Solid-State NMR and DFT Studies on the Formation of Well-Defined Silica-Supported Tantallaaziridines: From Synthesis to Catalytic Application.

Single-site, well-defined, silica-supported tantallaaziridine intermediates [≡Si-O-Ta(η(2) -NRCH2 )(NMe2 )2 ] [R=Me (2), Ph (3)] were prepared from silica-supported tetrakis(dimethylamido)tantalum [≡Si-O-Ta(NMe2 )4 ] (1) and fully characterized by FTIR spectroscopy, elemental analysis, and (1) H,(13) C HETCOR and DQ TQ solid-state (SS) NMR spectroscopy. The formation mechanism, by ß-H abstraction, was investigated by SS NMR spectroscopy and supported by DFT calculations. The C-H activation of the dimethylamide ligand is favored for R=Ph. The results from catalytic testing in the hydroaminoalkylation of alkenes were consistent with the N-alkyl aryl amine substrates being more efficient than N-dialkyl amines.