Reactions of chelating alkali metal amides with the Grignard reagent nBuMgCl: crystal structures and solution 1H NMR spectroscopic studies of the expected mono(amido)-product [PhCH2(Me2NCH2CH2)NMgnBu]2 and the unexpected bis(amido)-product {[Ph(2-Pyr)N]2M9 · (THF)2}

K W HENDERSON, Robert Mulvey, W CLEGG, P A ONEIL

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Abstract

Chelating alkali metal amides derived from metallation of the secondary amines PhCH2(Me2NCH2CH2)NH and Ph(2-Pyr)NH, react with the Grignard reagent (n)BuMgCl in 1:1 molar ratios to afford mono(amido) [PhCH2(Me2NCH2CH2)NMgnBu]2 1 and bis(amido) {[Ph(2-Pyr)N]2Mg.(THF)2} 2 (where THF = tetrahydrofuran) respectively. X-Ray crystallography shows 1 to be dimeric having an (amido N-Mg)2 ring, the central one of a fused tricyclic core, with the other two arising from internal complexation by the tertiary amine nitrogen atoms. Butyl ligands complete the pseudo-tetrahedral coordination of the magnesium atoms. Variable temperature H-1 NMR spectroscopic studies indicate that this structure retains its compact, highly rigid nature in arene solution, rendering it resistant to external complexation by THF. In contrast, the crystal structure of 2 is monomeric, with a pseudo-octahedral magnesium centre coordinated by two bidentate Ph(2-Pyr)N- anions and two THF molecules. Bis(amido) 2 appears to result from the THF-induced disproportionation of alkyl(amido) [Ph(2-Pyr)NMgnBu]2, a dimer akin to 1, but decidedly more flexible sterically and therefore susceptible to attack by external donor molecules.

LanguageEnglish
Pages237-250
Number of pages14
JournalJournal of Organometallic Chemistry
Volume439
Issue number3
DOIs
Publication statusPublished - 10 Nov 1992

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Alkali Metals
Alkali metals
Chelation
Complexation
Amides
alkali metals
Magnesium
amides
Amines
reagents
Crystal structure
Nuclear magnetic resonance
Atoms
nuclear magnetic resonance
crystal structure
Molecules
X ray crystallography
products
Dimers
Anions

Keywords

  • magnesium
  • lithium
  • complexes
  • alkali metal amides

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title = "Reactions of chelating alkali metal amides with the Grignard reagent nBuMgCl: crystal structures and solution 1H NMR spectroscopic studies of the expected mono(amido)-product [PhCH2(Me2NCH2CH2)NMgnBu]2 and the unexpected bis(amido)-product {[Ph(2-Pyr)N]2M9 · (THF)2}",
abstract = "Chelating alkali metal amides derived from metallation of the secondary amines PhCH2(Me2NCH2CH2)NH and Ph(2-Pyr)NH, react with the Grignard reagent (n)BuMgCl in 1:1 molar ratios to afford mono(amido) [PhCH2(Me2NCH2CH2)NMgnBu]2 1 and bis(amido) {[Ph(2-Pyr)N]2Mg.(THF)2} 2 (where THF = tetrahydrofuran) respectively. X-Ray crystallography shows 1 to be dimeric having an (amido N-Mg)2 ring, the central one of a fused tricyclic core, with the other two arising from internal complexation by the tertiary amine nitrogen atoms. Butyl ligands complete the pseudo-tetrahedral coordination of the magnesium atoms. Variable temperature H-1 NMR spectroscopic studies indicate that this structure retains its compact, highly rigid nature in arene solution, rendering it resistant to external complexation by THF. In contrast, the crystal structure of 2 is monomeric, with a pseudo-octahedral magnesium centre coordinated by two bidentate Ph(2-Pyr)N- anions and two THF molecules. Bis(amido) 2 appears to result from the THF-induced disproportionation of alkyl(amido) [Ph(2-Pyr)NMgnBu]2, a dimer akin to 1, but decidedly more flexible sterically and therefore susceptible to attack by external donor molecules.",
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TY - JOUR

T1 - Reactions of chelating alkali metal amides with the Grignard reagent nBuMgCl: crystal structures and solution 1H NMR spectroscopic studies of the expected mono(amido)-product [PhCH2(Me2NCH2CH2)NMgnBu]2 and the unexpected bis(amido)-product {[Ph(2-Pyr)N]2M9 · (THF)2}

AU - HENDERSON, K W

AU - Mulvey, Robert

AU - CLEGG, W

AU - ONEIL, P A

PY - 1992/11/10

Y1 - 1992/11/10

N2 - Chelating alkali metal amides derived from metallation of the secondary amines PhCH2(Me2NCH2CH2)NH and Ph(2-Pyr)NH, react with the Grignard reagent (n)BuMgCl in 1:1 molar ratios to afford mono(amido) [PhCH2(Me2NCH2CH2)NMgnBu]2 1 and bis(amido) {[Ph(2-Pyr)N]2Mg.(THF)2} 2 (where THF = tetrahydrofuran) respectively. X-Ray crystallography shows 1 to be dimeric having an (amido N-Mg)2 ring, the central one of a fused tricyclic core, with the other two arising from internal complexation by the tertiary amine nitrogen atoms. Butyl ligands complete the pseudo-tetrahedral coordination of the magnesium atoms. Variable temperature H-1 NMR spectroscopic studies indicate that this structure retains its compact, highly rigid nature in arene solution, rendering it resistant to external complexation by THF. In contrast, the crystal structure of 2 is monomeric, with a pseudo-octahedral magnesium centre coordinated by two bidentate Ph(2-Pyr)N- anions and two THF molecules. Bis(amido) 2 appears to result from the THF-induced disproportionation of alkyl(amido) [Ph(2-Pyr)NMgnBu]2, a dimer akin to 1, but decidedly more flexible sterically and therefore susceptible to attack by external donor molecules.

AB - Chelating alkali metal amides derived from metallation of the secondary amines PhCH2(Me2NCH2CH2)NH and Ph(2-Pyr)NH, react with the Grignard reagent (n)BuMgCl in 1:1 molar ratios to afford mono(amido) [PhCH2(Me2NCH2CH2)NMgnBu]2 1 and bis(amido) {[Ph(2-Pyr)N]2Mg.(THF)2} 2 (where THF = tetrahydrofuran) respectively. X-Ray crystallography shows 1 to be dimeric having an (amido N-Mg)2 ring, the central one of a fused tricyclic core, with the other two arising from internal complexation by the tertiary amine nitrogen atoms. Butyl ligands complete the pseudo-tetrahedral coordination of the magnesium atoms. Variable temperature H-1 NMR spectroscopic studies indicate that this structure retains its compact, highly rigid nature in arene solution, rendering it resistant to external complexation by THF. In contrast, the crystal structure of 2 is monomeric, with a pseudo-octahedral magnesium centre coordinated by two bidentate Ph(2-Pyr)N- anions and two THF molecules. Bis(amido) 2 appears to result from the THF-induced disproportionation of alkyl(amido) [Ph(2-Pyr)NMgnBu]2, a dimer akin to 1, but decidedly more flexible sterically and therefore susceptible to attack by external donor molecules.

KW - magnesium

KW - lithium

KW - complexes

KW - alkali metal amides

U2 - 10.1016/0022-328X(92)85090-J

DO - 10.1016/0022-328X(92)85090-J

M3 - Article

VL - 439

SP - 237

EP - 250

JO - Journal of Organometallic Chemistry

T2 - Journal of Organometallic Chemistry

JF - Journal of Organometallic Chemistry

SN - 0022-328X

IS - 3

ER -