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

Abstract

The methyl–amide complex [TaCp*(NtBu)Me(NMe2)] (1a) was isolated by reaction of the chloro–methyl [TaCp*(NtBu)MeCl] complex with LiNMe2. Reaction of the mono-amide compounds [TaCp*(NtBu)XY] (X=NMe2, Y=Me (1a); X=NHtBu, Y=Me (1b), Cl (1c)) with CO2 gives the η2-carbamate derivatives [TaCp*(NtBu)(η2-O2CX)Y] (X=NMe2, Y=Me (2a); X=NHtBu, Y=Me (2b), Cl (2c)). A similar reaction with the di-amide complex [TaCp*(NtBu)(NHtBu)2] (1d) gives the di-carbamate derivative [TaCp*(NtBu){η2-O2C(NHtBu)}{η1-O2C(NHtBu)] (2d). Reaction of the methyl–carbamate (2a) with isocyanide CNAr (Ar=2,6-Me2C6H3) gives the η2-iminoacyl–η1-carbamate complex [TaCp*(NtBu){η2-C(Me)NAr}{η1-O2C(NMe2)] (3a). Formation of the related compound [TaCp*(NtBu){η2-C(Me)NAr}{η1-O2C(NHtBu)}] (3b) was only detected by NMR spectroscopy in C6D6 or CDCl3 whereas the reaction of 2b in hexane gives the η1-iminoacyl–η2-carbamate complex [TaCp*(NtBu){η1-C(Me)NAr}{η2-O2C(NHtBu)}] (3b′). All of the new compounds were characterized by elemental analysis and 1H- and 13C-NMR spectroscopy.