Revealing the electron driven mechanism in metal catalyzed Kumada cross coupling reaction

The electron motion mechanism of the metal-catalyzed Kumada cross-coupling reaction, which synthesizes biphenyl from chlorobenzene and phenylmagnesium chloride (a Grignard reagent) using a palladium (Pd) complex with an auxiliary phosphine ligand, is elucidated. This analysis is grounded in reactive orbital energy theory (ROET), enabling the examination of electron motions in comprehensive chemical reactions. We first calculated the intrinsic reaction coordinates (IRCs) for the four key processes of this reaction: oxidative addition, transmetalation steps 1 and 2, and reductive elimination. Using automatic orbital tracing in the ROET analysis, we identified the reactive orbitals for these IRCs. Consequently, we revealed the sequential electron motions driving these processes through animations, clarifying the electronic roles of the Pd center, the auxiliary ligand, and the Grignard reagent. These electron motions are consistent with experimental observations, indicating that the electron motions driving metal complex reactions can be effectively represented by changes in a single molecular orbital.