Co-complexation syntheses, structural characterization, and DFT studies of a novel series of polymeric alkali-metal tetraorganogallates

David R. Armstrong, Elanor Brammer, Thomas Cadenbach, Eva Hevia, Alan R. Kennedy

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Exploring the co-complexation reactions between the gallium alkyl Ga(CH2SiMe3)(3) and alkali-metal alkyl MCH2SiMe3 (M = Li, Na, or K) using an arene/hexane solvent mixture has allowed the isolation of solvent-free alkali-metal tetraorganogallates [{MGa(CH2SiMe3)(4)}(infinity)] (M = Li, 1; Na, 2) and related benzene adduct [{(C6H6)(2)KGa-(CH2SiMe3)(4))(infinity)] (3). By combining X-ray crystallography, NMR spectroscopy, and DFT calculations, this study sheds new light on the constitution of these mixed-metal species. Xray crystallographic studies reveal that all gallates exhibit novel polymeric arrangements, with 1 and 2 sharing the same linear chain structure, made up exclusively of M-C and Ga-C bonds, whereas 3 displays a significantly more open structural motif, where the K and Ga atoms are connected by a single alkyl bridge and propagation occurs via weaker K center dot center dot center dot Me electrostatic interactions of a methyl from a SiMe3 group of an alkyl ligand from one monomer to the potassium from a neighboring monomeric unit. Multinuclear NMR spectroscopic studies suggest that in deuterated benzene solutions 1-3 exist as discrete solvent-separated ion-pair species where the alkali-metal is solvated by the arene solvent. DFT calculations show that while the infinite aggregation of these polymeric structures is key for thermodynamically favoring the formation of 1 and 2, in the case of 3 the solvation of unsaturated potassium by two molecules of benzene, via pi-electrostatic interactions, appears to be the major contributor to its overall stability.

LanguageEnglish
Pages480-489
Number of pages10
JournalOrganometallics
Volume32
Issue number2
Early online date11 Jan 2013
DOIs
Publication statusPublished - 28 Jan 2013

Fingerprint

Alkali Metals
Complexation
Discrete Fourier transforms
alkali metals
Benzene
benzene
synthesis
Coulomb interactions
infinity
potassium
Potassium
electrostatics
gallates
nuclear magnetic resonance
Gallium
constitution
X ray crystallography
Solvation
Hexanes
Nuclear magnetic resonance spectroscopy

Keywords

  • NMR Spectroscopy
  • alkali-metal
  • benzene
  • chemical stability

Cite this

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abstract = "Exploring the co-complexation reactions between the gallium alkyl Ga(CH2SiMe3)(3) and alkali-metal alkyl MCH2SiMe3 (M = Li, Na, or K) using an arene/hexane solvent mixture has allowed the isolation of solvent-free alkali-metal tetraorganogallates [{MGa(CH2SiMe3)(4)}(infinity)] (M = Li, 1; Na, 2) and related benzene adduct [{(C6H6)(2)KGa-(CH2SiMe3)(4))(infinity)] (3). By combining X-ray crystallography, NMR spectroscopy, and DFT calculations, this study sheds new light on the constitution of these mixed-metal species. Xray crystallographic studies reveal that all gallates exhibit novel polymeric arrangements, with 1 and 2 sharing the same linear chain structure, made up exclusively of M-C and Ga-C bonds, whereas 3 displays a significantly more open structural motif, where the K and Ga atoms are connected by a single alkyl bridge and propagation occurs via weaker K center dot center dot center dot Me electrostatic interactions of a methyl from a SiMe3 group of an alkyl ligand from one monomer to the potassium from a neighboring monomeric unit. Multinuclear NMR spectroscopic studies suggest that in deuterated benzene solutions 1-3 exist as discrete solvent-separated ion-pair species where the alkali-metal is solvated by the arene solvent. DFT calculations show that while the infinite aggregation of these polymeric structures is key for thermodynamically favoring the formation of 1 and 2, in the case of 3 the solvation of unsaturated potassium by two molecules of benzene, via pi-electrostatic interactions, appears to be the major contributor to its overall stability.",
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Co-complexation syntheses, structural characterization, and DFT studies of a novel series of polymeric alkali-metal tetraorganogallates. / Armstrong, David R.; Brammer, Elanor; Cadenbach, Thomas; Hevia, Eva; Kennedy, Alan R.

In: Organometallics, Vol. 32, No. 2, 28.01.2013, p. 480-489.

Research output: Contribution to journalArticle

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T1 - Co-complexation syntheses, structural characterization, and DFT studies of a novel series of polymeric alkali-metal tetraorganogallates

AU - Armstrong, David R.

AU - Brammer, Elanor

AU - Cadenbach, Thomas

AU - Hevia, Eva

AU - Kennedy, Alan R.

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AB - Exploring the co-complexation reactions between the gallium alkyl Ga(CH2SiMe3)(3) and alkali-metal alkyl MCH2SiMe3 (M = Li, Na, or K) using an arene/hexane solvent mixture has allowed the isolation of solvent-free alkali-metal tetraorganogallates [{MGa(CH2SiMe3)(4)}(infinity)] (M = Li, 1; Na, 2) and related benzene adduct [{(C6H6)(2)KGa-(CH2SiMe3)(4))(infinity)] (3). By combining X-ray crystallography, NMR spectroscopy, and DFT calculations, this study sheds new light on the constitution of these mixed-metal species. Xray crystallographic studies reveal that all gallates exhibit novel polymeric arrangements, with 1 and 2 sharing the same linear chain structure, made up exclusively of M-C and Ga-C bonds, whereas 3 displays a significantly more open structural motif, where the K and Ga atoms are connected by a single alkyl bridge and propagation occurs via weaker K center dot center dot center dot Me electrostatic interactions of a methyl from a SiMe3 group of an alkyl ligand from one monomer to the potassium from a neighboring monomeric unit. Multinuclear NMR spectroscopic studies suggest that in deuterated benzene solutions 1-3 exist as discrete solvent-separated ion-pair species where the alkali-metal is solvated by the arene solvent. DFT calculations show that while the infinite aggregation of these polymeric structures is key for thermodynamically favoring the formation of 1 and 2, in the case of 3 the solvation of unsaturated potassium by two molecules of benzene, via pi-electrostatic interactions, appears to be the major contributor to its overall stability.

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