The anilide-methyl complex (PNP)ScNH[DIPP](CH3) (1 ) (PNP = bis(2-diisopropylphosphino-4-tolyl)amide, DIPP = 2,6-diisopropylphenyl), eliminates methane at room temperature in the presence of pyridine to generate the transient scandium imido, (PNP)Sc=N[DIPP](NC5H5) (A -py), which rapidly activates the C-H bond of pyridine in 1,2-addition fashion to form the stable pyridyl complex (PNP)Sc(NH[DIPP])(h2-NC5H4) (2 ). Kinetic and mechanistic studies suggest the C-H activation process to be second-order overall. Pyridine binding precedes elimination of methane and a-hydrogen abstraction and is overall rate-determining.  Substituted pyridines can also be activated. DMAP and 4-picoline accelerate the a-hydrogen abstraction process in 1 , while hindered bases such a 2-picoline, 2,6-lutidine or other 2-substituted pyridines inhibit this step. C-H bond activation products have been fully characterized, and in the case of 2-picoline, activation of the aromatic and aliphatic group results in an equalmolar mixture of regioisomers, both of which have been structurally characterized.

Evidence for the existence of terminal scandium imidos: Mechanistic studies involving imido-scandium bond formation and C−H activation reactions

245th National Meeting (2013)

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