PUB - Publikationen an der Universität Bielefeld

The simple silylhydrazines F3SiN(Me)NMe2 (1), FSi(N(Me)NMe2)(2) (2), and F3SiN(SiMe3)NMe2 (3) have been prepared by reaction of SiF4 with LiN(Me)NMe2 and LiN(SiMe3)NW2, while F3SiN(SnMe3)NMe2 (4) was prepared from SiF4 and (Me3Sn)(2)NNMe2 (5). The compounds were characterized by gas-phase IR and multinuclear NMR spectroscopy (H-1, C-13, N-14/15, F-19, Si-29, Sn-119), as well as by mass spectrometry. The crystal structures of compounds 1-5 were determined by X-ray crystallography. The structures of free molecules I and 3 were determined by gas-phase electron diffraction. The structures of 1, 2, and 4 were also determined by ab initio calculations at the MP2/6-311 + G** level of theory. These structural studies constitute the first experimental proof for the presence of strong Si...N beta-donor-acceptor bonds between the SiF3 and geminal NMe2 groups in silylhydrazines. The strength of these non-classical Si...N interactions is strongly dependent on the nature of the substituent at the alpha-nitrogen atom of the SiNN unit, and has the order 3>4>1. The valence angles at these extremely deformed alpha-nitrogen atoms, and the Si...N distances are (crystal/gas): 1 104.2(1)/106.5(4)degrees, 2.438(1)/2.510(6) Angstrom; 3 83.6(1)/84.9(4)degrees, 2.102(1)/2.135(9) Angstrom; 4 89.6(1)', 2.204(2) Angstrom.