Insertion Reaction of a Silylene into a N-H Bond of Hydrazine and a [1+4] Cycloaddition with Diphenyl Hydrazone

The reaction of a stable six-membered N-heterocyclic silylene, LSi (1) [L = CH{(C=CH2)(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}], with hydrazine and its derivatives is described. 1 reacts with hydrazine to form LSi(H)NHNH2 (2) under N-H bond insertion of the silylene. The reaction of 1 and N-methyl hydrazine results exclusively in the formation of LSi(H)NHNHMe (3). Treatment of 1 with an equimolar amount of diphenyl hydrazone in toluene yields the dearomatized siloxy-indolin-1-amine 4 in almost quantitative yield rather than the insertion product at the N-H bond of the NH2 group. Compounds 2-4 were characterized by microanalysis, multinuclear NMR, and IR spectroscopy. Compounds 2 and 4 are confirmed by X-ray structural analysis with the result that 2 and 4 are both monomeric and the silicon center of each resides in a distorted tetrahedral environment.