The Influence of Weakly Coordinating Cations on the O−H⋅⋅⋅O⁻ Hydrogen Bond of Silanol‐Silanolate Anions

Abstract

The reaction of a saline phosphazenium hydroxide hydrate with siloxanes led to a novel kind of silanol‐silanolate anions. The weakly coordinating behavior of the cation renders the formation of silanol‐silanolate hydrogen bonds possible, which otherwise suffer from detrimental silanolate–oxygen cation interactions. We investigated the influence of various weakly coordinating cations on silanol‐silanolate motifs, particularly with regard to different cation sizes. While large cations favor the formation of intramolecular hydrogen bonds resulting in cyclic structures, the less bulky tetramethyl ammonium cation encourages the formation of polyanionic silanol‐silanolate chains in the solid state.

Phosphorus‐Containing Superbases: Recent Progress in the Chemistry of Electron‐Abundant Phosphines and Phosphazenes

“…Recently, we were able to trap a row of such saline phosphazenium salts formed by the deprotonation of protic additives and elucidated their structures. This allows significant insights into the nature of formed “naked” anions and the partially necessity of stabilization via hydrogen bonding, as presented in more detail for silanol‐silanolate anions,[ 154 , 155 ] non‐coordinated phenolate anions and their phenol‐phenolate adducts. [156]…”

“…Recently, we were able to trap a row of such saline phosphazenium salts formed by the deprotonation of protic additives and elucidated their structures. This allows significant insights into the nature of formed "naked" anions and the partially necessity of stabilization via hydrogen bonding, as presented in more detail for silanol-silanolate anions, [154,155] noncoordinated phenolate anions and their phenol-phenolate adducts. [156] The hydroxide trihydrate anion, [OH(OH 2 ) 3 ] À , obtained by the reaction of water with the perethyl tetraphosphazene base [(Et 2 N) 3 P=N] 3 P=NtBu (18c, Scheme 19), represents the first hydroxide hydrate devoid of significant cation-anion interactions (Figure 2, top) and thus, contains three water molecules bonded via hydrogen bridges.…”

Photochemical Activation of Sulfur Hexafluoride: A Tool for Fluorination and Pentafluorosulfanylation Reactions

“…58 The activation of SF 6 by non-coordinated phenolate anions was reported in 2021 by Hoge and co-workers, resulting in the formation of phosphazenium pentafluorosulfanylide salts. 59 SF 6 can be completely deconstructed by electrochemical reduction (Magnier et al), 60 or by an aluminum(I) compound according to Crimmins et al 61 (Scheme 1 ).…”

Negative-ion field desorption revitalized by using liquid injection field desorption/ionization-mass spectrometry on recent instrumentation

“…Furthermore, 3trifluormethyl-phenol (5), dichloromethane (6), both Sigma-Aldrich (Steinheim, Germany), iodine (7, Merck KGaA, Darmstadt, Germany), polyethylene glycol diacid (average molecular weight 600 u) (8), perfluorononacoic acid (9), both Sigma-Aldrich (Steinheim, Germany), and a dishwashing detergent containing anionic surfactants (Pril Kraftgel, 10) were used. A sample of solid tetraphosphazene silanol-silanolate (11) was obtained from B. Hoge (Bielefeld University, Bielefeld, Germany) and dissolved in dry tetrahydrofuran [38]. Two samples of bis(catecholato)silanes (12 and 13) were obtained from L. Greb (Heidelberg University, Heidelberg, Germany) [39].…”

“…Handling of silanol-sinalolates requires the strict exclusion of moisture to avoid decomposition of these compounds, and thus, mass spectral characterization of the silanolate ion as well as elemental analysis of the ion pair was still missing, because the ion pair could neither be characterized by elemental analysis nor by any ionization technique in mass spectrometry so far [38]. Thus, a solution of tetraphosphazene silanolsilanolate (11) ), was prepared in dry THF and was analyzed by negative-ion as well as positive-ion LIFDI-MS using the Waters Micromass Q-TOF instrument (Fig.…”