Synthesis and structures of some sterically hindered zinc complexes containing 6-membered and rings

Farwell, James D.; Hitchcock, Peter B.; Läppert, Michael F.; Luinstra, Gerrit A.; Protchenko, Andrey V.; Wei, Xuehong

doi:10.1016/j.jorganchem.2008.02.012

Cited by 39 publications

(61 citation statements)

References 19 publications

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“…of methanol. [26] Another similar monometallic zinc complex was reported by Sobota and co-workers from the reaction of 2 equiv. of an amine-phenol ligand with 1 equiv.…”

Section: Resultssupporting

confidence: 61%

“…[21,37,38] The Zn-O bond distances are similar to the mean distance [2.039 Å] from a literature survey and are comparable with related zinc complexes reported in the literature. [26,35,[38][39][40][41] The single crystal structure determination of complex 3 depicted in Figure 5 reveals a centrosymmetric bimetallic complex with the zinc centres bridged through the oxygen atoms of the phenolate ligands. The geometry at the zinc atom is distorted tetrahedral.…”

Section: X-ray Crystallographic Analyses Of Zinc Complexesmentioning

confidence: 99%

“…The Zn-C, Zn-N and Zn-O bond distances are within the ranges previously reported for zinc complexes. [1,26,39,43] The ethyl groups on each of the two metal centres lay trans to each other. Presumably, the larger tert-butyl group in the 4-position of the phenolate donor in 3, although distant from the metal coordination sphere, causes the ethyl groups to orientate themselves in a trans arrangement in contrast to the syn-(cis) arrangement in 2, where the 4-position of the phenolate group is a methyl.…”

Section: X-ray Crystallographic Analyses Of Zinc Complexesmentioning

confidence: 99%

“…[24] Of particular relevance to the current study, Carpentier and co-workers recently described the synthesis of zinc and magnesium complexes supported by ether-aminephenolate ligands, including those bearing morpholinyl side-arms, as effective initiators for immortal ROP of cyclic esters. [25] Also, Lappert and co-workers have reported zinc complexes stabilized by a piperazinylphenolate ligand, [26] one such complex was found to uptake some CO 2 when attempts at cyclohexene oxide-CO 2 copolymerizations were undertaken although no polymer was isolated.…”

Section: Introductionmentioning

confidence: 99%

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Zinc Complexes of Piperazinyl‐Derived Aminephenolate Ligands: Synthesis, Characterization and Ring–Opening Polymerization Activity

et al. 2011

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A series of zinc complexes was prepared from 4,6‐disubstituted (R,R′) o‐[(4‐methyl‐1‐piperazinyl)methyl]phenols ([ONNR′,R]H) and characterized by elemental analysis, 1H and 13C{1H} NMR spectroscopy, and X‐ray crystallography. Reaction of these products with diethylzinc gave Zn[ONNtBu,tBu]2 (1) as a monometallic complex and {[μ‐ONNR′,R]ZnEt}2 [R′ = Me, R = tBu, (2); R′ = R = tBu (3); R′ = R = tAm (4)] bimetallic species that have distorted tetrahedral environments about the Zn centres. Reaction of 3 and 4 with alcohols gave {[ONNtAm,tAm]Zn(μ‐OR″)}2 [R″ = Bn (5); R″ = Et (6)] bimetallic species in which the Zn centres are bridged by benzyl alkoxide and ethoxide groups, respectively. A morpholinyl derived ligand was also synthesized and characterized (L4H), and its 1:1 stoichiometric reaction with ZnEt2 resulted in complex 7, {[μ‐ONOtBu,tBu]ZnEt}2. The reactivity of complexes 2–7 in the ring‐opening polymerization of rac‐lactide (LA) and ϵ‐caprolactone (ϵ‐CL) was studied. Reactions of carbon dioxide with cyclohexene oxide in the presence of 6 or 7/ROH (R = Bn, Et) afforded cyclohexene carbonate.

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“…of methanol. [26] Another similar monometallic zinc complex was reported by Sobota and co-workers from the reaction of 2 equiv. of an amine-phenol ligand with 1 equiv.…”

Section: Resultssupporting

confidence: 61%

Section: X-ray Crystallographic Analyses Of Zinc Complexesmentioning

confidence: 99%

Section: X-ray Crystallographic Analyses Of Zinc Complexesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Zinc Complexes of Piperazinyl‐Derived Aminephenolate Ligands: Synthesis, Characterization and Ring–Opening Polymerization Activity

et al. 2011

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“…Some complexes of these ligands (L1-L3) have been reported by our group and others, and will allow us to compare reactivity where data are available from these prior studies. 10,27,28,31,32,39 Compounds 1-5 were synthesized through alkane elimination reactions using two equivalents of the appropriate protio ligands with the corresponding alkyl/halide aluminum precursors (AlMe 3 or Et 2 AlCl) in dry toluene as summarized in Scheme 27 Al NMR spectroscopy. The 1 H NMR spectra of 1-3 confirmed that the complexes were monometallic with two coordinated aminephenolate ligands.…”

Section: Synthesis and Solid-state Structuresmentioning

confidence: 99%

Aluminum Methyl and Chloro Complexes Bearing Monoanionic Aminephenolate Ligands: Synthesis, Characterization, and Use in Polymerizations

et al. 2012

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Abstract:A series of aluminum methyl and chloride complexes bearing 2(N-piperazinyl-N′-methyl)-2-methylene-4-R′-6-R-phenolate or 2(N-morpholinyl)-2-methylene-4-R′-6-R-phenolate ([ONE R1,R2 ]-) {[ R 1 = t Bu, R 2 = Me, E = NMe (L1); R 1 = R 2 = t Bu, E = NMe (L2); R 1 = R 2 = t Bu, 1 E = O (L3)} ligands were synthesized and characterized through elemental analysis, 1 H, 13 The catalytic activity of complexes 1-3 toward ring-opening polymerization (ROP) of ε-caprolactone was assessed. These complexes are more active than analogous Zn complexes for this reaction but less active than the Zn analogs for ROP of rac-lactide. Characteristics of the polymer as well as polymerization kinetics and mechanism were studied. Polymer end-group analyses were achieved using 1 H NMR spectroscopy and MALDI-TOF MS. Eyring analyses were performed and the activation energies for the reactions were determined, which were significantly lower for 1 and 2 compared with 3. This could be for several reasons: (1) the methylamine (NMe) group of 1 and 2, which is a stronger base than the ether (O) group of 3, might activate the incoming monomer via non-covalent interactions, and/or (2) the ether group is able to temporarily coordinate to the metal center and blocks the vacant coordination site towards incoming monomer, whilst the amine cannot do this. Preliminary studies using 4 and 5 towards copolymerization of cyclohexene oxide with carbon dioxide have been performed. 4 was inactive and 5 afforded polyethercarbonate (66.7% epoxide conversion, polymer contains 54.0% carbonate linkages).

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Zinc Complexes of β‐Ketoiminato Ligands as Efficient Catalysts for the Synthesis of α‐Amino Nitriles via Strecker Reaction

et al. 2020

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We report the synthesis of α‐aminonitriles by one‐pot coupling reaction of aldehyde, amines and trimethylsilyl cyanide (TMSCN) using β‐ketoiminato zinc complexes as a pre‐catalyst in very good yield under mild reaction condition. Homoleptic zinc complex [{κ2‐(2,4,6‐Me3C6H2NC(Me)=CHC(Me)=O)}2Zn] (1 a) was synthesized by the treatment of protic ligand [(2,4,6‐Me3C6H2NHC(Me)=CHC(Me)=O)] (L1H) with potassium hydride and anhydrous zinc diiodide in 2 : 2 : 1 molar ratio in THF. Analogous reactions using [(2,6‐iPr2C6H3NHC(Me)=CHC(Me)=O)] (L2H) and [(Ph2CHNHC(Me)=CHC(Me)=O)] (L3H) as protic ligands, dinuclear zinc complexes [{κ3‐(2,6‐iPr2C6H3NC(Me)=CHC(Me)=O)}ZnI]2 (1 b) and [Zn(Ph2CHNHC−(Me)=CHC(Me)=O)ZnI2] (1 c) were obtained in good yield. Molecular structures of ligands L1H, L3H, and zinc complexes 1 a, 1 b, and 1 c were established by single‐crystal x‐ray diffraction analysis. Dinuclear zinc complexes 1 b, and 1 c exhibited high transformation, greater selectivity and broad substrate scope for the synthesis of α‐aminonitrile under mild condition. A most plausible mechanism for synthesis α‐aminonitrile is proposed based on several controlled reactions.

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Synthesis and structures of some sterically hindered zinc complexes containing 6-membered and rings

Cited by 39 publications

References 19 publications

Zinc Complexes of Piperazinyl‐Derived Aminephenolate Ligands: Synthesis, Characterization and Ring–Opening Polymerization Activity

Zinc Complexes of Piperazinyl‐Derived Aminephenolate Ligands: Synthesis, Characterization and Ring–Opening Polymerization Activity

Aluminum Methyl and Chloro Complexes Bearing Monoanionic Aminephenolate Ligands: Synthesis, Characterization, and Use in Polymerizations

Zinc Complexes of β‐Ketoiminato Ligands as Efficient Catalysts for the Synthesis of α‐Amino Nitriles via Strecker Reaction

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