Structure and reactivity of lithium amides.  Lithium-6, carbon-13, and nitrogen-15 NMR spectroscopic studies and colligative measurements of lithium diphenylamide and lithium diphenylamide-lithium bromide complex solvated by tetrahydrofuran

DePue, Jeffrey S.; Collum, David B.

doi:10.1021/ja00224a041

Cited by 64 publications

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“…At high concentrations of THF only the monomeric version of 2h is observed, although the degree of THF solvation could not be established. 38 Collectively, these investigations show that while in the solid state some subtle variations in the degree of aggregation and solvation of the lithium amides using either 2-MeTHF or THF as a donor are observed, nearly identical constitutions are detected in solution when using both of these ethereal solvents, favoring trisolvated LiAS 3 monomers. Considering the close interplay of aggregation and solvent effects with reactivity patterns in lithium amide chemistry, 39 a plausible rationale for the fast amidation (and transamidation) reactions observed in our study could be the formation of kinetically activated aggregates of the lithium amides in 2-MeTHF solution.…”

Section: Resultsmentioning

confidence: 89%

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Ultrafast amidation of esters using lithium amides under aerobic ambient temperature conditions in sustainable solvents

et al. 2020

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Section: Resultsmentioning

confidence: 89%

“…At high concentrations of THF only the monomeric version of 2h is observed, although the degree of THF solvation could not be established. 38 …”

Section: Resultsmentioning

confidence: 99%

Ultrafast amidation of esters using lithium amides under aerobic ambient temperature conditions in sustainable solvents

et al. 2020

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“…Because the 1 H and 13 C NMR spectroscopic data obtained for 1 and 2 suggest that tmeda remains coordinated to the respective alkali metal atom, and only one set of diphenylamido resonances are observed in C 6 D 6 , it appears that only one oligomer of solvated alkali metal amide [presumably the dimeric solid-state species (vide infra)] exists in solution, [32] although there is precedent for other dimeric sblock metal species to slowly convert to other oligomers Scheme 1. Syntheses of 1, 2, and 3.…”

Section: Preparation and Solution Structuresmentioning

confidence: 99%

“…The solution structure of LiNPh 2 in thf (in the presence/absence of LiBr) has been comprehensively studied by Collum. [32,33] In the solid state, the majority of the complexes reported to date, take the form of solventseparated alkali metal ate species, whereby the second metal is a transition metal, [34][35][36][37][38] lanthanide, [39][40][41][42][43][44][45] actinide, [46] or a group 13 element. [47,48] Contacted ate complexes are also prevalent, predominantly with the heavier alkali metals (sodium and potassium) due to their need for further stabilisation by metal-arene π-interactions.…”

Section: Introductionmentioning

confidence: 99%

Structural Elucidation of tmeda‐Solvated Alkali Metal Diphenylamide Complexes

et al. 2009

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Lithium, sodium and potassium salts of diphenylamine have been prepared by using a deprotonative route and characterised in both, solid state (by X‐ray crystallography) and solution (by NMR spectroscopic studies). In each case the metal atom's coordination sphere is completed by coordination to the synthetically important co‐ligand N,N,N′,N′‐tetramethylethylenediamine (tmeda). Complexes 1 and 2 [{(tmeda)M(NPh2)}2] (M = Li for 1, Na for 2) can be prepared by treating 1 mol.‐equiv. of the parent amine with an equimolar quantity of nBuM and tmeda in hexane solution. In the solid state, 1 and 2 are essentially isostructural, being dimeric with a four‐atom M–N–M–N framework. The coordination sphere of each M atom is completed by a bidentate tmeda molecule. Complex 3 [{(tmeda)3/2K(NPh2)}2] has been prepared in a similar way to 1 and 2 except that benzylpotassium has been utilised as the metallating agent. In addition, 4 mol‐equiv. of tmeda is required to fully solubilise the heavy alkali metal amide mixture. In the solid state, 3 exists as a polymeric array of dinuclear K–N–K–N rings. Akin to 1 and 2, the K atom is coordinated to a bidentate tmeda molecule; however, each K atom is also bound to another tmeda molecule that acts as a monodentate bridge, thus producing the coordination polymer. Crystalline 1 and 2 are soluble in C6D6; hence, NMR spectroscopic studies could be performed. These show that the solid‐state structure appears to stay intact in arene solution. On the other hand, 3 is not soluble in C6D6; so solution studies have been performed in [D8]thf. These studies reveal that 3 readily looses tmeda during in‐vacuo isolation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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“…Lithium amide compounds, LiNR 2 (R = alkyl, aryl or silyl), have proven to be ubiquitous in organometallic chemistry as amide transfer reagents and also as mild deprotonation reagents for organic synthesis − These studies have revealed a remarkable diversity of bonding types in solution and the solid state, with solvent-separated ion pairs, monomers, dimers, trimers, tetramers, larger oligomers, polymers, ladders, and cages all being known. 1,16-18 What becomes evident from these reports is that the coordination geometry of organolithium reagents is not straightforward and can often vary between the solution and the solid states.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization, and Solution Dynamics of Alkali-Metal Chloride, Aluminate, and Borate Adducts of the Tridentate Amido Diphosphine Ligand Precursor LiN(SiMe₂CH₂PPrⁱ₂)₂

1997

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The preparation of LiCl, LiAlMe 4 , LiAlEt 4 , LiBEt 4 , and NaBEt 4 adducts of the lithium salt of the potentially tridentate ligand precursor LiN(SiMe 2 CH 2 PPr i 2 ) 2 is reported. The reaction of HN(SiMe 2 CH 2 Cl) 2 with LiPPr i 2 (3 equiv) in THF at -78°C leads to the isolation of {LiN(SiMe 2 CH 2 PPr i 2 ) 2 } 2 LiCl, under certain conditions. The X-ray crystal structure shows it to exist as a 2:1 adduct with pseudo C 2 symmetry in which a LiCl molecule is sandwiched between two LiN(SiMe 2 CH 2 PPr i 2 ) 2 monomers. The LiCl molecule and two Li-N units form a planar six-membered core which can best be described as a three-rung ladder. The solution 1 H NMR spectrum is consistent with this geometry. Variable-temperature 31 P and 7 Li NMR spectroscopy indicate that the basic structural features of this compound are maintained in solution. This is confirmed by a 7 Li NOESY experiment. The addition of LiAlMe 4 to LiN(SiMe 2 CH 2 PPr i 2 ) 2 results in the formation of {LiN(SiMe 2 CH 2 PPr i 2 ) 2 ‚LiAlMe 4 } 2 ; the same product is formed upon the addition of MeLi (4 equiv) to AlCl 2 [N(SiMe 2 CH 2 PPr i 2 ) 2 ]. The X-ray crystal structure of this product indicates that a 2:2 dimer of C 2 symmetry is present. Variable-temperature NMR studies are consistent with a highly fluxional molecule under ambient conditions. The variable-temperature 6 Li NMR spectra of the multiply labeled derivative { 6 Li 15 N(SiMe 2 CH 2 PPr i 2 ) 2 ‚ 6 LiAlMe 4 } 2 indicate that lithium exchange is occurring faster than phosphine exchange. Interaggregate lithium exchange is present under ambient conditions, while at lower temperatures, intraaggregate exchange is more favorable. The behavior of this species varies greatly upon dissolution in coordinating solvents. LiAlEt 4 and LiBEt 4 adducts of LiN(SiMe 2 CH 2 PPr i 2 ) 2 were also formed but could not be crystallized and thus studied in the solid state. The addition of NaBEt 4 to LiN(SiMe 2 CH 2 PPr i 2 ) 2 affords {LiN(SiMe 2 CH 2 PPr i 2 ) 2 ‚NaBEt 4 } x . The X-ray crystal structure of this compound shows it to be an infinite one-dimensional polymer. In this case, the elucidated structure is the result of aggregation upon solvent evaporation. Comparison of the three crystal structures illustrates that even with varying adducts (i.e., LiCl, LiAlMe 4 , and NaBEt 4 ) the basic geometries of the LiN(SiMe 2 CH 2 PPr i 2 ) 2 unit remain similar.

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Structure and reactivity of lithium amides. Lithium-6, carbon-13, and nitrogen-15 NMR spectroscopic studies and colligative measurements of lithium diphenylamide and lithium diphenylamide-lithium bromide complex solvated by tetrahydrofuran

Cited by 64 publications

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Ultrafast amidation of esters using lithium amides under aerobic ambient temperature conditions in sustainable solvents

Ultrafast amidation of esters using lithium amides under aerobic ambient temperature conditions in sustainable solvents

Structural Elucidation of tmeda‐Solvated Alkali Metal Diphenylamide Complexes

Synthesis, Characterization, and Solution Dynamics of Alkali-Metal Chloride, Aluminate, and Borate Adducts of the Tridentate Amido Diphosphine Ligand Precursor LiN(SiMe₂CH₂PPrⁱ₂)₂

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Structure and reactivity of lithium amides. Lithium-6, carbon-13, and nitrogen-15 NMR spectroscopic studies and colligative measurements of lithium diphenylamide and lithium diphenylamide-lithium bromide complex solvated by tetrahydrofuran

Cited by 64 publications

References 0 publications

Ultrafast amidation of esters using lithium amides under aerobic ambient temperature conditions in sustainable solvents

Ultrafast amidation of esters using lithium amides under aerobic ambient temperature conditions in sustainable solvents

Structural Elucidation of tmeda‐Solvated Alkali Metal Diphenylamide Complexes

Synthesis, Characterization, and Solution Dynamics of Alkali-Metal Chloride, Aluminate, and Borate Adducts of the Tridentate Amido Diphosphine Ligand Precursor LiN(SiMe2CH2PPri2)2

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Synthesis, Characterization, and Solution Dynamics of Alkali-Metal Chloride, Aluminate, and Borate Adducts of the Tridentate Amido Diphosphine Ligand Precursor LiN(SiMe₂CH₂PPrⁱ₂)₂