Syntheses and X-ray Structures of Base-Stabilized Iminoalanes§

Reactions between low-valent [Cp*Al]4 and trialkylsilyl azides RR‘2SiN3 proceed with N2 elimination and subsequent formation of iminoalanes [Cp*AlNSiRR‘2]x (R, R‘ = Et 1, i-Pr 2, t-Bu 3; R = t-Bu R‘ = Me 4), which further react with an equimolar amount of 4-(dimethylamino)pyridine (dmap) with formation of dmap-stabilized iminoalanes of the general type [dmap-Al(Cp*)NSiRR‘2]2 (R, R‘ = Et 5, i-Pr 6; R = t-Bu R‘ = Me 7). No reaction was observed for [Cp*AlNSi(t-Bu)3]2, 3. In contrast, Cp*Al and RR‘2SiN3 react in the presence of dmap at elevated temperatures with C−H activation of the ortho-Hdmap and formation of dihydroanthracene-type compounds of the type [o-Al(Cp*)N(H)SiRR‘2-dmap]2 (R, R‘ = Et 8, i-Pr 9, t-Bu 10; R = t-Bu R‘ = Me 11). The reaction of Cp*Al and t-Bu3SiN3 with 2 equiv of dmap proceeds with o-C−Hdmap activation of only one dmap molecule and formation of the dmap-stabilized monomeric aminoalane [o-Al(dmap)(Cp*)N(H)Si(t-Bu)3-dmap], 12. Compounds 3 and 5−12 were characterized by IR, mass, and mu...