Insertion of carbon dioxide and isocyanide into tantalum–amide and tantalum–methyl bonds

The methyl–amide complex [TaCp*(NBu)Me(NMe2)] (1a) was isolated by reaction of the chloro–methyl [TaCp*(NBu)MeCl] complex with LiNMe2. Reaction of the mono-amide compounds [TaCp*(N Bu)XY] (X=NMe2, Y=Me (1a); X=NHBu, Y=Me (1b), Cl (1c)) with CO2 gives the h-carbamate derivatives [TaCp*(NBu)(h-O2CX)Y] (X=NMe2, Y=Me (2a); X=NHBu, Y=Me (2b), Cl (2c)). A similar reaction with the di-amide complex [TaCp*(NBu)(NHBu)2] (1d) gives the di-carbamate derivative [TaCp*(NBu){h-O2C(NHBu)}{h-O2C(NHBu)] (2d). Reaction of the methyl–carbamate (2a) with isocyanide CNAr (Ar=2,6-Me2C6H3) gives the h-iminoacyl–h-carbamate complex [TaCp*(NBu){h-C(Me) NAr}{hO2C(NMe2)] (3a). Formation of the related compound [TaCp*(NBu){h-C(Me) NAr}{h-O2C(NHBu)}] (3b) was only detected by NMR spectroscopy in C6D6 or CDCl3 whereas the reaction of 2b in hexane gives the h-iminoacyl–h-carbamate complex [TaCp*(NBu){h-C(Me) NAr}{h-O2C(NHBu)}] (3b%). All of the new compounds were characterized by elemental analysis and Hand C-NMR spectroscopy. © 2001 Elsevier Science B.V. All rights reserved.