Synthesis, Structure and Solution Studies on Mixed Aryl/Alkyl Lithium Zincates

Roberts, Andrew J.; Kennedy, Alan R.; McLellan, Ross; Robertson, Stuart D.; Hevia, Eva

doi:10.1002/ejic.201601020

Cited by 9 publications

(5 citation statements)

References 64 publications

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“…Lithium bis(trimethylsilyl)amide (LiHMDS) was purchased from Sigma Aldrich and stored in the glovebox as received. Phenyllithium, MesN(H)C 2 H 4 NH 2 , 1‐bromo‐2‐(9‐fluorenyl)ethane and 1,3‐bis(2,6‐diisopropylphenyl)imidazolidin‐2‐ylidene (SIPr) were synthesised according to literature procedures. NMR spectra were obtained on either a Bruker AVIII 300, AVIII 400 or AVIIHD 400 MHz spectrometer.…”

Section: Methodsmentioning

confidence: 99%

Lithium Complexes with Bridging and Terminal NHC Ligands: The Decisive Influence of an Anionic Tether

et al. 2019

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Deprotonation of the fluorenyl‐tethered imidazolinium salt [9‐(C13H9)C2H4N(CH)C2H4N(2,4,6‐Me3C6H2)][BF4] gave a spirocyclic compound that reacted with a synergic mixture of LiPh/LiN(SiMe3)2 or LinBu/LiN(SiMe3)2 to give a dilithium complex incorporating a bridging N(SiMe3)2 ligand. In contrast, deprotonation of the imidazolium salt [9‐(C13H9)C2H4N(CH)C2H2N(Me)][Br] instead yielded the free NHC, which reacted with nBuLi to form a dimeric, NHC‐bridged dilithium complex. Addition of LiN(SiMe3)2 led to coordination and the formation of a dilithium complex with a bridging N(SiMe3)2 ligand, which was characterised in the solid state as a 1D coordination polymer. The reaction of 1,3‐bis(2,6‐diisopropylphenyl)‐4,5‐dihydroimidazol‐2‐ylidene (SIPr) with lithium indenide and lithium fluorenide gave soluble species with terminal binding of the NHC to the lithium cation and η5 coordination of indenyl or fluorenyl. A symmetrical bridging mode for an NHC donor was therefore observed only if a tethered fluorenyl anion was present with no additional amide ligand.

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Section: Methodsmentioning

confidence: 99%

Lithium Complexes with Bridging and Terminal NHC Ligands: The Decisive Influence of an Anionic Tether

et al. 2019

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“…Cocomplexation reactions are not always so straightforward. For example, adding one equivalent of the donor solvent TMEDA to a 1:1 hexane mixture of Zn(CH 2 SiMe 3 ) 2 and phenyllithium at ambient temperature resulted in formation of the homoleptic alkylzincate [(TMEDA)LiZn(CH 2 SiMe 3 ) 3 ] ( 176 , Figure ) instead of the expected heteroleptic complex [(TMEDA)LiZn(Ph)(CH 2 SiMe 3 ) 2 ] . The formation of the homoleptic alkylzincate is presumed to be due to a disproportionation process.…”

Section: Heterometallic Synergistic Main Group Complexesmentioning

confidence: 99%

Alkali-Metal-Mediated Synergistic Effects in Polar Main Group Organometallic Chemistry

2019

Self Cite

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The development of synthetic chemistry since the early 1900s owes much to the service of organolithium reagents. Brilliant bases (e.g., deprotonating C−H bonds), nucleophiles (e.g., adding to unsaturated molecules), and transfer agents (e.g., delivering ligands to other metals), these versatile virtuosi and to a lesser extent the organic derivatives of the other common alkali metals sodium and potassium have proved indispensable in both academia and technology. Today these monometallic compounds are still utilized widely in synthetic campaigns, but in recent years they have been joined by an assortment of bimetallic formulations that also contain an alkali metal but in company with another metal. These bimetallic formulations often exhibit unique chemistry that can be interpreted in terms of synergistic effects, for which the alkali metal is essential, though it is often the second metal that performs the synthetic transformation. Here, this "alkali-metal-mediated" chemistry is surveyed focusing mainly on bimetallic formulations containing two alkali metals or an alkali metal paired with magnesium, calcium, zinc, aluminum, or gallium. In this International Year of the Periodic Table (IYPT), we ponder whether a Pairiodic Table of Element Pairs will emerge in the future.

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“…We aimed to develop another type of initiator to overcome the drawbacks observed with the use of n BuLi·(tmeda). Me 3 SiCH 2 Li readily forms zincate species ([R 2 (Me 3 SiCH 2 )Zn] + [Li] − ) with R 2 Zn, and selective growth of the PS chains from R-Zn sites in [R 2 (Me 3 SiCH 2 )Zn] + [Li] − can be expected, leaving the Zn-CH 2 SiMe 3 sites intact, based upon the fact that Me 3 SiCH 2 Li is a poor initiator for styrene polymerization. In fact, high-molecular-weight PS ( M n , 280 kDa) with a broad molecular weight distribution ( M w / M n , 1.80) was generated with a use of a [styrene]/[Me 3 SiCH 2 Li] feed ratio of 250, indicating that only ∼10% of Me 3 SiCH 2 Li participates in the initiation process.…”

Section: Resultsmentioning

confidence: 99%

Biaxial Chain Growth of Polyolefin and Polystyrene from 1,6-Hexanediylzinc Species for Triblock Copolymers

Park

Kim

et al. 2017

Macromolecules

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Synthesis of polyolefin (PO)-based block copolymers is of immense research interest. In this work, we report a strategy for the construction of polystyrene (PS)-block-PO-block-PS, a useful thermoplastic elastomer, directly from olefin and styrene monomers. Multinuclear zinc species Et[Zn(CH2)6] a ZnEt were prepared through successive additions of BH3 and Et2Zn to 1,5-hexadiene. Poly(ethylene-co-propylene) chains were biaxially grown from the −(CH2)6– units in Et[Zn(CH2)6] a ZnEt via “coordinative chain transfer polymerization (CCTP)” using the pyridylaminohafnium catalyst. PS chains were subsequently grown in one pot from the generated polymeryl–Zn sites by subsequent introduction of the anionic initiator Me3SiCH2Li·(pmdeta) (pmdeta, pentamethyldiethylenetriamine) and styrene monomers. The fraction of the extracted PS homopolymer grown from the Me3SiCH2 sites was low (homo-PS (g)/total PS (g), 15–22%). The gel permeation chromatography (GPC) curves shifted evidently after styrene polymerization, and change in the molecular weight (ΔM n, 39–56 kDa) was approximately twice the homo-PS M n (20–23 kDa), in accordance with attachment of the PS chains at both ends of the PO chains. Transmission electron microscopy analysis of the thin films showed segregation of the PS domains in the PO matrix to form spherical or wormlike rippled structures depending on the PS content. The prepared triblock copolymers exhibited elastomeric properties in the cyclic tensile test, similar to the commercial PS-block-poly(ethylene-co-1-butene)-block-PS.

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Synthesis, Structure and Solution Studies on Mixed Aryl/Alkyl Lithium Zincates

Cited by 9 publications

References 64 publications

Lithium Complexes with Bridging and Terminal NHC Ligands: The Decisive Influence of an Anionic Tether

Lithium Complexes with Bridging and Terminal NHC Ligands: The Decisive Influence of an Anionic Tether

Alkali-Metal-Mediated Synergistic Effects in Polar Main Group Organometallic Chemistry

Biaxial Chain Growth of Polyolefin and Polystyrene from 1,6-Hexanediylzinc Species for Triblock Copolymers

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