Stabilization of positive charge by .beta.-silicon

Vertical and Nonvertical Participation by Sulfur, Selenium, and Tellurium

“…[9] The reduction for both unbiased systems comes from an admixture of the slower diequatorial form, in which the dihedral angle is approximately 608. The fact that the enhancement is still very large comes from two factors.…”

“…Thus, if CAr-S1-C2 101.31 (9) 100.69 (9) 104.71 (8) 102.34 (8) 107.37 (12) 106.31 (9) 105.88(8) O1-C1-C6…”

Structural evidence for σC-Sn - σ*C-O hyperconjugation: Low temperature crystalstructure of r-5-methyl-c-2-trimethylstannylcyclohexan-1-t-ol

“…[1][2][3][4] The most well known of these effects is the silicon β effect 2 which is best exemplified by the relative rates of unimolecular solvolysis of the antiperiplanar β-trimethylsilyl ester 1 which reacts 10 12 times faster than the corresponding silicon free derivative 2. 3 The remarkable rate enhancement of 1 suggests stabilisation of the intermediate β-silyl carbenium ion 3 of ca. 18 kcal/mol.…”

“…to 2) is consistent with the and the carbenium p orbital. 3 It has been demonstrated that stannyl and germyl substituents have an even greater stabilising effect on positive charge at the β position. 5 For example the trimethylgermyl ester 5 and the trimethylstannyl ester 6 react at rates 10 14 and >>10 14 times faster than the corresponding metal free analogs.…”

Elektronenreiche Olefine, 2 Struktur und Elektrontransfer-Reaktivität des cyclisch σ/π-hyperkonjugierten Carbosilans 3,3,6,6-Tetrakis(trimethylsilyl)-1,4-cyclohexadien

“…Oxidierbarkeit [7] und demnach eine Stabilisierung carbo- [8,9] und Radikal-kationischer Spezies [5] durch ß-Silyl-Substitution zur Folge hat.…”