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Compounds exhibiting main group elements in low oxidation states were found to mimic the reactivity of transition metal complexes. Like the latter, such main group species show a proclivity of changing their oxidation state as well as their coordination number by +2, therefore fulfilling the requirements for oxidative additions. Prominent examples of such main group compounds that undergo oxidative additions with organohalides R−X (R=alkyl, aryl, X=F, Cl, Br, I) are carbenes and their higher congeners. Aluminyl anions, which like carbenes and silylenes oxidatively add to strong σ‐bonds in R−X species, have been recently discovered. We present the first anion based upon a Group 14 element, namely the tris(pentafluoroethyl)silanide anion, [Si(C2F5)3]−, which is capable of oxidative additions towards C−F bonds. This enables the isolation of non‐chelated tetraorganofluorosilicate salts, which to the best of our knowledge had only been observed as reactive intermediates before. [ABSTRACT FROM AUTHOR]

While alkyl‐substituted siloxanes are widely known, virtually nothing is known about perfluoroalkyl siloxanes and their congener species, the silanols and silanolates. We recently reported on the tris(pentafluoroethyl)silanide ion, [Si(C2F5)3]−, which features Lewis amphoteric character deriving from the pentafluoroethyl substituents and their strong electron‐withdrawing properties. Transferring this knowledge, we investigated the Lewis amphoteric behavior of the tris(pentafluoroethyl)silanolate, [Si(C2F5)3O]−. In order to examine such Lewis amphoteric behavior, we first developed a strategy for the synthesis of the corresponding silanol Si(C2F5)3OH, which readily condenses at room temperature to the hexakis(pentafluoroethyl)disiloxane, (C2F5)3SiOSi(C2F5)3. Deprotonation of Si(C2F5)3OH employing a sterically demanding phosphazene base allows the characterization of the first example of a dimeric triorganosilanolate: the dianionic hexakis(pentafluoroethyl)disilanolate, [{Si(C2F5)3O}2]2−, implies Lewis amphoteric character of the monomeric [Si(C2F5)3O]− anion. [ABSTRACT FROM AUTHOR]

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In this contribution we present an account on pentafluoroethylated compounds of silicon, germanium and tin. The pronounced electron‐withdrawing effect of the pentafluoroethyl group leads to a markedly increased Lewis acidity at the central atom which results in the stabilization of hypervalent complexes, anionic element(II) species as well as remarkable reactivities of element‐element and element‐hydrogen bonds. By addition to unsaturated C−C bonds or by reaction with organic halides as well as transition‐metal complexes the molecules bearing a pentafluoroethyl‐element group are readily accessible. Moreover, the utilization of pentafluoroethyl groups facilitates the formation of donor‐stabilized germylenes and stannylenes. A series of such compounds serves as suitable pentafluoroethylation reagents. Conversely to the well‐studied trifluoromethyl derivatives these compounds frequently exhibit a higher thermostability, which allows a more convenient handling. The introduction of electron‐withdrawing pentafluoroethyl groups into organosilicon, organogermanium and organotin compounds creates a pronounced electron‐deficiency at the central atom, which leads to a significantly different chemical behavior with respect to non‐fluorinated derivatives. These characteristics facilitate the formation of hypervalent complexes, stabilization of low‐valent species as well as main group and transition‐metal complexes. [ABSTRACT FROM AUTHOR]

The tris(pentafluoroethyl)silanide anion is accessible by the deprotonation of Si(C2F5)3H at low temperatures. Subsequent quenching of the resulting salt-like compounds with suitable electrophiles, such as transition-metal complexes or Group 14 element halides, leads to a plethora of novel tris(pentafluoroethyl)silane derivatives. This underlines the versatility of Li[Si(C2F5)3] as a powerful nucleophilic transfer reagent. [ABSTRACT FROM AUTHOR]

As recently shown, the introduction of pentafluoroethyl functionalities into silicon compounds is of general interest due to an enhanced Lewis acidity of the resulting species. By this means, the synthesis of previously inaccessible hypervalent silicon derivatives is enabled. While an easy access to tris(pentafluoroethyl)silanes has already been published, synthetic strategies for the selective preparation of bis derivatives are yet unknown. In this contribution, a convenient protocol for the synthesis of functional bis(pentafluoroethyl)silicon compounds is presented. These compounds represent precursors for the synthesis of pentafluoroethylated polysiloxanes. Furthermore, they prove to be resistant to oxonium cations, which is a key feature for the preparation of stable pentafluoroethylsilic acids. Treatment of dichlorodiphenoxysilane with in situ generated pentafluoroethyl lithium leads to the corresponding bis(pentafluoroethyl)silane in high yields. (C2F5)2Si(OPh)2 serves as a starting material for further functionalized bis(pentafluoroethyl)silanes. These silanes have been isolated and their reactivity towards N bases studied. The pronounced Lewis acidity of the obtained compounds has been documented by the formation of octahedral adducts with nitrogen donors such as 1,10-phenanthroline and acetonitrile. [ABSTRACT FROM AUTHOR]

The addition of BCl3 to the carbene-transfer reagent NHC→SiCl4 (NHC=1,3-dimethylimidazolidin-2-ylidene) gave the tetra- and pentacoordinate trichlorosilicon(IV) cations [(NHC)SiCl3]+ and [(NHC)2SiCl3]+ with tetrachloroborate as counterion. This is in contrast to previous reactions, in which NHC→SiCl4 served as a transfer reagent for the NHC ligand. The addition of BF3 ⋅OEt2, on the other hand, gave NHC→BF3 as the product of NHC transfer. In addition, the highly Lewis acidic bis(pentafluoroethyl)silane (C2F5)2SiCl2 was treated with NHC→SiCl4. In acetonitrile, the cationic silicon(IV) complexes [(NHC)SiCl3]+ and [(NHC)2SiCl3]+ were detected with [(C2F5)SiCl3]− as counterion. A similar result was already reported for the reaction of NHC→SiCl4 with (C2F5)2SiH2, which gave [(NHC)2SiCl2H][(C2F5)SiCl3]. If the reaction medium was changed to dichloromethane, the products of carbene transfer, NHC→Si(C2F5)2Cl2 and NHC→Si(C2F5)2ClH, respectively, were obtained instead. The formation of the latter species is a result of chloride/hydride metathesis. These compounds may serve as valuable precursors for electron-poor silylenes. Furthermore, the reactivity of NHC→SiCl4 towards phosphines is discussed. The carbene complex NHC→PCl3 shows similar reactivity to NHC→SiCl4, and may even serve as a carbene-transfer reagent as well. [ABSTRACT FROM AUTHOR]

Pure anhydrous hexafluorosilicic acid (H2[SiF6]) is a still elusive species, although its existence in aqueous solutions is well documented. Desiccation inevitably leads to decomposition to form tetrafluorosilane and hydrogen fluoride. An oxonium hexafluorosilicate turned out to not be stable at room temperature. Partial substitution of the fluorine atoms with strong electron-withdrawing perfluoroalkyl groups results in substantial stabilization of the corresponding fluorosilicic acids. Mono- and bis(pentafluoroethyl)-substituted fluorosilicic acids were prepared through conversion of the respective halosilanes (Si(C2F5) nX4− n, with X=Cl, Br) with aqueous HF, and were obtained as colorless solids. They can be stored at room temperature for several months without decomposition, and thus are the first examples of stable fluorosilicic acids. [ABSTRACT FROM AUTHOR]

Fluorine, Oxidative Addition, Perfluorosilicates, Silanide Anion, Silicon Frontispiece: Oxidative Additions of C-F Bonds to the Silanide Anion [Si(C2F5)3]- Keywords: Fluorine; Oxidative Addition; Perfluorosilicates; Silanide Anion; Silicon EN Fluorine Oxidative Addition Perfluorosilicates Silanide Anion Silicon 1 1 1 04/14/22 20220419 NES 220419 B Silicon b In their Research Article (e202116468), Berthold Hoge et al. report oxidative additions of [Si(C SB 2 sb F SB 5 sb ) SB 3 sb ] SP - sp to aryl- and alkenylfluorides, enabling the isolation of tetraorganofluorosilicate salts devoid of chelating ligands. [Extracted from the article]

Silicon In their Research Article (e202116468), Berthold Hoge et al. report oxidative additions of [Si(C2F5)3]− to aryl‐ and alkenylfluorides, enabling the isolation of tetraorganofluorosilicate salts devoid of chelating ligands. [ABSTRACT FROM AUTHOR]

Keywords: Fluor; Oxidative Addition; Perfluorosilicate; Silanid-Anion; Silicium DE Fluor Oxidative Addition Perfluorosilicate Silanid-Anion Silicium 1 1 1 04/12/22 20220419 NES 220419 B Silicium b In ihrem Forschungsartikel (e202116468) berichten Berthold Hoge et al. über oxidative Additionen von [Si(C SB 2 sb F SB 5 sb ) SB 3 sb ] SP - sp an Aryl- und Alkenylfluoride, welche die Isolierung von Tetraorganofluorosilicatsalzen frei von chelatisierende Liganden ermöglichen. Frontispiz: Oxidative Addition von C-F-Bindungen an das Silanid-Anion [Si(C2F5)3]-. [Extracted from the article]

Keywords: Lewis amphoteric; perfluoroalkyls; silicon; silanolates; silanol; siloxanes EN Lewis amphoteric perfluoroalkyls silicon silanolates silanol siloxanes 11018 11018 1 08/04/21 20210802 NES 210802 B The tris(pentafluoroethyl)silanol b , Si(C SB 2 sb F SB 5 sb ) SB 3 sb OH, flashes out of the shadows of silanol derivatives in the cover image, paving the way to its disiloxane and disilanolate. Lewis amphoteric, perfluoroalkyls, silicon, silanolates, silanol, siloxanes Cover Feature: Tris(pentafluoroethyl)silanol Derivatives and the Lewis Amphoteric Tris(pentafluoroethyl)silanolate Anion, [Si(C2F5)3O]- (Chem. Eur. J. 43/2021). [Extracted from the article]

The research area of perfluoroalkylsilanes is still in its infancy. Although there are already many examples of difluorotriorganylsilicates, the first example of a completely characterized trifluorotriorganylsilicate is presented, the dianion [Si(C2F5)3F3]2−. The strongly electron-withdrawing influence of the pentafluoroethyl groups appears to be a fundamental cause of the stability of this compound. This dianion is also the first structurally characterized example of a tris(pentafluoroethyl)silicon compound. The synthesis and complete characterization of [PPh4]2[Si(C2F5)3F3] and [PPh4][Si(C2F5)3F2] along with the precursor [H(OEt2)2][Si(C2F5)3F2] was achieved from SiCl4 and LiC2F5. [ABSTRACT FROM AUTHOR]

Frontispiz: Synthese und Reaktivität der ersten isolierten wasserstoffverbrückten Silanol-Silanolat-Anionen Keywords: Phosphazen; Schwach koordinierende Kationen; Silanolat; Silicon; Siloxan DE Phosphazen Schwach koordinierende Kationen Silanolat Silicon Siloxan 1 1 1 03/23/20 20200327 NES 200327 B Siliciumverbindungen b Isolierte Silanolat-Anionen wurden von B. Hoge et al. in ihrer Zuschrift auf S. 5536 durch Reaktion von Phosphazenium-Hydroxid-Hydrat-Salzen mit Siloxanen synthetisiert. Der schwach koordinierende Charakter des Kations führt zu einer starken Nukleophilie des Anions und damit zu Silanol-Silanolat-H-Brücken. [Extracted from the article]

The introduction of electron‐withdrawing pentafluoroethyl groups into organosilicon, organogermanium and organotin compounds by the treatment of organo‐element halides with LiC2F5 creates a pronounced electron‐deficiency at the central atom with respect to non‐fluorinated derivatives. For silicon, germanium and tin reliable protocols for a cleavage of the organic protecting groups allow the synthesis of the Lewis acidic pentafluoroethyl‐element halides E(C2F5)4−nXn (E=Si, Ge, Sn; n=1–3). For a detailed discussion of this field of research see the Concept article by M. Wiesemann and B. Hoge on page 16457 ff. [ABSTRACT FROM AUTHOR]

The cover page of the journal "Angewandte Chemie" is presented.

Compounds exhibiting main group elements in low oxidation states were found to mimic the reactivity of transition metal complexes. Like the latter, such main group species show a proclivity of changing their oxidation state as well as their coordination number by +2, therefore fulfilling the requirements for oxidative additions. Prominent examples of such main group compounds that undergo oxidative additions with organohalides R−X (R=alkyl, aryl, X=F, Cl, Br, I) are carbenes and their higher congeners. Aluminyl anions, which like carbenes and silylenes oxidatively add to strong σ‐bonds in R−X species, have been recently discovered. We present the first anion based upon a Group 14 element, namely the tris(pentafluoroethyl)silanide anion, [Si(C2F5)3]−, which is capable of oxidative additions towards C−F bonds. This enables the isolation of non‐chelated tetraorganofluorosilicate salts, which to the best of our knowledge had only been observed as reactive intermediates before. [ABSTRACT FROM AUTHOR]

While alkyl‐substituted siloxanes are widely known, virtually nothing is known about perfluoroalkyl siloxanes and their congener species, the silanols and silanolates. We recently reported on the tris(pentafluoroethyl)silanide ion, [Si(C2F5)3]−, which features Lewis amphoteric character deriving from the pentafluoroethyl substituents and their strong electron‐withdrawing properties. Transferring this knowledge, we investigated the Lewis amphoteric behavior of the tris(pentafluoroethyl)silanolate, [Si(C2F5)3O]−. In order to examine such Lewis amphoteric behavior, we first developed a strategy for the synthesis of the corresponding silanol Si(C2F5)3OH, which readily condenses at room temperature to the hexakis(pentafluoroethyl)disiloxane, (C2F5)3SiOSi(C2F5)3. Deprotonation of Si(C2F5)3OH employing a sterically demanding phosphazene base allows the characterization of the first example of a dimeric triorganosilanolate: the dianionic hexakis(pentafluoroethyl)disilanolate, [{Si(C2F5)3O}2]2−, implies Lewis amphoteric character of the monomeric [Si(C2F5)3O]− anion. [ABSTRACT FROM AUTHOR]

As recently shown, the introduction of pentafluoroethyl functionalities into silicon compounds is of general interest due to an enhanced Lewis acidity of the resulting species. By this means, the synthesis of previously inaccessible hypervalent silicon derivatives is enabled. While an easy access to tris(pentafluoroethyl)silanes has already been published, synthetic strategies for the selective preparation of bis derivatives are yet unknown. In this contribution, a convenient protocol for the synthesis of functional bis(pentafluoroethyl)silicon compounds is presented. These compounds represent precursors for the synthesis of pentafluoroethylated polysiloxanes. Furthermore, they prove to be resistant to oxonium cations, which is a key feature for the preparation of stable pentafluoroethylsilic acids. Treatment of dichlorodiphenoxysilane with in situ generated pentafluoroethyl lithium leads to the corresponding bis(pentafluoroethyl)silane in high yields. (C2F5)2Si(OPh)2 serves as a starting material for further functionalized bis(pentafluoroethyl)silanes. These silanes have been isolated and their reactivity towards N bases studied. The pronounced Lewis acidity of the obtained compounds has been documented by the formation of octahedral adducts with nitrogen donors such as 1,10-phenanthroline and acetonitrile. [ABSTRACT FROM AUTHOR]

Fluorine, Oxidative Addition, Perfluorosilicates, Silanide Anion, Silicon Frontispiece: Oxidative Additions of C-F Bonds to the Silanide Anion [Si(C2F5)3]- Keywords: Fluorine; Oxidative Addition; Perfluorosilicates; Silanide Anion; Silicon EN Fluorine Oxidative Addition Perfluorosilicates Silanide Anion Silicon 1 1 1 04/14/22 20220419 NES 220419 B Silicon b In their Research Article (e202116468), Berthold Hoge et al. report oxidative additions of [Si(C SB 2 sb F SB 5 sb ) SB 3 sb ] SP - sp to aryl- and alkenylfluorides, enabling the isolation of tetraorganofluorosilicate salts devoid of chelating ligands. [Extracted from the article]

Silicon In their Research Article (e202116468), Berthold Hoge et al. report oxidative additions of [Si(C2F5)3]− to aryl‐ and alkenylfluorides, enabling the isolation of tetraorganofluorosilicate salts devoid of chelating ligands. [ABSTRACT FROM AUTHOR]

Keywords: Fluor; Oxidative Addition; Perfluorosilicate; Silanid-Anion; Silicium DE Fluor Oxidative Addition Perfluorosilicate Silanid-Anion Silicium 1 1 1 04/12/22 20220419 NES 220419 B Silicium b In ihrem Forschungsartikel (e202116468) berichten Berthold Hoge et al. über oxidative Additionen von [Si(C SB 2 sb F SB 5 sb ) SB 3 sb ] SP - sp an Aryl- und Alkenylfluoride, welche die Isolierung von Tetraorganofluorosilicatsalzen frei von chelatisierende Liganden ermöglichen. Frontispiz: Oxidative Addition von C-F-Bindungen an das Silanid-Anion [Si(C2F5)3]-. [Extracted from the article]