Prince Paul D, Bearpark Michael J, McGrady G Sean, Steed Jonathan W
Department of Chemistry, King's College London, Strand, London, UKWC2R 2LS.
Dalton Trans. 2008 Jan 14(2):271-82. doi: 10.1039/b713427d. Epub 2007 Oct 23.
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.
通过光谱、结构和计算方法制备并表征了一系列氢化硅酸盐阴离子。一般方法是在[18]冠醚-6存在下，使KH与中性硅烷前体反应。通过这种方式，稳定了Ph3SiH2（1）、Ph3SiF2（9）和(p-FC6H4)3SiHF/(p-FC6H4)3SiH2（12）的[K([18]冠醚-6)]+盐，并通过核磁共振光谱和X射线衍射对其进行了表征。在每种情况下，阴离子都采用三角双锥（TBP）几何构型，三个赤道面苯基与轴向Si-H/Si-F键重叠。Si-H···K距离以及对1的密度泛函理论计算表明，静电相互作用并不决定阴离子所采用的几何构型。同样以这种方式结晶出了H2SiOiPr3盐（7）；X射线衍射表明，在这种情况下，存在轴向氢化物配体的扭曲TBP排列，以及Si-H···K和Si-O···K相互作用。1H NMR交换实验表明1能与Ph3SiH轻松进行氢化物交换。化合物1对多种底物都是一种良好的氢化物转移试剂，但其高反应活性常常导致重新分布和其他副反应。
