Keeping Track of the Electrons.

Mechanistic investigation and new reaction development are intertwined. This interdependence presents challenges and opportunities in development of all transformations, particularly for those that employ base metal catalysts. In comparison to precious metal counterparts, these catalysts yield less easily to mechanistic analysis. However, base metal catalysts can provide new modes of reactivity and opportunities for discovery. In this Commentary, we highlight a developing field: nickel-catalyzed stereoselective alkyl cross-coupling reactions. While key features of the relevant catalytic cycles remain ambiguous, chemical intuition and key mechanistic experiments have provided the stepping stones for discovery of stereoselective transformations.