Tris(trimethylsilyl)stannyl alkali derivatives: Syntheses and NMR spectroscopic properties

Starting from tetrakis(trimethylsilyl)stannane, the tris(trimethylsilyl)stannyl alkali derivatives (Me3Si)3SnM, (M = Li, Na, K, Rb, Cs) were prepared in excellent yields. Reaction with MgBr2 · Et2O afforded bis[tris(trimethylsilyl)stannyl]magnesium. Reaction products were investigated by means of multinuclear NMR spectroscopy. At low temperatures, coupling of 7Li and 119Sn between [(Me3Si)3Sn]− and [Li · 3THF]+ (337 Hz) or [Li · 12Cr4]+ (275 Hz), was observed. NMR chemical shifts and coupling constants of the stannyl anions exhibit a strong dependency on the nature of the cation, solvent system, concentration and temperature. In addition, the molecular structure of tris(trimethylsilyl)stannyl sodium · 15Cr5 was determined by X-ray crystallography. The [Na · 15Cr5]+ and [(Me3Si)3Sn]− units are joined by a direct Sn–Na contact, 3.0775(18) Å in length.