b]-dihydroindenofluorene, likely obtained via carbocation-mediated cyclization of the ligand.

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Catalytic Azoarene Synthesis from Aryl Azides Enabled by a Dinuclear Ni Complex

Cited by 68 publications

References 102 publications

Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex

Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex

A Dimeric Chromium(II) Pincer as an Electron Shuttle for N=N Bond Scission

Synthesis of Chromium(II) Complexes with Chelating Bis(alkoxide) Ligand and Their Reactions with Organoazides and Diazoalkanes

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