Hypervalent Octahedral SiH₆²⁻Species from High‐Pressure Synthesis

Abstract

High‐pressure conditions afford unique all‐hydrido hypervalent complexes [SiH6]2− in the crystalline hydridosilicates A2SiH6 (A=K, Rb). Compared to normal‐valent silanes the SiH bond appears considerably enlarged, by about 0.15 Å. Accordingly, SiH stretching frequencies are drastically reduced, by about 400–500 cm−1, thus reflecting the weakness of a hypervalent SiH bond.

Formation and Reactivity of a Hexahydridosilicate [SiH6]2− Coordinated by a Macrocycle‐Supported Strontium Cation

“…[6] For the computationally optimized structure of K 2 SiH 6 , SiÀ H bond lengths of 1.62 Å were reported. [5] DFT calculations (B3PW91 functional) including dispersion corrections were carried out to describe the bonding in complex 3 a. The optimized structure is in fair agreement with the experimental one (see Supporting Information) with the SrÀ H bonds well reproduced (2.42 Å).…”

Identification of a Simplest Hypervalent Hydrogen Fluoride Anion in Solid Argon

“…Despite some criticism of the term and concept of hypervalency, hypervalent species of the second-row elements 22–24 and hypervalent all-hydrido species 25, 26 have rarely been observed experimentally. We produced hydrogen fluoride anions in an argon matrix by electron bombardment of excess Ar containing a small proportion of methyl fluoride during matrix deposition.…”

A quantitative definition of hypervalency

“…The SiH 6 2– anion has been obtained as its K + and Rb + salts from high pressure synthesis. 15 Although this ion could be considered as hypervalent, the present analytical method gave γ (Si) = 2.78 for the naked anion. This is consistent with the fact that H is more electronegative than Si ( Χ = 2.20 and 1.90 respectively), giving the H atoms hydride character in this species.…”

“…This is consistent with the fact that H is more electronegative than Si ( Χ = 2.20 and 1.90 respectively), giving the H atoms hydride character in this species. For comparison, the published 15 QTAIM analysis of K 2 SiH 6 leads to γ (Si) = 3.00. Similarly, the [Ph 3 SiH 2 ] – anion gives γ (Si) = 2.57, consistent with experimental and computational characterization which revealed a hydridic character.…”