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Dalton Transactions

The international journal for inorganic, organometallic and bioinorganic chemistry



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Dalton Trans., 2008, 271 - 282, DOI: 10.1039/b713427d

Hypervalent hydridosilicates: synthesis, structure and hydride bridging

Paul D. Prince, Michael J. Bearpark, G. Sean McGrady and Jonathan W. Steed

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–HK 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–HK and Si–OK 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.

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