Reactivity and Ground State Effects of Silicon in Organic Chemistry

Abstract

The strong o donor ability% the e-9' &XI manifests itself in many unusual properties of silicon-containing organic compounds. This review discusses the effect that silicon substituents have on the ground-state properties of organic compounds and on their reactivities, from this viewpoint.

Understanding Reactivity Patterns of Radical Cations

“…[60] Interestingly, the ionization potentials (IP) of allyltrimethylsilane (IP = 9.0 eV) and tetramethylsilane (IP = 9.5 eV) are even lower than that of propene (IP = 10 eV), which allows classification of both silanes as a d0nors.1~~1 Indeed, considerations of ionization potential suggest that the donor capability of a C-Si a bond is similar to that of a lone pair on oxygen. [55] Even stronger adonors are germanes and stannanes, as indicated from the ionization potentials of GeMe, (IP= 9.2 eV) and SnMe, (IP = 8.76 eV) .f491 4. Reactivity Patterns in @*+, @*+, and 0''…”

Low-temperature structure of allyl silatrane

“…As part of our general interest in the structural consequences of hyperconjugation in silicon compounds (White, 1995), we chose to determine the structure of allyl silatrane, (I). Allyl silatrane has been shown to undergo reaction with electrophiles more readily than (CH30)3Si,,/",,x~ The structure of (I) was determined at 130 K to eliminate the unwanted effects of thermal motion.…”

Modes of Neighbouring Group Participation by the Methyl Selenyl Substituent in β-Methylselenylmethyl-substituted 1-Phenylethyl Carbenium Ions

“…However, consideration was given to the possibility, that participation by the selenium substituent might occur by σ C-Se -p hyperconjugation (vertical participation), and involve the open carbenium ion 4 (Figure 1) as an intermediate [3,4,5,6]. This mode of participation is analogous to that provided by the trimethylsilyl substituent in the carbenium ion 5 (Figure 1) which is the basis of the silicon β-effect [7,8,9,10]. Application of the variable oxygen probe to ether and ester derivatives of the antiperiplanar β-phenylselenyl alcohol 6 (Figure 1) provided crystallographic evidence that the C-Se bond is a strong σ-donor and can therefore effectively stabilise a neighbouring carbenium ion by hyperconjugation alone [1].…”