The oxidative addition of benzene derivatives to Pd catalysts is a key step in cross-coupling reactions. In this work, we show that the ipso-carbon chemical shift of substituted benzenes, and in particular the δ component of the chemical shift tensor, correlates with the free energy barrier for oxidative addition. This correlation is traced back to the electron density in the p orbital of the ipso-carbon (perpendicular of the ring-plane), with high electron densities favoring oxidative addition. The correlation between chemical shift and free energy barrier holds true for a variety of substituted benzenes, making chemical shift a useful descriptor for predicting the reactivity of aromatic substrates in oxidative addition.
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