Studies of silylfurans, furylsilanes, and silylthiophenes: Structure of 2,5-disilylthiophene

2-Silyl- and 2,5-disilylfuran (2-H₃SiC₄H₃O, 2,5-(H₃Si)₂C₄H₂O) have been obtained from furan by lithiation with ^tBuLi, followed by treatment with H₃SiBr at very low temperatures (-196 to -80°C) in diethyl ether, as distillable liquids (bp 72 and 108°C, respectively). Di-2-furyl- and tri-2-furylsilane ((2-C₄H₃O)_nSiH_4-n, n = 2, 3) are the products of the reaction of 2-furyllithium with Si(OMe)₄, followed by reduction using LiAlH₄ in diethyl ether/ tetrahydrofuran. The methoxysilane precursors (2-C₄H₃O)_nSi(OMe)_4-n (n = 2, 3) have also been isolated. The analogous reactions of (MeO)₄Si with equivalent quantities of (a) lithiated thiophenes and (b) LiAlH₄ gave 2-silyl- and 2,5-disilylthiophene. Comprehensive NMR data have been compiled for all compounds, and the composition was confirmed by mass spectrometry. The crystal and molecular structure of 2,5-disilylthiophene has been determined by low-temperature "in situ" single-crystal X-ray diffraction, and ab initio calculations (MP2/6-31G*) have been carried out for this compound and the corresponding disilylfuran. The experimental and theoretical results are in excellent agreement and show that there are no silicon-induced irregularities as compared to methylated furans or thiophenes. Minor conformational differences can be ascribed to packing forces in the crystal. Low-temperature solution NMR experiments have shown that there is no aggregation via intermolecular donor-acceptor interactions in these systems.