Structure, bonding, and dynamics of several palladium η3-allyl carbene complexes

A series of Pd-allyl carbene complexes, [PdX(eta(3)-C3H5)(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. C-13, H-1, 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 eta(3)-eta(1) opening of the allyl is under electronic control, and (c) the rates of eta(3)-eta(1) allyl isomerization depend on the X ligand. The solid-state structure of 1c is reported, as well as selected N-15 chemical shift data for the coordinated carbene ligand.