C–H Bond Activations by Monoanionic, PNP-Supported Scandium Dialkyl Complexes

A series
of scandium dialkyl complexes, (PNP)­ScR2 (R
= neopentyl, trimethylsilylmethyl), supported by the monoanionic,
chelating PNP ligand (2,5-bis­(dialkylphosphinomethyl)­pyrrolide; alkyl
= cyclohexyl, tert-butyl) was synthesized, and the
reactivities of these complexes toward simple hydrocarbons was investigated.
The scandium–carbon bonds undergo σ-bond metathesis reactions
with hydrogen, and these complexes are catalysts for the hydrogenation
of alkenes. Reactions with primary amines led to formation of amido
complexes that undergo cyclometalation via σ-bond metathesis,
without involvement of an imido complex intermediate. A variety of
carbon–hydrogen bonds are also activated, including sp-, sp2-, and sp3-C–H bonds (intramolecularly in
the latter case).