N,N'-Dimethylcyclodisilazanes -SiMeR-NMe-SiMeR'-NMe- (R = R' = Me, Vi,
or Et and R = Me, R' = Vi, Et, or Ph where Vi = vinyl) have been prep
ared in good yield by cyclization of bis(methylamino)silanes with chlo
rosilanes. H-1, C-13, Si-29 and N-15 NMR spectra have been assigned. T
he four-membered cyclic structure of the compounds have been confirmed
by mass spectrometry and IR absorption measurements.