NHO to aNHC Isomerization at a Pd 0 ‐Center

N‐heterocyclic carbenes (NHCs) are a highly important class of ligands in transition metal‐mediated catalysis. Recently, a modification of the NHCs has received considerable interest, the N‐heterocyclic olefins (NHOs) with an exocyclic methylene appended to the NHC. In here we investigated the propensity of NHOs to act as a ligands for Pd 0 complexes derived from [Pd 2 (dvds) 3 ]. The reaction of IPrCH 2 and IMesCH 2 with the Pd 0 precursor [Pd 2 (dvds) 3 ] resulted in the formation of abnormal N‐heterocyclic carbene complexes [(aIPrCH 3 )Pd(dvds)] ( 1 ) and [(aIMesCH 3 )Pd(dvds)] ( 2 ). DFT calculations were applied to study this isomerization and to reveal the bonding in 1 and 2 . In addition, the backbone‐methylated NHOs Me IPrCH 2 and mMe IMesCH 2 ( 4 ) were shown not to undergo the isomerization observed in IPrCH 2 and IMesCH 2 .