Facile Preparation of a Scandium Terminal Imido Complex Supported by a Phosphazene Ligand

The scandium bis(alkyl) complex bearing the phosphazene ligand (LSc)-Sc-1(CH2SiMe3)(2) (1) (L-1 = N(PPh2=NPh)(2)) reacted with an equimolar amount of 2,6-diisopropylaniline to afford the corresponding mixed alkyl/anilido complex (LSc)-Sc-1[NHC6H3(Pr-i)(2)](CH2SiMe3) (2). Under mild conditions (20 degrees C, 4 h or 0 degrees C, 12 h), complex 2 could be swiftly transformed to the terminal imido complex (LSc)-Sc-1=N[C6H3(Pr-i)(2)](DMAP)(2) (4) in the presence of DMAP (DMAP = 4-N,N-dimethylaminopyridine). Correspondingly, treatment of the yttrium and lutetium bis(alkyl) complexes L(2)Ln(CH2SiMe3)(2) (L-2 = N [Ph2PNC6H3(Pr-i)(2)](2); Ln = Y (7), Lu (8)) with equimolar amounts of 2,6-diisopropylaniline gave the mixed alkyl/anilido complexes L(2)Ln[NHC6H3(Pr-i)(2)](CH2SiMe3) (Ln = Y (9), Lu (10)), which, however, underwent dealkylation of the Ln CH2SiMe3 species at temperatures of 60 degrees C for 9 and 100 degrees C for 10 to afford bis(anilido) complexes L(2)Ln[NHC6H3(Pr-i)(2)](2) (Ln = Y (11), Lu (12)) as redistribution products. All these complexes have been characterized by H-1, C-13{H-1}, and P-31{H-1} NMR spectroscopy and X-ray diffraction analyses, and clear structural insight into the behavior of an imido functionality on a lanthanide metal center was provided.