High-Pressure Freezing, Crystal Structure Studies and Si-CF3 Bond Polarizability of Trimethyl(trifluoromethyl)silane (Postprint)

摘要

Trimethyl(trifluoromethyl)silane, (CH3)3SiCF3, has been in situ pressure frozen in a diamond anvil cell and its structure determined at 0.90(5) GPa/296 K by single-crystal X-ray diffraction. The crystal is monoclinic, space group P21/m, with the molecules lying on crystallographic mirror planes. The CH3 and CF3 groups assume the fully staggered conformation. The 14-fold coordination scheme of the molecules is similar to those in (CH3)3SiCl polymorphs, but different from that in crystalline tetramethylsilane, (CH3)4Si (TMS). The longest Si-C bond length of 1.943(12) angstrom observed in the crystal structure has been documented. The shortest intermolecular contacts in the structure of pressure-frozen CF3Si(CH3)3 are observed between the hydrogen atoms, and those involving fluorine atoms are longer than sums of van der Waals' radii. These structural features explain the facile cleavage of Si-CF3 bond for CF3 group transfer in organic reactions.