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).