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

The
scandium bis­(alkyl) complex bearing the phosphazene ligand
L1Sc­(CH2SiMe3)2 (1) (L1 = N­(PPh2NPh)2) reacted with an equimolar amount of 2,6-diisopropylaniline to afford
the corresponding mixed alkyl/anilido complex L1Sc­[NHC6H3(iPr)2]­(CH2SiMe3) (2). Under mild conditions
(20 °C, 4 h or 0 °C, 12 h), complex 2 could
be swiftly transformed to the terminal imido complex L1ScN­[C6H3(iPr)2]­(DMAP)2 (4) in the presence
of DMAP (DMAP = 4-N,N-dimethylaminopyridine). Correspondingly,
treatment of the yttrium and lutetium bis­(alkyl) complexes L2Ln­(CH2SiMe3)2 (L2 = N­[Ph2PNC6H3(iPr)2]2; Ln = Y (7), Lu (8)) with equimolar amounts of 2,6-diisopropylaniline gave
the mixed alkyl/anilido complexes L2Ln­[NHC6H3(iPr)2]­(CH2SiMe3) (Ln = Y (9), Lu (10)),
which, however, underwent dealkylation of the Ln–CH2SiMe3 species at temperatures of 60 °C for 9 and 100 °C for 10 to afford bis­(anilido)
complexes L2Ln­[NHC6H3(iPr)2]2 (Ln = Y (11), Lu (12)) as redistribution products. All these complexes
have been characterized by 1H, 13C­{1H}, and 31P­{1H} 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.