173977-40-7Relevant academic research and scientific papers
Thermal Stabilization of the Silaethene Ph2Si=C(SiMe3)2
Wiberg, Nils,Link, Matthias
, p. 1241 - 1250 (2007/10/03)
Silaethene Ph2Si=C(SiMe3)2 (3) (generated from Ph2SiBr-CLi(SiMe3)2 = 3*LiBr in Et2O at -78 deg C) reversibly isomerizes fast by methyl migration, then a bit slower by phenyl migration, and finally fast by methyl migration into thermodynamically more stable Me2Si=C(SiMePh2)(SiMe3) (3a), then into medium stable PhMeSi=C(SiMe2Ph)(SiMe3) (3b), and finally into most stable Me2Si=C(SiMe2Ph)2 (3c) (cf.Schemes 1 and 2; Figure 1).Simultaneously with isomerization 3a -> 3c cycloadditions (dimerizations) of 3a and 3c occur (formation of 3a * 3a, 3a * 3c, 3c * 3c; cf.Scheme 2).Over and above that, silaethenes 3a and 3c irreversibly isomerize into disilaindanes 4a, 4b, and 4c (cf.Scheme 6).Certainly, the latter reactions are even slow at 100 deg C.Thermolysis of 3a * 3a, 3a * 3c, 3c * 3c at 340 deg C, on the other hand, leads by way of cycloreversion and the intermediate formation of an equilibrium mixture of 3, 3a, 3b, 3c almost quantitatively to 4.In addition to the thermolysis products mentioned above, products of 3 and its isomers 3a, 3b, 3c with the solvents (for example Et2O; cf.Scheme 7), with the silaethene sources (for example 3 * LiBr; cf.Scheme 8), or with products formed from sources besides silaethene 3 (for example Ph2C=N-SiMe3; cf.Scheme 4) are observed. - Keywords: Methyl and phenyl group migrations in Ph2Si=C(SiMe3)2 ; Silaethenes Me2Si=C(SiMePh2)(SiMe3), PhMeSi=(SiMe2Ph)(SiMe3), Me2Si=C(SiMe2Ph)2 ; Silaethene dimers ; Disilaindanes ; Silaethene reactions with Et2O and with Ph2SiBr-CLi(SiMe3)2 ; Insertions of silaethenes into SiN bond of Ph2C=N-SiMe3
Reactivity of the Silaethene Ph2Si=C(SiMe3)2
Wilberg, Nils,Link, Matthias
, p. 1231 - 1240 (2007/10/03)
Silaethene Ph2Si=C(SiMe3)2 (3), generated as a reaction intermediate by the thermal elimination of LiX from Ph2SiX-CLi(SiMe3)2 (X = Br, F) or by the thermal cycloreversion of the cycloadduct of 3 and Ph2C=NSiMe3, forms adducts 3*donor, the stability of which increases in the order of donor = Et2O according to an ene reaction, with a=b (e.g.CH2=CHOMe; Ph2C=NSiMe3) or a=b=c (e.g. (t-Bu)2RSiN3, R = Me, t-Bu) or a=b-c=d with or or cycloaddition.The following order of relative reactivity of trapping reagents for Ph2Si=C(SiMe3)2 was found: Ph2CO > (t-Bu)2MeSiN3 > butadiene > 2,3-dimethylbutadiene > Ph2CNSiMe3 > (t-Bu)3SiN3 > anthracene.Summing up, it may be said that going from Me2Si=C(SiMe3)2 to Ph2Si=C(SiMe3)2 there is only a gradual but not principal change of silaethene reactivity.This change is due to increasing polarity and overcrowding of the double bond, that is increasing Lewis acidity and steric hindrance of the unsaturated silicon atom.Certainly, the former silaethene stabilizes thermally by dimerization, the latter by isomerization. - Keywords: Adduct formations, insertions, ene reactions, -, -, -cycloadditions of Ph2Si=C(SiMe3)2 ; Reactivity order of traps ; Reactivity of Me2Si=C(SiMe3)2 and Ph2Si=C(SiMe3)2
