Synthesis, characterization of the dilithium bis-azaallyl complex [CH 2 C(NAr)C(NAr) CH 2 ]Li 2 (THF) 4 and its catalytic activity for the anionic polymerization of methyl methacrylate

Treatment of N,N 0 -bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1,3-butadiene with MeLi results in carbon-carbon bond formation and selective reduction of one of the imine arms to give the N-lithiated salt of the imine/amine, N,N 0 -bis(2,6-diisopropylphenyl)-1,4-diaza-2,3,3-trimethyl-1-butene. This compound crystallizes from Et 2 O as a solvent adduct, exists as a monomer both in solution and the solid state, and features a three-coordinate lithium nucleus that is chelated to oxygen, amido, and imino donors. In contrast, treatment of N,N 0 -bis(2,4,6-trimethylphenyl)-1,4-diaza-2,3-dimethyl-1,3-butadiene with MeLi gives the N-lithiated imine anion N-(2,4,6trimethylphenyl)-1-aza-2-methyl-3-N 0 -(2,4,6-trimethylphenyl)-1,3-butadiene, as the ether adduct, by proton abstraction. With a more hindered base, N,N 0 -bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1,3-butadiene undergoes proton abstraction with lithium diisopropylamide to give the N-lithiated imine anion of the ene/amine, N-(2,6-diisopropylphenyl)-1-aza-2-methyl-3-N 0 -(2,6-diisopropylphenyl)-1,3butadiene, again isolated as the ether adduct. A further equiv of MeLi 3 LiBr added to N-(2,4,6trimethylphenyl)-1-aza-2-methyl-3-N 0 -(2,4,6-trimethylphenyl)-1,3-butadiene gives the doubly N-lithiated salt of the diene/diamide, 2,3-N,N 0 -bis(2,4,6-trimethylphenyl)-1,3-butadiene, in which both nitrogen centers have been reduced, and which adopts a cisoid stereochemistry with respect to the butadiene unit in the solid state.

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Sterically Hindered Diazabutadienes (DABs): Competing Reaction Pathways with MeLi

Bhadbhade

Clentsmith²,

Field³

2010

Organometallics

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Sodium and Magnesium Complexes with Dianionic α-Diimine Ligands

Liu

Yang

et al. 2008

Organometallics

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A series of sodium and magnesium complexes with α-diimine ligands, [Na2(L iPr)(Et2O)]2 (1, L iPr = [(2,6- i Pr2C6H3)N(Me)C]2), [Na2(LMes)(solv)2]2 (LMes = [(2,4,6-Me3C6H3)N(Me)C]2, 2a, solv = Et2O; 2b, solv = THF), [Na4(LEt)2] n (3, LEt = [(2,6-Et2C6H3)N(Me)C]2), and [Mg(LMes)(THF)3] (4), have been synthesized by reduction of the diimine ligands with sodium or magnesium metal. Single-crystal X-ray diffraction analysis revealed that the sodium complexes have a 2:1 [Na2L] unit that aggregates to dimeric (1, 2a, 2b) or polymeric (3) structures, while the magnesium complex (4) shows a monomeric 1:1 structure. In all compounds 1−4, the ligand is doubly reduced to a dianion. The two Na+ ions in 1, 2a, 2b, and 3 show different coordination modes, one of which is chelated by the N donors of a ligand with supplementary Na−C bonds to the phenyl ring of another ligand within the [Na2L]2 dimer, while the other is bonded by the central C2N2 core of the ligand and solvent molecules (1, 2a, and 2b). Compound 3 displays a novel three-dimensional network. The Mg2+ ion in 4 is coordinated by a ligand molecule and three THF molecules. Density functional theory (DFT) computations on the sodium and magnesium complexes 1 and 4 confirmed their electronic structures and the dianionic character of the ligands.

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2 Alkali and alkaline-earth metals

Gorrell

2005

Annu. Rep. Prog. Chem., Sect. A

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Highlights this year include the isolation of a new octameric form of LiOBu t , a new form of BaCp 2 , the first alkyllithium compound with a trigonal carbanion, the first primary amide of a heavy alkaline earth metal, the first positive identification of an encapsulated hydride in a Main Group cluster using neutron diffraction and an amazing compound which contains the first potassium-ferrocene bond and is the first mixed p-metallocenep-arene complex of an alkali metal.

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Synthesis, characterization of the dilithium bis-azaallyl complex [CH 2 C(NAr)C(NAr) CH 2 ]Li 2 (THF) 4 and its catalytic activity for the anionic polymerization of methyl methacrylate

Cited by 4 publications

References 10 publications

Sterically Hindered Diazabutadienes (DABs): Competing Reaction Pathways with MeLi

Sterically Hindered Diazabutadienes (DABs): Competing Reaction Pathways with MeLi

Sodium and Magnesium Complexes with Dianionic α-Diimine Ligands

2 Alkali and alkaline-earth metals

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