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

摘要

Starting from tetrakis(trimethylsilyl)stannane, the tris(trimethylsilyl)stannyl alkali derivatives (Me3Si)(3)SnM, (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 Li-7 and Sn-119 between [(Me3Si)(3)Sn](-) 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)(3)Sn](-) units are joined by a direct Sn-Na contact, 3.0775(18) angstrom in length. (c) 2005 Elsevier B.V. All rights reserved.