Alkali metal and magnesium enamides from metallation of the alkyl ligands [(2-Pyr)(SiMe3)CH2 and [6-Me-(2-Pyr)(SiMe3)CH2]: a solid state and ab initio study

Philip C. Andrews, David R. Armstrong, Colin L. Raston, Brett A. Roberts, Brian W. Skelton, Allan H. White

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Abstract

The alkali metal complexes [rNa·(pmdta)]2, 1, [rK·(pmdta)]2, 2, [rNa·(tmeda)]2, 3, [r′Li·(pmdta)], 4, and the magnesium complex, [(r)2Mg·(hmpa)2], 5, formed on metallation of the monosilylated ligands [(2-Pyr)(SiMe3)CH2] (= rH) and [6-Me-(2-Pyr)(SiMe3)CH2] (= r′H), rather than being metal alkyls, are all metal enamides in the solid state, as evidenced by single crystal X-ray diffraction studies. Even in the presence of the bi- and tri-dentate donors tmeda (= N,N,N′,N′-tetramethylethylenediamine) and pmdta (= N,N,N′,N′,N″-pentamethyldiethylenetriamine) the heavier alkali metal complexes are found to be dimeric. The Li complex is monomeric and adopts the enamide configuration despite the presence of additional steric bulk on introduction of a Me group on the 6-position of the pyridyl ring. This preference for an enamide configuration, rather than that of carbanion or aza-allyl, has been studied by ab initio MO calculations. These confirmed that as the coordination environment of the metal increases the enamide form rather then the aza-allylic form becomes the most energetically favoured configuration.
LanguageEnglish
Pages996-1006
Number of pages11
JournalJournal of the Chemical Society, Dalton Transactions
Volume1472
Issue number7
DOIs
Publication statusPublished - 2001

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Alkali Metals
Magnesium
Metals
Coordination Complexes
Ligands
RNA
Heavy metals
Single crystals
X ray diffraction

Keywords

  • alkali metal
  • magnesium
  • pyridyl ring

Cite this

Andrews, Philip C. ; Armstrong, David R. ; Raston, Colin L. ; Roberts, Brett A. ; Skelton, Brian W. ; White, Allan H. / Alkali metal and magnesium enamides from metallation of the alkyl ligands [(2-Pyr)(SiMe3)CH2 and [6-Me-(2-Pyr)(SiMe3)CH2] : a solid state and ab initio study. In: Journal of the Chemical Society, Dalton Transactions. 2001 ; Vol. 1472, No. 7. pp. 996-1006.
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abstract = "The alkali metal complexes [rNa·(pmdta)]2, 1, [rK·(pmdta)]2, 2, [rNa·(tmeda)]2, 3, [r′Li·(pmdta)], 4, and the magnesium complex, [(r)2Mg·(hmpa)2], 5, formed on metallation of the monosilylated ligands [(2-Pyr)(SiMe3)CH2] (= rH) and [6-Me-(2-Pyr)(SiMe3)CH2] (= r′H), rather than being metal alkyls, are all metal enamides in the solid state, as evidenced by single crystal X-ray diffraction studies. Even in the presence of the bi- and tri-dentate donors tmeda (= N,N,N′,N′-tetramethylethylenediamine) and pmdta (= N,N,N′,N′,N″-pentamethyldiethylenetriamine) the heavier alkali metal complexes are found to be dimeric. The Li complex is monomeric and adopts the enamide configuration despite the presence of additional steric bulk on introduction of a Me group on the 6-position of the pyridyl ring. This preference for an enamide configuration, rather than that of carbanion or aza-allyl, has been studied by ab initio MO calculations. These confirmed that as the coordination environment of the metal increases the enamide form rather then the aza-allylic form becomes the most energetically favoured configuration.",
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Alkali metal and magnesium enamides from metallation of the alkyl ligands [(2-Pyr)(SiMe3)CH2 and [6-Me-(2-Pyr)(SiMe3)CH2] : a solid state and ab initio study. / Andrews, Philip C.; Armstrong, David R.; Raston, Colin L.; Roberts, Brett A.; Skelton, Brian W.; White, Allan H.

In: Journal of the Chemical Society, Dalton Transactions, Vol. 1472, No. 7, 2001, p. 996-1006.

Research output: Contribution to journalArticle

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T1 - Alkali metal and magnesium enamides from metallation of the alkyl ligands [(2-Pyr)(SiMe3)CH2 and [6-Me-(2-Pyr)(SiMe3)CH2]

T2 - Journal of the Chemical Society, Dalton Transactions

AU - Andrews, Philip C.

AU - Armstrong, David R.

AU - Raston, Colin L.

AU - Roberts, Brett A.

AU - Skelton, Brian W.

AU - White, Allan H.

PY - 2001

Y1 - 2001

N2 - The alkali metal complexes [rNa·(pmdta)]2, 1, [rK·(pmdta)]2, 2, [rNa·(tmeda)]2, 3, [r′Li·(pmdta)], 4, and the magnesium complex, [(r)2Mg·(hmpa)2], 5, formed on metallation of the monosilylated ligands [(2-Pyr)(SiMe3)CH2] (= rH) and [6-Me-(2-Pyr)(SiMe3)CH2] (= r′H), rather than being metal alkyls, are all metal enamides in the solid state, as evidenced by single crystal X-ray diffraction studies. Even in the presence of the bi- and tri-dentate donors tmeda (= N,N,N′,N′-tetramethylethylenediamine) and pmdta (= N,N,N′,N′,N″-pentamethyldiethylenetriamine) the heavier alkali metal complexes are found to be dimeric. The Li complex is monomeric and adopts the enamide configuration despite the presence of additional steric bulk on introduction of a Me group on the 6-position of the pyridyl ring. This preference for an enamide configuration, rather than that of carbanion or aza-allyl, has been studied by ab initio MO calculations. These confirmed that as the coordination environment of the metal increases the enamide form rather then the aza-allylic form becomes the most energetically favoured configuration.

AB - The alkali metal complexes [rNa·(pmdta)]2, 1, [rK·(pmdta)]2, 2, [rNa·(tmeda)]2, 3, [r′Li·(pmdta)], 4, and the magnesium complex, [(r)2Mg·(hmpa)2], 5, formed on metallation of the monosilylated ligands [(2-Pyr)(SiMe3)CH2] (= rH) and [6-Me-(2-Pyr)(SiMe3)CH2] (= r′H), rather than being metal alkyls, are all metal enamides in the solid state, as evidenced by single crystal X-ray diffraction studies. Even in the presence of the bi- and tri-dentate donors tmeda (= N,N,N′,N′-tetramethylethylenediamine) and pmdta (= N,N,N′,N′,N″-pentamethyldiethylenetriamine) the heavier alkali metal complexes are found to be dimeric. The Li complex is monomeric and adopts the enamide configuration despite the presence of additional steric bulk on introduction of a Me group on the 6-position of the pyridyl ring. This preference for an enamide configuration, rather than that of carbanion or aza-allyl, has been studied by ab initio MO calculations. These confirmed that as the coordination environment of the metal increases the enamide form rather then the aza-allylic form becomes the most energetically favoured configuration.

KW - alkali metal

KW - magnesium

KW - pyridyl ring

U2 - 10.1039/b009596f

DO - 10.1039/b009596f

M3 - Article

VL - 1472

SP - 996

EP - 1006

JO - Journal of the Chemical Society, Dalton Transactions

JF - Journal of the Chemical Society, Dalton Transactions

SN - 0300-9246

IS - 7

ER -