Highly Reactive Scandium Phosphinoalkylidene Complex: C–H and H–H Bonds Activation

The
first scandium phosphinoalkylidene complex was synthesized
and structurally characterized. The complex has the shortest Sc–C
bond lengths reported to date (2.089(3) Å). DFT calculations
reveal the presence of a three center π interaction in the complex.
This scandium phosphinoalkylidene complex undergoes intermolecular
C–H bond activation of pyridine, 4-dimethylamino pyridine and
1,3-dimethylpyrazole at room temperature. Furthermore, the complex
rapidly activates H2 under mild conditions. DFT calculations
also demonstrate that the C–H activation of 1,3-dimethylpyrazole
is selective for thermodynamic reasons and the relatively slow reaction
is due to the need of fully breaking the chelating effect of the phosphino
group to undergo the reaction whereas this is not the case for H2.