β-Diketiminato Scandium Chemistry: Attempted Deprotonation of Cationic Amido Complexes

Treatment of the β-diketiminato-supported scandium
amido methyl derivatives [ArNC(tBu)CHC(tBu)NAr]Sc(Me)(NHR) (Ar = 2,6-iPr2-C6H3; R = tBu, 2,6-iPr2-C6H3) with 1
equiv of tris(pentafluorophenyl)borane resulted in the formation
of scandium amido ion pairs, 1a and 1b, respectively, in good
yields. A single-crystal X-ray analysis of 1a was undertaken,
and two crystallographically independent molecules were
observed in which one contains an N−H···F−C hydrogen bond
while the other does not. Several attempts to deprotonate the
amido ligand to yield a neutral imido species resulted in either
attack of the base at the metal center or deprotonation of the
β-diketiminato ligand. For example, treatment of 1a with tert-butyllithium gave [ArNC(tBu)CHC(tBu)NAr]Sc(CMe3)(NHtBu)
(2), while treatment with the phosphazene base [(Me2N)3PN]3PNtBu gave the previously characterized metalated
complex 3.