Two Cyclotetrasiloxanes at 143K

Hensen, Karl; Gebhardt, F.; Kettner, M.; Pickel, Peter; Bolte, Michael

doi:10.1107/s0108270197010068

Cited by 11 publications

(7 citation statements)

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“…Once the reaction had reached completion, the product was separated from solvent. The triclinic crystalline structure as determined by XRD ( a = 10.7188 Å; b = 10.7707 Å; c = 19.1412 Å; α = 83.760°; β = 83.067°; γ = 76.140°) matched structures of Ph 8 D 4 available in literature 34,35 . IR spectra was also matched to a reference sample of Ph 8 D 4 .…”

Section: Resultsmentioning

confidence: 87%

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Selectivity of dehydrogenative silicone–oxygen bond formation in diphenylsilane by base and base‐activated catalysts

Even

Berkland

2022

Int J of Chemical Kinetics

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Various base catalysts and base‐activated catalysts were evaluated for their steric inhibitions and selectivity in silicon–oxygen bond formation between hydroxyl groups and each of the two active hydrogen sites of diphenylsilane. Three hydroxides, six amines, and an organic‐soluble N‐heterocyclic carbene‐copper alkoxide complex (CuIPr‐NHC) were reviewed using in situ FTIR monitoring of reaction progress for the stepwise consumption of both Si–H bonds in diphenylsilane in the presence of water and various alcohols. Hydroxide catalysts with sodium, potassium, and tetramethylammonium (TMA) cations showed strong dependence of cation identity on reaction rate and observable rate order but did not lead to accumulation of a once‐oxidized silane. Amine catalysts exhibited varying levels of selectivity to the once oxidized silane, leading to accumulation of diphenylsilanol and hydride terminated oligomers with relative reaction rates seemingly dependent on the size of amine's alkyl substituents. CuIPr‐NHC showed very limited reactivity to the second dehydrogenation step in comparison to the first, leading to high accumulation of once‐oxidized silane. Leveraging this, the production of diphenyl(monoalkoxy)silanes has been demonstrated with representative primary, secondary, and tertiary alcohols.

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Section: Resultsmentioning

confidence: 87%

“…Knowing little steric inhibition occurs with 1 • and 2 • alcohols with congested base anions, dehydrogenation 34,35 IR spectra was also matched to a reference sample of Ph 8 D 4 .…”

Section: Catalytic Activity By Cation Identitymentioning

confidence: 99%

Selectivity of dehydrogenative silicone–oxygen bond formation in diphenylsilane by base and base‐activated catalysts

Even

Berkland

2022

Int J of Chemical Kinetics

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“…The X-ray structures of symmetrically substituted cyclo -tetrasiloxanes exhibit (nearly) planar conformations: cyclo -(Me 2 SiO) 4 ( a = 1.000), monoclinic cyclo -(Ph 2 SiO) 4 ( a = 0.998), triclinic cyclo -(Ph 2 SiO) 4 (two molecules: a = 0.995, 0.996), and cyclo -(Cl 2 SiO) 4 ( a = 0.998). , In contrast, the molecular structures of asymmetrically substituted cyclo -tetrasiloxanes show more puckered conformations: cis cyclo- {Me 2 Si[OSi(Me)Ph] 2 SiMe 2 } ( a = 0.939), trans cyclo- {Me 2 Si[OSi(Me)Ph] 2 SiMe 2 } ( a = 0.943), and cyclo- O(Me 2 SiOSiPh 2 ) 2 O ( a = 0.959), which may be attributed to steric or crystal packing effects given the high flexibility of the parent compound. The only notable exception is cyclo- [ t -Bu 2 Si(OSiMe 2 O) 2 Si t -Bu 2 ] ( a = 1), in which the bulky tert -butyl groups induce a perfectly planar conformation.…”

Section: Resultsmentioning

confidence: 99%

“…Molecular metallasiloxanes have attracted considerable attention in recent years due to their role as model compounds for structurally modified silica surfaces or minerals, their interesting physical properties, and their potential as precursors for new inorganic materials. − A rich structural diversity of eight-membered rings incorporating various heteroatoms, such as B, Al, Ge, Sn, P, Ti, Zr, Hf, Mo, and W, exists among the cyclo -metallasiloxanes. − Single-crystal X-ray diffraction studies show that even very similar compounds can have drastically different ring conformations. A large variety of ring conformations have also been observed in the crystal structures of cyclo -tetrasiloxanes. − …”

Section: Introductionmentioning

confidence: 99%

Comparison of the Flexibility of Eight-Membered Tetrasiloxane and Stannasiloxane Rings: A Crystallographic and Computational Study

Beckmann¹,

Jurkschat²,

Schürmann³

et al. 2001

Organometallics

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The syntheses and crystal structures of the eight-membered cyclo-stannasiloxanes cyclo-[t-Bu(OH)Si(OSnt-Bu2O)2Si(OH)t-Bu] (1) and cyclo-{t-Bu2Si[OSn(CH2SiMe3)2O]2Sit-Bu2} (2) as well as the synthesis of the six-membered cyclo-stannasiloxane cyclo-{t-Bu2Si[OSn(CH2SiMe3)2]2O} (3) are reported. Compound 1 crystallizes as its trans isomer, but the cis isomer dominates in solution. In agreement with the experimentally obtained results, ab initio and DFT calculations on the model compounds cyclo-(H2SiO)4 (4), cyclo-[H2Si(OSnH2)OSiH2] (5), cyclo-O(H2SiOSnH2)2O (6), and cyclo-[H2Si(OSiH2)OSnH2] (7) indicate that the energetic preference to adopt puckered structures increases and the ring flexibility decreases with an increasing number of tin atoms in the ring. The rich diversity of puckered conformations is attributed to the steric demand of the different organic substituents.

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“…For general background to stable compounds of pentavalent, anionic silicon bearing five organic substituents, see: Couzijn et al (2004,2006,2009); Deerenberg et al (2002); de Keijzer et al (1997). For related structures, see: Malinovskii et al (2007); Steinfink et al (1955); Hensen et al (1997). For puckering analysis,, see: Evans & Boeyens (1989).…”

Section: Related Literaturementioning

confidence: 99%

2,2,6,6-Tetrakis(biphenyl-2-yl)-4,4,8,8-tetramethylcyclotetrasiloxane

et al. 2009

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The title compound, [–Si(C12H9)2OSi(CH3)2O–]2, was obtained unintentionally as the product of an attempted crystallization of caesium bis(biphenyl-2,2′-diyl)fluorosilicate from dimethylformamide. In the crystal, the molecule is located on an inversion center and the siloxane ring adopts a twist-chair conformation with the two dimethyl-substituted Si atoms lying 0.7081 (5) Å out of the plane defined by the two bis(biphenyl-2-yl)-substituted Si atoms and the four O atoms. In each Si(C12H9)2 unit, the orientation of one terminal phenyl ring relative to the phenylene ring of the other biphenyl moiety suggests a parallel displaced π–π stacking interaction [centroid distance = 4.2377 (11) Å and dihedral angle = 15.40 (9)°].

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Two Cyclotetrasiloxanes at 143K

Cited by 11 publications

References 0 publications

Selectivity of dehydrogenative silicone–oxygen bond formation in diphenylsilane by base and base‐activated catalysts

Selectivity of dehydrogenative silicone–oxygen bond formation in diphenylsilane by base and base‐activated catalysts

Comparison of the Flexibility of Eight-Membered Tetrasiloxane and Stannasiloxane Rings: A Crystallographic and Computational Study

2,2,6,6-Tetrakis(biphenyl-2-yl)-4,4,8,8-tetramethylcyclotetrasiloxane

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