Mixed Lithium Amide–Lithium Halide Compounds: Unusual Halide‐Deficient Amido Metal Anionic Crowns

Kennedy, Alan R.; Mulvey, Robert E.; O’Hara, Charles T.; Robertson, Gemma M.; Robertson, Stuart D.

doi:10.1002/ange.201102023

Cited by 11 publications

(7 citation statements)

References 33 publications

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“…As H 6 -TREN commonly acts as a monomerisation agent, 4 calc -A-C were modelled as monomeric species. [42][43][44][45][46] Significantly, comparison of these model isomers revealed only a small difference in the relative energies of the three conformers, spanning just 9.00 kcal mol −1 . This closeness in the relative energy terms could be a factor in the severe disorder observed in the structure of crystalline 4.…”

Section: Structural Insights Into Sodium Dipyridylamides 2-4mentioning

confidence: 98%

Donor-activated alkali metal dipyridylamides: co-complexation reactions with zinc alkyls and reactivity studies with benzophenone

et al. 2014

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Previously it was reported that activation of (t)Bu2Zn by [(TMEDA)Na(μ-dpa)]2 led to tert-butylation of benzophenone at the challenging para-position, where the sodium amide functions as a metalloligand towards (t)Bu2Zn manifested in crystalline [{(TMEDA)Na(dpa)}2Zn(t)Bu2] (TMEDA is N,N,N',N'-tetramethylethylenediamine, dpa is 2,2'-dipyridylamide). Here we find altering the Lewis donor or alkali metal within the metalloligand dictates the reaction outcome, exhibiting a strong influence on alkylation yields and reaction selectivity. Varying the former led to the synthesis of three novel complexes, [(PMDETA)Na(dpa)]2, [(TMDAE)Na(dpa)]2, and [(H6-TREN)Na(dpa)], characterised through combined structural, spectroscopic and theoretical studies [where PMDETA is N,N,N',N'',N''-pentamethyldiethylenetriamine, TMDAE is N,N,N',N'-tetramethyldiaminoethylether and H6-TREN is N',N'-bis(2-aminoethyl)ethane-1,2-diamine]. Each new sodium amide can function as a metalloligand to generate a co-complex with (t)Bu2Zn. Reacting these new co-complexes with benzophenone proved solvent dependent with yields in THF much lower than those in hexane. Most interestingly, sub-stoichiometric amounts of the metalloligands [(TMEDA)Na(dpa)]2 and [(PMEDTA)Na(dpa)]2 with 1 : 1, (t)Bu2Zn-benzophenone mixtures produced good yields of the challenging 1,6-tert-butyl addition product in hexane (52% and 53% respectively). Although exchanging Na for Li gave similar reaction yields, the regioselectivity was significantly compromised; whereas the K system was completely unreactive. Replacing (t)Bu2Zn with (Me3SiCH2)2Zn shut down the alkylation of benzophenone; in contrast, (t)BuLi generates only the reduction product, benzhydrol. Zincation of the parent amine dpa(H) generated the crystalline product [Zn(dpa)2], as structurally elucidated through X-ray crystallography and theoretical calculations. Although the reaction mechanism for the alkylation of benzophenone remains unclear, incorporation of the radical scavenger TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl radical) into the reaction system completely inhibits benzophenone alkylation.

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Section: Structural Insights Into Sodium Dipyridylamides 2-4mentioning

confidence: 98%

Donor-activated alkali metal dipyridylamides: co-complexation reactions with zinc alkyls and reactivity studies with benzophenone

et al. 2014

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“…To the best of our knowledge, 1 constitutes the first example of a bimetallic aggregate containing all constitutents of the LICKOR base and a simple metalated hydrocarbon substrate. Thus, 1 bridges the knowledge gap between known "classical" organopotassium structures [13] and related bimetallic aggregates derived from "alkali metal mediated metalations" or bimetallic "ate" complexes. [14] The substrate sensitivity of bimetallic K/Li metalations can be exemplified by the benzylic deprotonation of toluene by Schlossers base under identical conditions.…”

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Insights into the Metalation of Benzene and Toluene by Schlosser’s Base: A Superbasic Cluster Comprising PhK, PhLi, and tBuOLi

2013

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“…a discrete Li + or Na + cation) encapsulated by a ring containing Lewis donating heteroatoms. Originally seen for heterometallic monovalent/divalent metal combinations, inverse crown chemistry has now been extended to include homometallic group 1 examples comprising solvent-separated ion pairs with host ring a neutral entity which traps a halide anion [105]. While not taking a direct role in the metallation, the choice of alkali-metal is still of paramount importance as demonstrated on changing the bimetallic base from NaMgBu(TMP)2 to KMgBu(TMP)2.…”

Section: Heteroleptic Alkyl/amido Alkali-metal Magnesiatesmentioning

confidence: 99%

Modern Developments in Magnesium Reagent Chemistry for Synthesis

Mulvey

Robertson

2013

Alkaline-Earth Metal Compounds

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This year (2012) commemorates the 100 th anniversary of the award of the Nobel Prize to Victor Grignard for his development of Grignard reagents (at the simplest level expressed as "RMgX" where R is an organic group and X is a halogen), one of the most widely utilized classes of synthetic reagent. A century on but only in the past decade or so has magnesium reagent chemistry entered a new and exciting phase, surpassing the limitations of what traditional Grignard reagents can do. Modern magnesium reagents have been designed to possess essentially comparable reactivity to their great rivals, organolithium reagents (traditional Grignard reagents are orders of magnitude less reactive than organolithium reagents) but at the same time to maintain the superior selectivity and broader functional group tolerance of their traditional ancestors. The key to the design of these new reagents is their multi-component constitution with the organomagnesium engine powered by an activating alkali metal additive, often a halide salt or another organometallic entity. This chapter outlines some of the most significant advances in this emerging field.

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Mixed Lithium Amide–Lithium Halide Compounds: Unusual Halide‐Deficient Amido Metal Anionic Crowns

Cited by 11 publications

References 33 publications

Donor-activated alkali metal dipyridylamides: co-complexation reactions with zinc alkyls and reactivity studies with benzophenone

Donor-activated alkali metal dipyridylamides: co-complexation reactions with zinc alkyls and reactivity studies with benzophenone

Insights into the Metalation of Benzene and Toluene by Schlosser’s Base: A Superbasic Cluster Comprising PhK, PhLi, and tBuOLi

Modern Developments in Magnesium Reagent Chemistry for Synthesis

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