Structure, Bonding, and Dynamics of Several Palladium eta3-Allyl Carbene Complexes

A series of Pd-allyl carbene complexes, [PdX(η3-C 3H5)(IPr)], 1 (X = a, Cl- , b, Br- , c, I- , d, N3-, e, NCO-, f, SCN-, g, CN-, h, OAc-, i, OTf-, j, 4-Me-pyridine), have been studied by one- and two-dimensional NMR techniques. 13C, 1H, and phase-sensitive NOE NMR studies on these relatively simple complexes reveal that (a) the trans influence of the carbene carbon in 1 seems to be smaller than that found for PPh3 and other P-donor ligands, (b) the selective η3-η1 opening of the allyl is under electronic control, and (c) the rates of η3-η1 allyl isomerization depend on the X ligand. The solid-state structure of 1c is reported, as well as selected 15N chemical shift data for the coordinated carbene ligand.