Structural and vibrational properties of silyl (SiH3-) anions in KSiH3 and RbSiH3: New insight into Si-H interactions

Verina F. Kranak, Yuan Chih Lin, Maths Karlsson, J. Mink, Stefan T. Norberg, Ulrich Häussermann

Research output: Contribution to journalArticle

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Abstract

The alkali metal silyl hydrides ASiH3 (A = K, Rb) and their deuteride analogues were prepared from the Zintl phases ASi. The crystal structures of ASiH3 consist of metal cations and pyramidal SiH3- ions. At room temperature SiH3- moieties are randomly oriented (α modifications). At temperatures below 200 K ASiH3 exist as ordered low-temperature (β) modifications. Structural and vibrational properties of SiH3- in ASiH3 were characterized by a combination of neutron total scattering experiments, infrared and Raman spectroscopy, as well as density functional theory calculations. In disordered α-ASiH3 SiH3- ions relate closely to freely rotating moieties with C3v symmetry (Si-H bond length = 1.52 Å; H-Si-H angle 92.2 °). Observed stretches and bends are at 1909/1903 cm-11, A1), 1883/1872 cm-13, E), 988/986 cm-14, E), and 897/894 cm-12, A1) for A = K/Rb. In ordered β-ASiH3 silyl anions are slightly distorted with respect to their ideal C3v symmetry. Compared to α-ASiH3 the molar volume is by about 15% smaller and the Si-H stretching force constant is reduced by 4%. These peculiarities are attributed to reorientational dynamics of SiH3- anions in α-ASiH3. Si-H stretching force constants for SiH3- moieties in various environments fall in a range from 1.9 to 2.05 N cm-1. These values are considerably smaller compared to silane, SiH4 (2.77 N cm-1). The reason for the drastic reduction of bond strength in SiH3- remains to be explored.

Original languageEnglish
Pages (from-to)2300-2309
Number of pages10
JournalInorganic Chemistry
Volume54
Issue number5
DOIs
Publication statusPublished - Mar 2 2015

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Anions
anions
deuterides
Hydrogen
Stretching
metal hydrides
symmetry
silanes
Ions
alkali metals
Alkali Metals
Silanes
ions
Raman spectroscopy
infrared spectroscopy
Bond length
interactions
analogs
density functional theory
cations

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Structural and vibrational properties of silyl (SiH3-) anions in KSiH3 and RbSiH3 : New insight into Si-H interactions. / Kranak, Verina F.; Lin, Yuan Chih; Karlsson, Maths; Mink, J.; Norberg, Stefan T.; Häussermann, Ulrich.

In: Inorganic Chemistry, Vol. 54, No. 5, 02.03.2015, p. 2300-2309.

Research output: Contribution to journalArticle

Kranak, Verina F. ; Lin, Yuan Chih ; Karlsson, Maths ; Mink, J. ; Norberg, Stefan T. ; Häussermann, Ulrich. / Structural and vibrational properties of silyl (SiH3-) anions in KSiH3 and RbSiH3 : New insight into Si-H interactions. In: Inorganic Chemistry. 2015 ; Vol. 54, No. 5. pp. 2300-2309.
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abstract = "The alkali metal silyl hydrides ASiH3 (A = K, Rb) and their deuteride analogues were prepared from the Zintl phases ASi. The crystal structures of ASiH3 consist of metal cations and pyramidal SiH3- ions. At room temperature SiH3- moieties are randomly oriented (α modifications). At temperatures below 200 K ASiH3 exist as ordered low-temperature (β) modifications. Structural and vibrational properties of SiH3- in ASiH3 were characterized by a combination of neutron total scattering experiments, infrared and Raman spectroscopy, as well as density functional theory calculations. In disordered α-ASiH3 SiH3- ions relate closely to freely rotating moieties with C3v symmetry (Si-H bond length = 1.52 {\AA}; H-Si-H angle 92.2 °). Observed stretches and bends are at 1909/1903 cm-1 (ν1, A1), 1883/1872 cm-1 (ν3, E), 988/986 cm-1 (ν4, E), and 897/894 cm-1 (ν2, A1) for A = K/Rb. In ordered β-ASiH3 silyl anions are slightly distorted with respect to their ideal C3v symmetry. Compared to α-ASiH3 the molar volume is by about 15{\%} smaller and the Si-H stretching force constant is reduced by 4{\%}. These peculiarities are attributed to reorientational dynamics of SiH3- anions in α-ASiH3. Si-H stretching force constants for SiH3- moieties in various environments fall in a range from 1.9 to 2.05 N cm-1. These values are considerably smaller compared to silane, SiH4 (2.77 N cm-1). The reason for the drastic reduction of bond strength in SiH3- remains to be explored.",
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T1 - Structural and vibrational properties of silyl (SiH3-) anions in KSiH3 and RbSiH3

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AU - Lin, Yuan Chih

AU - Karlsson, Maths

AU - Mink, J.

AU - Norberg, Stefan T.

AU - Häussermann, Ulrich

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AB - The alkali metal silyl hydrides ASiH3 (A = K, Rb) and their deuteride analogues were prepared from the Zintl phases ASi. The crystal structures of ASiH3 consist of metal cations and pyramidal SiH3- ions. At room temperature SiH3- moieties are randomly oriented (α modifications). At temperatures below 200 K ASiH3 exist as ordered low-temperature (β) modifications. Structural and vibrational properties of SiH3- in ASiH3 were characterized by a combination of neutron total scattering experiments, infrared and Raman spectroscopy, as well as density functional theory calculations. In disordered α-ASiH3 SiH3- ions relate closely to freely rotating moieties with C3v symmetry (Si-H bond length = 1.52 Å; H-Si-H angle 92.2 °). Observed stretches and bends are at 1909/1903 cm-1 (ν1, A1), 1883/1872 cm-1 (ν3, E), 988/986 cm-1 (ν4, E), and 897/894 cm-1 (ν2, A1) for A = K/Rb. In ordered β-ASiH3 silyl anions are slightly distorted with respect to their ideal C3v symmetry. Compared to α-ASiH3 the molar volume is by about 15% smaller and the Si-H stretching force constant is reduced by 4%. These peculiarities are attributed to reorientational dynamics of SiH3- anions in α-ASiH3. Si-H stretching force constants for SiH3- moieties in various environments fall in a range from 1.9 to 2.05 N cm-1. These values are considerably smaller compared to silane, SiH4 (2.77 N cm-1). The reason for the drastic reduction of bond strength in SiH3- remains to be explored.

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