Synthesis and Reactivity of a Terminal Scandium Imido Complex

Preparation of a terminal scandium imido complex, 2·DMAP, was accomplished through thermolysis of an arylamido
methyl complex, 1, stabilized by a bulky β-diketiminato
ligand in the presence of 4-N,N-dimethylaminopyridine
(DMAP). Mechanistic studies revealed that the reaction proceeds by
initial metalation of 1, followed by rapid DMAP-promoted
alkane elimination to generate the scandium imido complex. Kinetic
studies of the reaction between separately synthesized metalate 3 and DMAP under pseudo-first-order conditions yielded activation
parameters of ΔH⧧ = 73.5(2) kJ mol–1 and ΔS⧧ = −70.4(5) J K–1 mol–1. The reaction of 2·DMAP
with tert-butyl amine or phenylacetylene resulted
in addition of the N–H or C–H bond across the scandium
imide linkage, respectively, to furnish complexes endo-/exo-4 and endo-5. These compounds were fully characterized, including via
structural analysis, providing further evidence for the terminal scandium
imido derivative 2·DMAP.