Hypervalent hydridosilicates: synthesis, structure and hydride bridging

Abstract

A range of hydridosilicate anions has been prepared and characterised by spectroscopic, structural and computational methods. The general approach involved reaction of KH with a neutral silane precursor in the presence of [18]crown-6. In this manner, [K([18]crown-6)]+ salts of [Ph3SiH2](-) (1), [Ph3SiF2](-) (9), and [(p-FC6H4)3SiHF](-)/[(p-FC6H4)3SiH2](-) (12) were stabilised and characterized by NMR spectroscopy and X-ray diffraction. In each case, the anion adopts a trigonal bipyramidal (TBP) geometry with three equatorial phenyl groups eclipsing the axial Si-H/Si-F bonds. The Si-H[dot dot dot]K distances, along with DFT calculations on 1, indicate an electrostatic interaction that does not dictate the geometry adopted by the anion. A [H2SiOiPr3](-) salt (7) has also been crystallised in the same way; X-ray diffraction shows in this case a distorted TBP array with axial hydride ligands, and both Si-H[...]K and Si-O[...]K interactions. 1H NMR exchange experiments show 1 to undergo facile hydride exchange with Ph3SiH. Compound 1 acts as a good hydride transfer reagent to a variety of substrates, but its high reactivity often results in redistribution and other side reactions.

Transition‐Metal‐Free Catalytic Hydrodefluorination of Polyfluoroarenes by Concerted Nucleophilic Aromatic Substitution with a Hydrosilicate

“…Fluorohydrosilicate A can generate difluorosilicate B and dihydrosilicate C through ar edistribution. [15] TheH DF proceeded smoothly to afford 2a (96 %) and the difluorosilicate K + [18-crown-6]Ph 3 SiF 2 À along with Ph 3 SiH and probably KF.T hese results suggest that the present HDF reaction involves the generation of hydrosilicates. We next examined the stoichiometric reaction of 1a with the dihydrosilicate K + [18-crown-6]Ph 3 SiH 2 À (1.0 equiv);S cheme 4c).…”

“…[13][14][15] In fact, facile catalytic hydrosilylation reactions of aldehydes and ketones have been achieved by hydride transfer from hydrosilicates generated from hydrosilanes and fluoride salts. [13][14][15] In fact, facile catalytic hydrosilylation reactions of aldehydes and ketones have been achieved by hydride transfer from hydrosilicates generated from hydrosilanes and fluoride salts.…”

“…On the other hand, the same reaction in the presence of as mall amount of water afforded hydrogen and Ph 3 SiOSiPh 3 (Scheme 4a,bottom), [14a] which was not observed in the absence of TBAT.T hese results suggest that the combination of Ph 3 SiH and TBAT generates highly reactive hydrosilicates (Scheme 4b). [15,17] DFT calculations with the Grimme DFT-D3 London dispersion correction with Becke-Johnson damping (D3BJ) [18] indicates aq ualitative trend that equilibrium is possible between the different forms (estimated DG = 9.5 kJ mol À1 at 298 K). [15,17] DFT calculations with the Grimme DFT-D3 London dispersion correction with Becke-Johnson damping (D3BJ) [18] indicates aq ualitative trend that equilibrium is possible between the different forms (estimated DG = 9.5 kJ mol À1 at 298 K).…”

A study on the deoxygenation of trialkyl‐, dialkyl‐phenyl‐ and alkyl‐diphenyl phosphine oxides by hydrosilanes

“…The reactions were carried out in a 300‐W CEM Discover focused microwave reactor equipped with a pressure controller applying 50‐80 W under isothermal conditions. Silanes 3 ‐ 5 and 7 are available commercially, while silanes 6 , 8‐10 , and 16‐19 were prepared by LiAlH 4 reduction of the corresponding chlorosilanes in accord with literature procedures . Compound 9 may also be synthesized by a known procedure .…”

Reaction ofo‐(HSiR2)(BMes2)C6H4with a fluoride ion: Fluoride attack at silicon and hydride transfer from silicon to boron to form FSi⋅⋅⋅HB interaction

“…However, isolation of the fluoro(hydrido)silicates is rather troublesome because they tend to undergo redistribution to form dihydridosilicates [R 3 [4]. The other is 1-(dimethylfluorosilane)-8-(9H-xanthene)naphthalenediyl, in which the silicon atom is pentacoordinate due to an agostic F Si· · ·H CR 3 interaction [6].…”