Synthesis of unsymmetrical 5,6-POCOP′-type pincer complexes of nickel(<scp>ii</scp>): impact of nickelacycle size on structures and spectroscopic properties

Salah, Abderrahmen; Corpet, Martin; Khan, Najm ul-Hassan; Zargarian, Davit; Spasyuk, Denis

doi:10.1039/c5nj00807g

Cited by 19 publications

(7 citation statements)

References 53 publications

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“…To access mononuclear POCOP pincer complexes of the type {2,6-(R 2 PO) 2 -R′ n -C 6 H 3– n }NiX (X = Cl, Br), several different synthetic protocols have been developed, one of which involves refluxing the POCOP pincer ligand with NiX 2 in toluene . The cyclometalation reaction may be improved by replacing NiX 2 with a more soluble Ni(II) source, adding a base to neutralize the byproduct HX, or using the combination of both strategies . Chloride complexes {2,6-(R 2 PO) 2 -R′ n -C 6 H 3– n }NiCl can alternatively be synthesized by simply heating a mixture of resorcinol (or a substituted resorcinol), R 2 PCl, and nickel powder, as demonstrated by the Zargarian group …”

Section: Resultsmentioning

confidence: 99%

Janus POCOP Pincer Complexes of Nickel

et al. 2018

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A phosphinite-based dinickel pincer complex, {2,3,5,6-( i Pr2PO)4C6}Ni2Cl2, is synthesized by heating a mixture of 1,2,4,5-tetrahydroxybenzene, i Pr2PCl, NiCl2, and Et3N at 150 °C in a microwave reactor or refluxing 1,2,4,5-( i Pr2PO)4C6H2 with NiCl2 and Et3N at 175–250 °C in a flask. Substitution of chlorides by hydrides (from LiAlH4 or LiEt3BH) and methyl groups (from MeLi) generates {2,3,5,6-( i Pr2PO)4C6}Ni2H2 and {2,3,5,6-( i Pr2PO)4C6}Ni2Me2, respectively. Protonation of the methyl complex with HCO2H gives {2,3,5,6-( i Pr2PO)4C6}Ni2(OCHO)2. Spectroscopic and crystallographic data of these Janus POCOP pincer complexes are compared to those of the analogous mononuclear complexes {2,6-( i Pr2PO)2C6H3}NiX (X = Cl, H, Me, and OCHO). The hydride complex {2,3,5,6-( i Pr2PO)4C6}Ni2H2 reacts with phenylacetylene and CO2 to give insertion products. It also catalyzes the reduction of CO2 with catecholborane (HBcat) to yield CH3OBcat and catBOBcat with a turnover frequency of 7.5 min–1. The stoichiometric and catalytic activities of {2,3,5,6-( i Pr2PO)4C6}Ni2H2 are compared to those of {2,6-( i Pr2PO)2C6H3}NiH.

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Section: Resultsmentioning

confidence: 99%

Janus POCOP Pincer Complexes of Nickel

et al. 2018

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“…For the alkyl, ÀOSiR, ÀCF 3 , ÀN 3 and hydride substituents, a more direct approach can be used by reacting Grignard reagents, Me 3 SiL (L¼ÀOK, ÀCF 3 , ÀN 3 ) and LiAlH 4 , respectively, directly with the nickel halide [60][61][62][63][64][65][66][67][68].…”

Section: Introductionmentioning

confidence: 99%

Recent Advances on the Chemistry of POCOP–Nickel Pincer Compounds

Asay

Morales‐Morales

2015

The Privileged Pincer-Metal Platform: Coordination Chemistry &Amp; Applications

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“…A search of the literature revealed that most cyclonickelated complexes accessible via C–H nickelation are stabilized by pincer-type ligands . Our experience with the facile C–H nickelation of POCOP-type pincer ligands featuring aryl and alkyl phosphinite donor moieties encouraged us to test the reactivities of substrates bearing a single phosphinite DG. Initial tests showed that alkyl phosphinites were insufficiently reactive, whereas aryl phosphinites underwent relatively facile C–H nickelation.…”

Section: Introductionmentioning

confidence: 99%

C–H Nickelation of Aryl Phosphinites: Mechanistic Aspects

Mangin

Zargarian

2019

Organometallics

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The present report describes the results of a combined experimental and computational study on the mechanism of aryl phosphinite cyclonickelation. The reaction of ArOP(i-Pr)2 with [(i-PrCN)NiBr2] n proceeds more readily in acetonitrile relative to toluene; this is because the greater nucleophilicity of acetonitrile toward Ni stabilizes a more reactive acetonitrile adduct bearing one phosphinite ligand (as opposed to two). A sufficiently strong external base such as Et3N serves to quench the HBr generated at the nickelation step, thus allowing isolation of the cyclonickelated species. However, nickelation tests conducted in the absence of external base revealed that D/H scrambling occurs at the ortho positions of C6D5OP(i-Pr)2, implying that the cyclonickelation proceeds independently of the base. Thus, the main role of the external base is to prevent protonation of the Ni–aryl moiety formed via C–H nickelation. Tests have also shown that nickelation rates are affected by the quantity of the base used: the presence of more than 1 equiv of Et3N generates the less reactive biphosphinite complex trans-{PhOP(i-Pr)2}2NiBr2, thus inhibiting the desired C–H nickelation. Experimental studies have shown that nickelation is faster with aryl phosphinites bearing electron-donating substituents (Hammett slope ρ ≈ −4) and the proton transfer is rate limiting (KIE ≈ 11). The activation parameters were found to be ΔH ⧧ = 17.7 kcal mol–1 and ΔS ⧧ = −27.1 cal mol–1 K–1. DFT analyses have provided support for these findings and suggest that aryl phosphinite C–H nickelation proceeds via an ion-pair-assisted deprotonation.

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Synthesis of unsymmetrical 5,6-POCOP′-type pincer complexes of nickel(ii): impact of nickelacycle size on structures and spectroscopic properties

Cited by 19 publications

References 53 publications

Janus POCOP Pincer Complexes of Nickel

Janus POCOP Pincer Complexes of Nickel

Recent Advances on the Chemistry of POCOP–Nickel Pincer Compounds

C–H Nickelation of Aryl Phosphinites: Mechanistic Aspects

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