DEHYDROCOUPLING OF AMMONIA AND SILANES CATALYZED BY DIMETHYLTITANOCENE

The reactions of diphenylmethylsilane and of phenylmethylsilane with ammonia, to give the disilazanes, are effectively catalyzed by dimethyltitanocene (DMT). At longer reaction times, 1,3-dimethyl-1,3-diphenyldisilazane reacts further with excess ammonia to give short oligomers, e.g. (MePhHSiNH)3 and H(MePhHSiNH)(n)H (n = 2, 3), but high polymers cannot be made due to the low reactivities of the oligomers. The reactions of primary silanes with ammonia in the presence of DMT are unexpectedly slower than those of tertiary and secondary silanes. In these reactions homodehydrocoupling competes effectively with the amination reaction and physical properties indicate that the products are poly(aminosilanes) (RSiNH2)n, rather than the expected polysilazanes. Some preliminary results on the pyrolysis of poly(methylaminosilane) are reported.