FURTHER REACTIONS OF THE AMINO(IMINO)BORA NE ME3SI(TBU)N-B=NTBU AND THE ALKYLIDENE(AMINO)BORANE ME3SI(TBU)-N=B=CHTBU

The alkylidenetantalum complexes [tBuHC=TaCl3(THF)2] (1b), [PhHC=TaCl3 (PMe3)2] (1c), and [tBuHC=Td(CH2tBu)3] (1d) were treated with the amin o(imino)borane Me3Si(t-Bu) N - B = NtBu (2d). From 1b and 2d, the alky lidene(amino) borane Me3Si(tBu)N = B = CHtBu (7) is formed by metathes is. The 1:2 reaction of 1c with 2d gives the azadiboracyclobutane [-N( tBu)-B(X)-CHPh-B(X)-] [6d, X = Me3Si(tBu)N]. The six-membered ring com pound [-N(tBu)=BR-N(tBu)SiMe2CH2TaR(CHtBu)-] (8, R = CH2tBu) is obtain ed from 1d and 2d; the product 8 crystallizes in the space group P2(1) /c. The borane 7 is attacked at the BC double bond by Et2NH, tBuCHO, a nd Me3SiN3 giving the diamino(neopentyl)borane 9 by protolysis, the ox aboracyclobutane 10 by [2 + 2] cycloaddition, and the azaboracycloprop ane 11 by cycloaddition and elimination of N2, respectively.