Bis(catecholato)silicates: Synthesis and Structural Data

Abstract

This minireview provides an overview of the synthesized bis(catecholato)silicates based on the nature of the alkyl or aryl residues and associated cations as well as the methods developed for this purpose. Structural and analytical data such as the 29Si NMR shift of silicon penta‐ and hexacoordinate derivatives, selected examples of crystal structures by X‐ray diffraction analysis and oxidation potentials of silicates are reported. Some aspects of reactivity are also mentioned.

Cyclopropyl‐Substituted Trialkoxysilanes and their Related Bis(catecholato)silicates: Preparation, Characterization and Reactivity

“…The E 1/2 (ox) was determined via differential pulse voltammetry as E 1/2 ( 77 → 7 .+ ) + 0.82 and E 1/2 ( 8 → 8 .+ ) + 0.76 V versus SCE. These values were in the expected range of alkyl bis(catecholato)silicates to oxidized [12].…”

“…The preparation of hypercoordinated silicon (λ 5 Si) species [1] is nowadays mainly motivated by their multiple applications in organic chemistry. Indeed, synthesis of alkyl and aryl bis(catecholato)silicates ([R-Si(cat) 2 ] -; cat = pyrocatechol) can be performed in large scale and used in various transformations including allylation and Giese-type reactions and nickel-mediated dual catalysis [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

“…While a broad spectrum of λ 5 Si-silicate structures based on various alkyl, vinyl, or aryl groups has been synthesized [12][13][14][15][16], it is interesting to note that the cyclopropyl moiety has escaped exemplifications, probably due to the lack of commercially available starting materials. The radical/polar crossover strategy on the contrary was successfully reported by Molander for cyclopropanation reactions [10,11].…”

Cyclopropyl‐Substituted Trialkoxysilanes and their Related Bis(catecholato)silicates: Preparation, Characterization and Reactivity

“…The E 1/2 (ox) was determined via differential pulse voltammetry as E 1/2 ( 77 → 7 .+ ) + 0.82 and E 1/2 ( 8 → 8 .+ ) + 0.76 V versus SCE. These values were in the expected range of alkyl bis(catecholato)silicates to oxidized [12].…”

“…The preparation of hypercoordinated silicon (λ 5 Si) species [1] is nowadays mainly motivated by their multiple applications in organic chemistry. Indeed, synthesis of alkyl and aryl bis(catecholato)silicates ([R-Si(cat) 2 ] -; cat = pyrocatechol) can be performed in large scale and used in various transformations including allylation and Giese-type reactions and nickel-mediated dual catalysis [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

“…While a broad spectrum of λ 5 Si-silicate structures based on various alkyl, vinyl, or aryl groups has been synthesized [12][13][14][15][16], it is interesting to note that the cyclopropyl moiety has escaped exemplifications, probably due to the lack of commercially available starting materials. The radical/polar crossover strategy on the contrary was successfully reported by Molander for cyclopropanation reactions [10,11].…”

Aryl Silicon Nucleophiles in Bismuth Catalysis

“…However, this seemingly trivial synthetic approach requires that Ar-Si transmetalate to Bi, a process that is unusual for this type of tetrels, mainly due to the lower polarity of the C-Si bond when compared to C-B. [11] In this article, we report how [Ar-Si(cat) 2 À ] salts [12] can serve as viable nucleophiles in a bismuth-catalyzed synthesis of aromatic trifluoromethyl thiosulfones (Figure 1B), a motif that has no catalytic precedents for its synthesis, [13][14] and is used in various trifluoromethylthiolations, [13,15] difunctionalizations, [13,[16][17] and is present in several biologically active compounds. [18] In this work, we provide evidence for a successful aryl transmetalation event between Si and Bi, which proceeds under mild conditions in a very fast manner.…”

Development of the Dioxasilepanyl Group Si(pan): A Seven-Membered Dialkoxysilane Unit

“…This concept of stabilization by cyclization has also been applied to silicon chemistry, as demonstrated by Tomooka and Igawa's employment of benzyl-alcohol-type dialkoxysilyl group V, 16 and the bis-catecholate silicate VI, which serves as a valuable radical precursor through its cyclic dialkoxysilyl structure. 17 Furthermore, Uchiyama and Hirano demonstrated the utility of a seven-membered cyclic hydrosilane, structurally related to Si(pan), as an electrophilic silicon source. 18 Crystallographic analysis of 3,5-dichlorophenyl-Si(pan)Me (3) (CCDC 1966652) revealed that the sevenmembered ring of Si(pan) adopts a chair-like conformation.…”

Cyclopropyl‐Substituted Trialkoxysilanes and their Related Bis(catecholato)silicates: Preparation, Characterization and Reactivity

“…The E 1/2 (ox) was determined via differential pulse voltammetry as E 1/2 ( 77 → 7 .+ ) + 0.82 and E 1/2 ( 8 → 8 .+ ) + 0.76 V versus SCE. These values were in the expected range of alkyl bis(catecholato)silicates to oxidized [12].…”

“…The preparation of hypercoordinated silicon (λ 5 Si) species [1] is nowadays mainly motivated by their multiple applications in organic chemistry. Indeed, synthesis of alkyl and aryl bis(catecholato)silicates ([R-Si(cat) 2 ] -; cat = pyrocatechol) can be performed in large scale and used in various transformations including allylation and Giese-type reactions and nickel-mediated dual catalysis [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

“…While a broad spectrum of λ 5 Si-silicate structures based on various alkyl, vinyl, or aryl groups has been synthesized [12][13][14][15][16], it is interesting to note that the cyclopropyl moiety has escaped exemplifications, probably due to the lack of commercially available starting materials. The radical/polar crossover strategy on the contrary was successfully reported by Molander for cyclopropanation reactions [10,11].…”

Aryl Silicon Nucleophiles in Bismuth Catalysis

“…However, this seemingly trivial synthetic approach requires that Ar-Si transmetalate to Bi, a process that is unusual for this type of tetrels, mainly due to the lower polarity of the C-Si bond when compared to C-B. [11] In this article, we report how [Ar-Si(cat) 2 À ] salts [12] can serve as viable nucleophiles in a bismuth-catalyzed synthesis of aromatic trifluoromethyl thiosulfones (Figure 1B), a motif that has no catalytic precedents for its synthesis, [13][14] and is used in various trifluoromethylthiolations, [13,15] difunctionalizations, [13,[16][17] and is present in several biologically active compounds. [18] In this work, we provide evidence for a successful aryl transmetalation event between Si and Bi, which proceeds under mild conditions in a very fast manner.…”

Development of the Dioxasilepanyl Group Si(pan): A Seven-Membered Dialkoxysilane Unit

“…This concept of stabilization by cyclization has also been applied to silicon chemistry, as demonstrated by Tomooka and Igawa's employment of benzyl-alcohol-type dialkoxysilyl group V, 16 and the bis-catecholate silicate VI, which serves as a valuable radical precursor through its cyclic dialkoxysilyl structure. 17 Furthermore, Uchiyama and Hirano demonstrated the utility of a seven-membered cyclic hydrosilane, structurally related to Si(pan), as an electrophilic silicon source. 18 Crystallographic analysis of 3,5-dichlorophenyl-Si(pan)Me (3) (CCDC 1966652) revealed that the sevenmembered ring of Si(pan) adopts a chair-like conformation.…”

Cyclopropyl‐Substituted Trialkoxysilanes and their Related Bis(catecholato)silicates: Preparation, Characterization and Reactivity

“…The E 1/2 (ox) was determined via differential pulse voltammetry as E 1/2 ( 77 → 7 .+ ) + 0.82 and E 1/2 ( 8 → 8 .+ ) + 0.76 V versus SCE. These values were in the expected range of alkyl bis(catecholato)silicates to oxidized [12].…”

“…The preparation of hypercoordinated silicon (λ 5 Si) species [1] is nowadays mainly motivated by their multiple applications in organic chemistry. Indeed, synthesis of alkyl and aryl bis(catecholato)silicates ([R-Si(cat) 2 ] -; cat = pyrocatechol) can be performed in large scale and used in various transformations including allylation and Giese-type reactions and nickel-mediated dual catalysis [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

“…While a broad spectrum of λ 5 Si-silicate structures based on various alkyl, vinyl, or aryl groups has been synthesized [12][13][14][15][16], it is interesting to note that the cyclopropyl moiety has escaped exemplifications, probably due to the lack of commercially available starting materials. The radical/polar crossover strategy on the contrary was successfully reported by Molander for cyclopropanation reactions [10,11].…”

Aryl Silicon Nucleophiles in Bismuth Catalysis

“…However, this seemingly trivial synthetic approach requires that Ar-Si transmetalate to Bi, a process that is unusual for this type of tetrels, mainly due to the lower polarity of the C-Si bond when compared to C-B. [11] In this article, we report how [Ar-Si(cat) 2 À ] salts [12] can serve as viable nucleophiles in a bismuth-catalyzed synthesis of aromatic trifluoromethyl thiosulfones (Figure 1B), a motif that has no catalytic precedents for its synthesis, [13][14] and is used in various trifluoromethylthiolations, [13,15] difunctionalizations, [13,[16][17] and is present in several biologically active compounds. [18] In this work, we provide evidence for a successful aryl transmetalation event between Si and Bi, which proceeds under mild conditions in a very fast manner.…”

Development of the Dioxasilepanyl Group Si(pan): A Seven-Membered Dialkoxysilane Unit

“…This concept of stabilization by cyclization has also been applied to silicon chemistry, as demonstrated by Tomooka and Igawa's employment of benzyl-alcohol-type dialkoxysilyl group V, 16 and the bis-catecholate silicate VI, which serves as a valuable radical precursor through its cyclic dialkoxysilyl structure. 17 Furthermore, Uchiyama and Hirano demonstrated the utility of a seven-membered cyclic hydrosilane, structurally related to Si(pan), as an electrophilic silicon source. 18 Crystallographic analysis of 3,5-dichlorophenyl-Si(pan)Me (3) (CCDC 1966652) revealed that the sevenmembered ring of Si(pan) adopts a chair-like conformation.…”