Trifluoromethylated Compounds with SiNN and SiON Backbone, and the Crystal Structures of Trimethyl- and Trichloro(trifluoromethyl)silane

The reaction of (F3C)Cl2SiCl3 with the lithiated hydrazine LiN(Me)NMe2 gives the compound (F3C)Cl2SiN(Me)NMe2 (1) and in traces Cl3SiN(Me)NMe2 (2). The reactions with LiN(SiMe3)NMe2 and LiONMe2 give (F3C)Cl2SiN(SiMe3)NMe2 (4) and (F3C)Cl2SiONMe2 (5), respectively. The compounds were characterised by multinuclear solution NMR, gas-phase IR spectroscopy and mass spectrometry. Information about conformational preferences of 1 and 4 can be extracted by comparing experimental IR spectra with those calculated by quantum chemical methods (B3LYP/6-311G**). The former show the gas phase of the β -donor-acceptor silanes 1 and 4 to be dominated by the anti conformations, while the calculations show a preference for the gauche conformers. The crystal structure of Cl3SiN(Me)NMe2 (2) has been determined. The solid-state structures of the Ruppert reagent F3C–SiMe3 (1) and its chlorine analogue F3C–SiCl3 (2) have also been determined by X-ray diffraction of single crystals grown by in situ techniques.