Salts of Tris(pentafluoroethyl)silylchalcogenolates [Si(CF)E] with E = S, Se, and Te: Synthesis, Structure, and Reactivity.

Unlike silanolates [SiRO] (R = alkyl, aryl), which have been intensely studied, the heavier derivatives [SiRE] (E = S, Se, Te) have been much less examined. Among such species, virtually nothing is known about perfluoroalkyl-substituted silylchalcogenolates. In this contribution, a convenient synthesis of tris(pentafluoroethyl)silylchalcogenolate salts [{(EtN)P═N}PN(H)Bu][Si(CF)E] (E = S, Se, Te; Bu = -butyl) is presented.

Tris(pentafluoroethyl)silanol Derivatives and the Lewis Amphoteric Tris(pentafluoroethyl)silanolate Anion, [Si(C F ) O].

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(C F ) ] , 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(C F ) O] .

Non-classical polyinterhalides of chlorine monofluoride: experimental and theoretical characterization of [F(ClF)].

We present the synthesis and characterization of the first non-classical Cl(i) polyinterhalide [NMe][F(ClF)] as well as the homologous polychloride [NPrMe][Cl]. Both salts were obtained from the reaction of the corresponding ammonium chlorides with ClF or Cl, respectively. Quantum-chemical investigations predict an unexpected planar structure for the [F(ClF)] anion.

Investigation of Large Polychloride Anions: [Cl ] , [Cl ] , and [Cl ].

For decades the chemistry of polyhalides was dominated by polyiodides and more recently also by an increasing number of polybromides. However, apart from a few structures containing trichloride anions and a single report on an octachloride dianion, [Cl ] , polychlorine compounds such as polychloride anions are unknown. Herein, we report on the synthesis and investigation of large polychloride monoanions such as [Cl ] found in [AsPh ][Cl ], [PPh ][Cl ], and [PNP][Cl ]⋅Cl , and [Cl ] obtained in [PNP][Cl ].

The Tris(pentafluoroethyl)silanide Anion.

Tris(pentafluoroethyl)silane, which is conveniently accessible by the treatment of Si(C F ) X (X=Cl, Br) with Bu SnH, was successfully employed for hydrosilylation reactions. In the presence of a palladium catalyst, hydrosilylation of phenylacetylene with Si(C F ) 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.

Nucleophilic Transfer Reactions of the [Si(C F ) ] Moiety.

The tris(pentafluoroethyl)silanide anion is accessible by the deprotonation of Si(C F ) 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 F ) ] as a powerful nucleophilic transfer reagent.

Pentafluoroethylsilicic Acids.

Pure anhydrous hexafluorosilicic acid (H [SiF ]) 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.

Synthesis of Functional Bis(pentafluoroethyl)silanes (C F ) SiX , with X=H, F, Cl, Br, OPh, and O CCF.

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.

Synthesis of chlorosilicates.

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.