ChemInform Abstract: Hypervalent Octahedral SiH₆^2‐ Species from High‐Pressure Synthesis.

Abstract

Thermodynamically stable solids M2SiH6 (M: K, Rb) are prepared from mixtures of MH and Si, or MSi using ammonia borane as hydrogen source (NaCl capsule, 4—9 GPa, 400—700 °C, 1 h).

Calix[4]pyrrole Hydridosilicate: The Elusive Planar Tetracoordinate Silicon Imparts Striking Stability to Its Anionic Silicon Hydride

“…The Si−H bond is rather short (1.36 Å) in comparison to the previously reported structures (1.50−1.60 Å). 40,41,43 The calix [4]pyrrole ligand adopts a ruffled conformation, with two opposite methyl groups being identical, in agreement with the C 2v symmetry in solution as observed by 1 H NMR spectroscopy. The methyl groups block the coordination side trans to the Si−H bond.…”

“…The methyl-calix [4]pyrrole macrocyclic ligand, easily prepared in a one-step procedure, 44 was fully deprotonated with benzyl potassium in toluene at 120 °C (Scheme 1). Changing the solvent to acetonitrile and addition of HSiCl 3 at room temperature gave the potassium salt of methyl-calix [4]pyrrole hydridosilicate [1 − ][K + ] in 50% isolated yield at mmol scale.…”

“…The methyl-calix [4]pyrrole macrocyclic ligand, easily prepared in a one-step procedure, 44 was fully deprotonated with benzyl potassium in toluene at 120 °C (Scheme 1). Changing the solvent to acetonitrile and addition of HSiCl 3 at room temperature gave the potassium salt of methyl-calix [4]pyrrole hydridosilicate [1 − ][K + ] in 50% isolated yield at mmol scale. 45 The respective lithium and tetraphenyl phosphonium salts Multinuclear NMR spectroscopy revealed noticeable spectroscopic features of [1-H − ], being similar for the various cations.…”

“…It furthermore supports SET steps in the reduction chemistry with hydridosilicates. Finally, it introduces the calix [4]pyrrole ligand as new, 4-fold anionic platform for the emerging field of geometrically constrained main-group element species. 52…”

Unraveling Hidden Mg–Mn–H Phase Relations at High Pressures and Temperatures by in Situ Synchrotron Diffraction

“…We found that ammonia borane (BH 3 NH 3 ), with its high hydrogen capacity and well-defined two-step decomposition behavior under pressure (BH 3 NH 3 → (BH 2 NH 2 ) + H 2 ; (BH 2 NH 2 ) → BN + 2H 2 ) leading to inert residuals, 18 represents a superior internal hydrogen source for hydrogenations at gigapascal pressures. 36,37 NaCl is a popular capsule material since it provides tight seals in the case of air/moisture sensitive precursors and resists hydrogen diffusion. For in situ diffraction investigations there is an additional benefit because the wellknown EOS of NaCl 20 can be used for internal p, T calibration and the assessment of p, T conditions during experiments.…”