C–O and C–N Functionalization of Cationic, NCN-Type Pincer Complexes of Trivalent Nickel: Mechanism, Selectivity, and Kinetic Isotope Effect

Cloutier, Jean-Philippe; Rechignat, Lionel; Canac, Yves; Ess, Daniel H.; Zargarian, Davit

doi:10.1021/acs.inorgchem.8b03489

Cited by 10 publications

(3 citation statements)

References 42 publications

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“…We will also explore the potential reactivities of the cyclonickelated compounds described herein for oxidation-induced C–heteroatom functionalization reactions. These studies will draw inspiration from recently reported model systems based on NCN-type pincer-Ni III complexes that promote C–N, C–O, and C–halide bond formation reactions …”

Section: Discussionmentioning

confidence: 99%

C–H Nickelation of Naphthyl Phosphinites: Electronic and Steric Limitations, Regioselectivity, and Tandem C–P Functionalization

Mangin

Zargarian

2019

Organometallics

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This report describes the results of a study on the C–H nickelation of phosphinites derived from variously substituted 1- and 2-naphthols, as well as the C–P functionalization of the Ni-naphthyl moiety arising from the C–H cyclonickelation. Refluxing 4-X-1-naphthyl phosphinites (X = H, 1a; MeO, 1b; Cl, 1c) with {(i-PrCN)NiBr2} n and Et3N in acetonitrile gave the nickelacyclic complexes {(κP,κC-4-X-1-OP(i-Pr)2-naphth-2-yl)Ni(μ-Br)}2, 2a–c, resulting from cyclonickelation at the C2–H, whereas cyclonickelation of the 2-naphthyl phosphinite analogue 1e under the same conditions occurred at C3–H. Placing a Me substituent at the C3 position of a 2-naphthyl phosphinite (1f) led to a very sluggish nickelation at the C1–H position, whereas 2-ethyl-1-naphthyl phosphinite (1d) failed to nickelate at C8–H. H/D scrambling tests conducted on the deuterated analogue of 1a (1a-d 7 ) confirmed that nickelation occurs exclusively at C2. Similar tests conducted on deuterated analogues of alkyl-substituted 1- and 2-naphthyl phosphinites showed that no nickelation takes place at Csp3 –H sites of the alkyl substituents. In contrast, very facile C–H nickelation was observed with 2-allyl-1-naphthyl phosphinite 1g to give a product featuring a π-allyl-Ni moiety. A series of tests have shown that the nickelation of substrates 1a, 1e, and 1f can be accelerated dramatically at 120–160 °C. On the other hand, conducting the high temperature reaction of 1a in the absence of Et3N resulted in an unanticipated and interesting C–P functionalization of the C2–H site, thus generating a i-Pr2P-substituted bidentate phosphine-phosphinite. A similar tandem C–H nickelation/C–P(O) functionalization was also observed at the C8–H position of substrate 1d. The mechanisms of these functionalization reactions have been probed and outlined.

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Section: Discussionmentioning

confidence: 99%

C–H Nickelation of Naphthyl Phosphinites: Electronic and Steric Limitations, Regioselectivity, and Tandem C–P Functionalization

Mangin

Zargarian

2019

Organometallics

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“…Our long-standing interest in the synthesis and reactivities of high-valent Ni complexes , prompted us to use cyclic voltammetry (CV) to measure the one-electron oxidation potentials of the above-mentioned POC sp 3 N and POC sp 3 P complexes. The main objective of this exercise was to study the variations in redox potentials as a function of different structural features, and use any insight gleaned from such studies to prepare thermally stable high-valent derivatives.…”

Section: Resultsmentioning

confidence: 99%

A Wacker-Type Strategy for the Synthesis of Unsymmetrical POC_sp³E-Nickel Pincer Complexes

2020

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ECE-type pincer complexes have evolved into a diverse family of compounds possessing interesting structural/bonding features, reactivities, and practical applications. An important factor promoting the growth of pincer chemistry is the availability of versatile synthetic pathways that give access to ever-diverse pincer complexes. This report describes the synthesis of pincer–Ni complexes possessing the following features: a central Ni–Csp3 linkage, two different peripheral donor moieties, and two differently sized metallacycles. The synthetic methodology reported herein is based on the reactivity of a phosphinite derived from 2-vinylphenol. Stirring the substrate 2-CH2CHC6H4-OP(i-Pr)2, 1, with the NiII precursor {(i-PrCN)NiBr2} n and Et3N at room temperature gave the 6,5-POCsp3 PO-type pincer complex {κ O ,κ C ,κ P -2-[(i-Pr)2P(O)CH2 CH]-C6H4-OP(i-Pr)2}NiBr, 2. Conducting this reaction in the presence of an excess of 1 hinders the formation of 2, giving instead the nickellacyclopropane complex {κ C ,κ,κ P -2-[(2-CH2CHC6H4O)P(i-Pr)2 CHCH]-C6H4-OP(i-Pr)2}NiBr, 3, whereas introducing a second, stronger nucleophile into the reaction mixture leads to the formation of pincer complexes featuring rare 4-membered metallacycles. For instance, using HNR(R′) as nucleophile gave the 6,4-POCsp3 N-type pincer complexes {κ N ,κ C ,κ P -2-[R(R′)NCH2 CH]-C6H4-OP(i-Pr)2}NiBr (NR(R′) = N-morpholyl, 4; NPh(Et), 5; NH(i-Pr), 6; NH(Ph), 7; NH(Cy), 8; NH(t-Bu), 9), whereas using HPR2 as nucleophile led to the 6,4-POCsp3 P-type pincer complexes {κ P ,κ C ,κ P ′ -2-[R2 PCH2 CH]-C6H4-OP(i-Pr)2}NiBr (R = i-Pr, 10; iPh, 11). Single crystal diffraction studies have established the solid-state structures of complexes 2–11. All the pincer complexes reported here feature 6-membered metallacycles defined by the phosphinite moiety, while the phosphine-oxide moiety in 2 defines a 5-membered metallacycle and 4-membered metallacycles form by the coordination of the amine moieties in 4–9 and the phosphines in 10 and 11. Cyclic voltammetry measurements on complexes 2, 4–6, 10, and 11 have shown that these pincer–Ni complexes undergo facile one-electron oxidation.

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“…(b) Attempted oxidation of Ni(II)-TEMPOH complexes. Our long-standing interest in the synthesis and reactivities of high valent Ni complexes [56][57][58][59] prompted us to investigate the redox potential of the cyclometalated complexes under discussion. Cyclic voltammetry (CV) measurements of the η 1 -TEMPOH adducts prepared in the course of the study indicated that none supported reversible electrochemical oxidation: we observed in all cases essentially irreversible redox phenomena (Fig.…”

Section: Dalton Transactions Papermentioning

confidence: 99%

Reactions of cyclonickelated complexes with hydroxylamines and TEMPO˙: isolation of new TEMPOH adducts of Ni(ii) and their reactivities with nucleophiles and oxidants

Sarker,

Zargarian

2024

Dalton Trans.

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C–O and C–N Functionalization of Cationic, NCN-Type Pincer Complexes of Trivalent Nickel: Mechanism, Selectivity, and Kinetic Isotope Effect

Abstract: This report presents the synthesis of new mono-and dicationic NCN-Ni III complexes and describes their reactivities with protic substrates. (NCN is the pincer-type ligand k N , k C , k N-2,6-(CH2NMe2)2-C6H3.

Cited by 10 publications

References 42 publications

C–H Nickelation of Naphthyl Phosphinites: Electronic and Steric Limitations, Regioselectivity, and Tandem C–P Functionalization

C–H Nickelation of Naphthyl Phosphinites: Electronic and Steric Limitations, Regioselectivity, and Tandem C–P Functionalization

A Wacker-Type Strategy for the Synthesis of Unsymmetrical POC_sp³E-Nickel Pincer Complexes

Reactions of cyclonickelated complexes with hydroxylamines and TEMPO˙: isolation of new TEMPOH adducts of Ni(ii) and their reactivities with nucleophiles and oxidants

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C–O and C–N Functionalization of Cationic, NCN-Type Pincer Complexes of Trivalent Nickel: Mechanism, Selectivity, and Kinetic Isotope Effect

Abstract: This report presents the synthesis of new mono-and dicationic NCN-Ni III complexes and describes their reactivities with protic substrates. (NCN is the pincer-type ligand k N , k C , k N-2,6-(CH2NMe2)2-C6H3.

Cited by 10 publications

References 42 publications

C–H Nickelation of Naphthyl Phosphinites: Electronic and Steric Limitations, Regioselectivity, and Tandem C–P Functionalization

C–H Nickelation of Naphthyl Phosphinites: Electronic and Steric Limitations, Regioselectivity, and Tandem C–P Functionalization

A Wacker-Type Strategy for the Synthesis of Unsymmetrical POCsp3E-Nickel Pincer Complexes

Reactions of cyclonickelated complexes with hydroxylamines and TEMPO˙: isolation of new TEMPOH adducts of Ni(ii) and their reactivities with nucleophiles and oxidants

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A Wacker-Type Strategy for the Synthesis of Unsymmetrical POC_sp³E-Nickel Pincer Complexes