Structure and Reactivity of Palladium Complexes Bearing Asymmetric Anilido-Imine Bidentate Ligands

With recent versatile applications in bioinorganic, main group, and transition metal chemistry, the research in β-diketiminato ligands of N-N bidentates and the salicylaldiminato ligands of N-O bidentates has been rising dramatically.
We have successfully synthesized a series of ligands with functional combination of anilido-imine (o-C6H3R'2)NHC6H4CH=N(o-C6H3R2) ( 2a R' = iPr, R = iPr; 2b R' = CH3, R = iPr; 2c R' = iPr, R = CH3; 2d R' = CH3, R = CH3, 2e R' = CH3, R = H) and their related anionic form LiN(o-C6H3R'2)C6H4CH=N(o-C6H3R2) (L3) ( 3a R' = iPr, R = iPr; 3b R' = CH3, R = iPr; 3c R' = iPr, R = CH3; 3d R' = CH3, R = CH3) via deprotonation. The photoluminscence nature of complexes 3 corresponding to their structures has been studied. These coordination of derivates (3) can generate a square-planar complex (L)Pd(CH3)(PPh3)(4) by reacting with (COD)Pd(Me)Cl and PPh3. NMR measurements show that the methyl ligand is trans to the imine. The reactions of L3 with [(η3-C3H4R")PdCl]2 afford two geometric isomers of η3-allyl species which have been well characterized by sophisticated 2D-NMR. The steric and electronic effects of the anilido-imine ligands can influence the regioselectivity as well as the ratio of isomers.
The palladium complexes (4) are active to the Heck and Suzuki cross-coupling reactions, and its TON can reach to 103~104. These catalysts (4) also show activity about 105gPNmol-1h-1 to the polymerization of norborene.