Electronic Spectra of Cyclotrisilane (Si3) and Disilene (Si=Si) Frameworks

Watanabe, Hamao; Kougo, Yuichi; Kato, Motohiko; Kuwabara, Haruyoshi; Okawa, Tadashi; Nagai, Yoichiro

doi:10.1246/bcsj.57.3019

Cited by 26 publications

(7 citation statements)

References 9 publications

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“…Similarly, with the aid of the longest absorption bands of 1a (λ max 280 nm) and the corresponding linear compound Me(Me 2 Si) 5 Me (λ max 250 nm), the ring strain energy of 1a could be equally evaluated to be 12 kcal/mol. Thus, this value for 1a determined experimentally is larger than those (6 and 5.8−8.3 kcal/mol) calculated for the model compounds [H 2 Si] 5 23 and [CH 2 ] 5 , respectively, and also that (6 kcal/mol) experimentally determined previously for [R 2 Si] 5 2e because the two rings have two phenyl groups as the substituents in the molecules, the ring strain energies for 1b , c could be estimated to be ca.…”

Section: Resultscontrasting

confidence: 63%

“…UV Spectra and Ring Strain Energies of 1a − c. The three compounds 1a − c have the same longest wavelength absorption maxima at λ 280 nm (sh), with varying extinction coefficients (ε 1100, 5700, and 7600 for 1a − c , respectively), as has been shown in Figure . The absorption maximum at λ 280 nm is slightly longer than those (λ 260 ([Pr 2 Si] 5 ),2c 266 ([Et 2 Si] 5 ), and 272 nm ([Me 2 Si] 5 )) reported for the peralkylcyclopentasilanes and is different from those (251 ([Ph 2 Si] 5 ) and 294 nm ([( p -MeC 6 H 4 ) 2 Si] 5 )) for the perarylcyclopentasilanes. Interestingly, this absorption maximum (λ 280 nm) of 1a − c is almost the same as those (λ 280 ([Me 2 Si] 4 SiMePh 21 ) and 284 nm ([Me 2 Si] 4 SiPh 2 )) reported for the partially arylated cyclopentasilanes.…”

Section: Resultsmentioning

confidence: 60%

“…Interestingly, this absorption maximum (λ 280 nm) of 1a − c is almost the same as those (λ 280 ([Me 2 Si] 4 SiMePh 21 ) and 284 nm ([Me 2 Si] 4 SiPh 2 )) reported for the partially arylated cyclopentasilanes. Previously, we found that the ring strain energies of peralkylcyclosilanes can be estimated as the differences in the transition energies between the two series (linear and cyclic) of polysilanes of the same silicon numbers (ΔΔ E = Δ E (linear) − Δ E (cyclic)), using their longest absorption bands of [R 2 Si] n and Me(Me 2 Si) n Me, where n = 3−6, respectively 2e. Similarly, with the aid of the longest absorption bands of 1a (λ max 280 nm) and the corresponding linear compound Me(Me 2 Si) 5 Me (λ max 250 nm), the ring strain energy of 1a could be equally evaluated to be 12 kcal/mol.…”

Section: Resultsmentioning

confidence: 99%

“…Although a large number of studies of homosilacycles, Si n , have appeared, there are only limited reports focused on the ring systems containing germanium, Si n Ge . We have previously studied some properties of various peralkylated cyclosilanes, [R 1 R 2 Si] n ( n = 3−7) and [R 2 Si] 3 O . Recently, we reported the synthesis, molecular structure, and photolysis of four-membered [R 2 Si] 3 Ge(CH 2 SiMe 3 ) 2 ( A , R = i-Pr; B , R = t-BuCH 2 ),1b three-membered [R 2 Si] 2 Ge(CH 2 SiMe 3 ) 2 , and the four-membered oxo compound [R 2 SiGe(CH 2 SiMe 3 ) 2 SiR 2 ]O (R = t-BuCH 2 ) .…”

Section: Introductionmentioning

confidence: 99%

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Synthesis, Structure, and Photolysis of Germatetrasilacyclopentanes

et al. 1998

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The five-membered-ring systems germatetrasilacyclopentanes [R2Si]4GeR‘2 (1) (1a, R = i-Pr, R‘ = Me3SiCH2; 1b, R = i-Pr, R‘ = Ph; 1c, R = t-BuCH2, R‘ = Ph) were synthesized and characterized. The structures of 1b,c have been determined by X-ray crystallography. The Si4Ge rings of 1b,c form an envelope and a distorted half-chair conformation, respectively. The photolysis of 1 using two kinds of light sources (low- and high-pressure mercury lamps) was carried out. The photochemical decomposition of 1a afforded two types of four-membered-ring products, cyclotetrasilane (Si4; main) and germatrisilacyclobutane (Si3Ge; minor), with extrusion of germylene (Ge:) and silylene (Si:), respectively. Compounds 1b,c gave, besides the four-membered-ring products as in 1a, two types of three-membered products, cyclotrisilanes (Si3) and disilagermiranes (Si2Ge), with extrusion of silagermene (SiGe) and disilene (SiSi), respectively. This is the first case in which the unusual decomposition of five-membered rings into three-membered rings and dimetallenes has been found.

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Section: Resultscontrasting

confidence: 63%

Section: Resultsmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis, Structure, and Photolysis of Germatetrasilacyclopentanes

et al. 1998

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“…Finally, it should be emphasised that the disilaoxirane system is also a chromophore per se, and that the photolysis of hexaneopentyltrisilaoxetane ( Si30) (1) leading to tetraneopentyldisilaoxirane (Si20) (2) provides a new aspect in the chemistry of three-and four-membered peralkylcyclopolysilane systems containing a heteroatom of type Si,X (n = 2,3; X = 0, N, etc.). * * All the final products in the present photolyses were isolated by preparative g.1.c.…”

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confidence: 99%

The photolysis of a cyclopolysilane system containing a heteroatom, hexaneopentyltrisilaoxetane; evidence for the formation of a tetraneopentyldisilaoxirane

Watanabe¹,

Tabei²,

Goto³

et al. 1987

J. Chem. Soc., Chem. Commun.

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Peralkylated Four- and Five-Membered Cyclosilanes Containing a Heteroatom: Synthesis, Structure, and Properties

Watanabe

Suzuki

Takahashi

et al. 2002

Eur. J. Inorg. Chem.

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Seventeen peralkylated four-and five-membered heteroatom-containing silacycles [R 1 R 2 Si] n X [R 1 = iPr and/or R 2 = tBuCH 2 ; n = 3; X = CH 2 (1a, 1b), NR 3 (R 3 = C 6 H 11 ) (3a−d), O (5a−c), and n = 4; X = CH 2 (2a, 2b), NR 3 (R 3 = C 6 H 11 or Pr) (4a−d), and O (6a, 6b)] have been synthesized and characterized. The structural features of twelve compounds − 1b, 3a−d, and 5b (Si 3 X) and 2a, 4a−c, 6a, and 6b (Si 4 X) − determined by X-ray analysis have been investigated and geometrical differences between the silacycles bearing neopentyl groups and those with isopropyl groups as bulky substituents on silicon atoms have been identified. The ring strain energies for the compounds [R 2 Si] n X [n = 3, 4; R = Me, iPr; X = CH 2 , N(iPr), NMe, O, SiH 2 ], estimated by theoretical calculations at the PM3 level, are discussed in relation to experimentally ascertained structural features of the silacycles [R 2 Si] n X (n = 3, 4; R = iPr; X = CH 2 , NC 6 H 11 , O, SiR 2 ). 29 Si NMR spectra for 1−6 showed that the resonances for the α-silicon atoms attached to the heteroatoms X in the two ring-size series were shifted downfield by a deshielding effect due to an electronegative atom X; larger electronegativity (En) of X caused this effect at lower field. The chemical shifts of the Si α atoms showed a good linear correlation with the electronegativities of the heteroatoms X in the [R 2 Si] n X cycles. In the UV spectra for 1−6, little difference in [a] the longest-wavelength absorption (LWA) maxima was observed for [(iPr) 2 Si] n X and [(tBuCH 2 ) 2 Si] n X of the same ring size. The LWA bands for 1−6 and related compounds could be roughly classified into four groups: (a) [R 2 Si] 3 X (X = SiR 2 , GeRЈ 2 ) λ = 286−300 nm; (b) [R 2 Si] 3 X (X = CH 2 , NR 3 , O) (1, 3, 5), λ = 230−250 nm; (c) [R 2 Si] 4 X (X = SiR 2 , GeRЈ 2 ) λ = 274−280 nm; (d) [R 2 Si] 4 X (X = CH 2 , NR 3 , O) (2, 4, 6), λ = 250−260 nm. With the aid of the ionization potentials and the transition energies (E T ), the HOMO and LUMO levels for the series of compounds and the related ones were experimentally evaluated. The HOMO and LUMO levels thus obtained for [R 2 Si] 3 X and [R 2 Si] 4 X (R = iPr and tBuCH 2 ; X = SiR 2 , GeRЈ 2 , CH 2 , NC 6 H 11 , O) are discussed in terms of the calculated values and frontier orbitals on the basis of PM3 levels. The theoretical prediction for bond scission in the silacycles [(iPr) 2 Si] n X (n = 3, 4; X = CH 2 , NMe, O) in which the HOMOs and LUMOs have Si−Si bonding and antibonding character, respectively, was corroborated by the good agreement with experimental results from photolysis of the silacycles [R 2 Si] n X (n = 3, 4; R = iPr and tBuCH 2 ; X = CH 2 , NC 6 H 11 , O), with bond scission occurring only at the Si−Si bonds, and not at the Si−X bonds.

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Electronic Spectra of Cyclotrisilane (Si3) and Disilene (Si=Si) Frameworks

Cited by 26 publications

References 9 publications

Synthesis, Structure, and Photolysis of Germatetrasilacyclopentanes

Synthesis, Structure, and Photolysis of Germatetrasilacyclopentanes

The photolysis of a cyclopolysilane system containing a heteroatom, hexaneopentyltrisilaoxetane; evidence for the formation of a tetraneopentyldisilaoxirane

Peralkylated Four- and Five-Membered Cyclosilanes Containing a Heteroatom: Synthesis, Structure, and Properties

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