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Syntheses and Structures of the First Heavy Alkaline Earth Metal Bis(tris(trimethylsilyl))silanides

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journal contribution
posted on 24.05.2004 by Weijie Teng, Karin Ruhlandt-Senge
The first heavy alkaline earth metal bis(tris(trimethylsilyl))silanides were obtained in high yield and purity by a straightforward metathesis reaction involving the treatment of potassium tris(trimethylsilyl)silanide, K(THF)nSi(SiMe3)3, with calcium, strontium, and barium iodides. The addition of specific donors provided either contact or separated species in the solid state, whereas in aromatic solvents the compounds dissociate into separated ions, as shown by 29Si NMR spectroscopic studies. We here report on the syntheses and characterization of compounds displaying M−Si bonds in the solid state with the general formula of M(THF)n(Si(SiMe3)3)2 (M = Ca, n = 3, 1; Sr, n = 3, 2; and Ba, n = 4, 3) and Sr(TMEDA)(THF)(Si(SiMe3)3)2, 4 (TMEDA = N,N,N‘,N‘-tetramethylethylenediamine). Compound 5, [Ba(HMPA)6][(Si(SiMe3)3)2], displays separated ions, while 6, [Ba(18-crown-6)(Si(SiMe3)3)2][Ba(HMPA)6][(Si(SiMe3)3)2], is a rare example containing both contact and separated ions in the asymmetric unit. All compounds were characterized using X-ray crystallography, 1H, 13C, and 29Si NMR, and IR spectroscopy.