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

The methyl-amide complex [TaCp*((NBu)-Bu-')Me(NMe2)] (1a) was isolated by r eaction of the chloro-methyl [TaCp*((NBu)-Bu-')MeCl] complex with LiNMe2. R eaction of the mono-amide compounds [TaCp*((NBu)-Bu-':)XY] (X = NMe2, Y = M e (1a), X = NH'Bu, Y=Me (1b), Cl (1c)) with CO2 gives the eta (2)-carbamate derivatives [TaCp*((NBu)-Bu-')(eta (2)-O2CX)Y] (X =NMe2, Y=Me (2a); X=(NHB u)-Bu-', Y = Me (2b), Cl (2c)). A similar reaction with the di-amide comple x [TaCp*((NBu)-Bu-')((NHBu)-Bu-')(2)] (1d) gives the di-carbamate derivativ e [TaCp*((NBu)-Bu-')( eta (2)-O2C((NHBu)-Bu-')) (eta (1)-O2C((NHBu)-Bu-')] (2d). Reaction of the methyl-carbamate (2a) with isocyanide CNAr (Ar = 2,6- Me2C6H3) gives the eta (2)-iminoacyl-eta (1)-carbamate complex [TaCp*((NBu) -Bu-')(eta (2)-C(Me)=NAr) (eta (1-) O2C(NMe2)] (3a). Formation of the relat ed compound [TaCp*((NBu)-Bu-')(eta (2)-C(Me)=NAr) (eta (1)-O2C((NHBu)-Bu-') )] (3b) was only detected by NMR spectroscopy in C6D6 or CDCl3 whereas the reaction of 2b in hexane gives the eta (1)-iminoacyl-eta (2)-carbamate comp lex [TaCp*((NBu)-Bu-')(eta (1)-C(Me)=NAr) (eta (2)-O2C((NHBu)-Bu-'))] (3b(' )). All of the new compounds were characterized by elemental analysis and H -1- and C-13-NMR spectroscopy. (C) 2001 Elsevier Science B.V. All rights re served.