BIS(CHLOROMETHYLSILYL)AMINE AND BIS(CHLOROMETHYLSILYL)METHYLAMINE - PREPARATION, REACTIVITY AND SPECTROSCOPIC STUDIES OF THEIR STEREOISOMERS AND CONFORMERS

The compounds NH(SiHMeCl)(2) 1 and NMe(SiHMeCl)(2) 2 have been prepare d by treating SiHMeCl2 with CaCl2 . 8NH(3) and NH2Me respectively. Eac h was characterised by elemental analysis, mass spectrometry, NMR and IR spectroscopy. Dipole moments were also measured. The NMR spectra in dicate that both compounds form 1 : 1 mixtures of the rac and meso dia stereomers, their abundances corresponding to a statistically controll ed synthetic pathway. The NMR and mass spectra also show that 1,5-dich loro-1,2,3,4,5-pentamethyltrisilazane, SiHMe[NMe(SiHMeCl)](2) 3, which is formed as a side product in the synthesis of 2, also consists of t wo diastereomers. Variable-temperature H-1 NMR spectra of NH(SiHMeCl)( 2) indicate participation of H(N) in hydrogen bonding. The compound is decomposed by heat and reacts with pyridine to form NH4Cl, SiHMeCl2 a nd polysilazanes, whereas NMe(SiHMeCl)(2) shows only slight decomposit ion up to 80 degrees C and does not react with pyridine. Infrared spec tra in the v(SiH) region are interpreted in terms of the results of ab initio calculations of frequency, intensity and conformer abundance. The two bands near 2200 cm(-1) in the spectrum of 2 have their origin in two effects: different orientations of the Si-H bonds relative to t he Si-N-Si plane in several conformers and an unprecedented strong dip ole-dipole coupling between the two Si-H bond stretching motions in si tuations where the bonds are roughly parallel. The absence of such an observed splitting for 1 is likely to be due in part to signal averagi ng during a free internal rotation. Significant couplings are also cal culated to occur between Si-Cl bond-stretching motions, whose source m ust be different from that for the Si-H bond stretches.