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Although the adduct of aluminum trichloride with thionyl chloride has been reported, no thionyl chloride adduct of a main group element Lewis acid or organometallic compound has been structurally characterized. In this communication we present the synthesis and reactivity of the structurally ascertained adduct of thionyl chloride with tris(pentafluoroethyl)gallane as a representative of a main group element Lewis acid. Gallium and indium compounds with electron withdrawing groups, e.g. the pentafluoroethyl ligand, display versatile properties. While gallates and indates, [MR 4 ] - , behave as weakly coordinating anions, neutral gallanes and indanes, MR 3 , are strong Lewis acids. Salts with the tetrakis(pentafluoroethyl)gallate and -indate, [M(C 2 F 5 ) 4 ] - (M=Ga, In), have recently been studied in detail. In contrast to this, work on the syntheses of the free Lewis superacids M(C 2 F 5 ) 3 (M=Ga, In) is scarce and underdeveloped. The hydrates [M(C 2 F 5 ) 3 (OH 2 ) 2 ] proved to be suitable starting materials, particularly due to their thermal stability. Herein we report on synthesis and characterization of reactive adducts, [M(C 2 F 5 ) 3 D], with the weak donor molecules (D) SOCl 2 and Me 3 SiF. The effective Lewis acidities of Ga(C 2 F 5 ) 3 and In(C 2 F 5 ) 3 were experimentally determined by the (modified) Gutmann-Beckett method and their catalytic potential is showcased., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

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(C 2 F 5 ) 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., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

According to a first view on the geometrical and electronic structure of the tris(pentafluoroethyl)silanide, this anion appears as a Lewis base. Quantum chemical calculations on perfluoroalkylated silanides show significantly lower HOMO and LUMO energy levels in comparison to their non-fluorinated counterparts, which implies reduced Lewis basicity and increased Lewis acidity of the [Si(C 2 F 5 ) 3 ] - ion. With these findings and a HOMO-LUMO gap of 4.80 eV similar to N-heterocyclic silylenes (NHSis), perfluoroalkyl silanides are predestined to exhibit Lewis-amphoteric character similar to silylenes. Deprotonation of Si(C 2 F 5 ) 3 H with sterically demanding phosphazene bases afforded thermally stable phosphazenium salts of the [Si(C 2 F 5 ) 3 ] - anion, which add to benzaldehyde, benzophenone, CS 2 , and CO 2 in various manners. This behavior also mirrors the reactivity of silylenes towards ketones as well as heterocumulenes and is rationalized by Lewis amphotericity being inherent in these silanides., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We report on the first examples of isolated silanol-silanolate anions, obtained by utilizing weakly coordinating phosphazenium counterions. The silanolate anions were synthesized from the recently published phosphazenium hydroxide hydrate salt with siloxanes. The silanol-silanolate anions are postulated intermediates in the hydroxide-mediated polymerization of aryl and alkyl siloxanes. The silanolate anions are strong nucleophiles because of the weakly coordinating character of the phosphazenium cation, which is perceptible in their activity in polysiloxane depolymerization., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The reaction of a strongly basic phosphazene (Schwesinger base) with water afforded the corresponding metastable hydroxide trihydrate [OH(OH 2 ) 3 ] - salt. This is the first hydroxide solvate that is not in contact with a cation and furthermore one of rare known water-stabilized hydroxide anions. Thermolysis in vacuum results in the decomposition of the hydroxide salt and quantitative liberation of the free phosphazene base. This approach was used to synthesize the Schwesinger base from its hydrochloride salt after anion exchange in excellent yields of over 97 %. This deprotonation method can also be used for the phosphazene-base-catalyzed preparation of the Ruppert-Prakash reagent Me 3 SiCF 3 using fluoroform (HCF 3 ) as the trifluoromethyl building block and sodium hydroxide as the formal deprotonation agent., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Weakly coordinating anions (WCAs) are important for academic reasons as well as for technical applications. Tetrakis(pentafluoroethyl)gallate, [Ga(C 2 F 5 ) 4 ] - , a new WCA, is accessible by treatment of [GaCl 3 (dmap)] (dmap=4-dimethylaminopyridine) with LiC 2 F 5 . The anion [Ga(C 2 F 5 ) 4 ] - proved to be reluctant towards deterioration by aqueous hydrochloric acid or lithium hydroxide. Various salts of [Ga(C 2 F 5 ) 4 ] - were synthesized with cations such as [PPh 4 ] + , [CPh 3 ] + , [(O 2 H 5 ) 2 (OH 2 ) 2 ] 2+ , and [Li(dec) 2 ] + (dec=diethyl carbonate). Thermolysis of [(O 2 H 5 ) 2 (OH 2 ) 2 ][Ga(C 2 F 5 ) 4 ] 2 gives rise to a dihydrate of tris(pentafluoroethyl)gallane, [Ga(C 2 F 5 ) 3 (OH 2 ) 2 ]. All products were characterized by NMR and IR spectroscopy, mass spectrometry, X-ray diffraction, and elemental analysis. Furthermore, an outlook for the application of [Li(dec) 2 ][Ga(C 2 F 5 ) 4 ] as a conducting salt in lithium-ion batteries is presented., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The tris(pentafluoroethyl)silanide anion is accessible by the deprotonation of Si(C 2 F 5 ) 3 H 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(C 2 F 5 ) 3 ] as a powerful nucleophilic transfer reagent., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Tris(pentafluoroethyl)silane, which is conveniently accessible by the treatment of Si(C 2 F 5 ) 3 X (X=Cl, Br) with Bu 3 SnH, was successfully employed for hydrosilylation reactions. In the presence of a palladium catalyst, hydrosilylation of phenylacetylene with Si(C 2 F 5 ) 3 H affords the product of an α-addition whereas the reaction of trimethylsilylacetylene with the silane leads to the β-trans product. Tris(pentafluoroethyl)silane can be deprotonated by sterically demanding bases such as lithium diisopropylamide at low temperatures to give the corresponding silanide ion. The addition of crown ethers or cryptands to this highly reactive species enabled the isolation and characterization of salt-like tris(pentafluoroethyl)silanide at room temperature., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Pure anhydrous hexafluorosilicic acid (H 2 [SiF 6 ]) 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(C 2 F 5 ) n X 4-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., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The synthesis of the germylene phosphane adduct (C2 F5 )2 Ge⋅PMe3 is described. Starting from (C2 F5 )3 GeH in an excess of PMe3 , heating was applied, whereupon reductive elimination of C2 F5 H occurred. The molecular structure was ascertained by X-ray diffraction and compared with information obtained by quantum chemical methods. The ligand properties were derived by studying the IR spectrum of the nickel(0) complex [Ni(CO)3 {Ge(C2 F5 )2 (PMe3 )}] in the CO region. (C2 F5 )2 Ge⋅PMe3 turned out to be a π-accepting ligand comparable to PMe3 , in terms of Tolman's electronic parameter. Furthermore a [2+4] cycloaddition reaction with 2,3-dimethyl-1,3-butadiene, and σ-bond insertion reactions were recorded. Activation of the C-Cl bond in dichloromethane gives rise to the formation of the phosphonium ylide complex [(C2 F5 )2 Cl2 Ge-CH2 PMe3 ], which was fully characterized by X-ray diffraction., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Chlorosilicates represent important intermediates in S(N)2 reactions of chlorosilanes. They can be stabilized by the introduction of electron-withdrawing substituents. Salts of various (pentafluoroethyl)chlorosilicates have been isolated and structurally characterized., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Lithium carbenoids are versatile compounds for synthesis owing to their intriguing ambiphilic behavior. Although this class of compounds has been known for several years, few solid-state structures exist because of their high reactivity and often low thermal stability. Using cryo X-ray techniques, we were now able to elucidate the first solid-state structure of a Li/F alkyl carbenoid, pentafluoroethyllithium (LiC2F5), finally yielding a prototype for investigating structure-reactivity relationships for this class of molecules. The compound forms a diethyl ether-solvated dimer bridged by a rare C-F-Li link. Complementary NMR spectroscopy studies in solution show dynamic processes and indicate rapid exchange of starting material and product. Theoretical investigations help to understand the formation of the observed unusual structural motif., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The synthesis and complete characterization of functional, highly Lewis acidic tris(pentafluoroethyl)silanes as well as tetrakis(perfluoroalkyl)silanes Si(C2F5)4 and Si(C2F5)3 CF3 by direct fluorination is described. The reaction of SiCl4 with LiC2F5 invariably affords (pentafluoroethyl)fluorosilicates. To avoid silicate formation by fluoride transfer from LiC2F5 the Lewis acidity of the silane has to be decreased by electron-donating substituents, such as dialkylamino groups. The easily accessible Si(C2F5)3 NEt2 is a valuable precursor for a series of tris(pentafluoroethyl)silanes., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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(C2 F5 )3 F3 ](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(C2 F5 )3 F3 ] and [PPh4 ][Si(C2 F5 )3 F2 ] along with the precursor [H(OEt2 )2 ][Si(C2 F5 )3 F2 ] was achieved from SiCl4 and LiC2 F5 ., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)