Hydrogen Bonding Behavior of Amide-Functionalized α-Diimine Palladium Complexes

A class of (N,N′-diaryl-α-diimine)Pd complexes bearing amide substituents on the N-aryl rings is described. Hydrogen bonding interactions involving the amide groups influence the structures, isomer distributions, and ligand coordination behavior of these compounds. The amide-functionalized α-diimine ligands (2,6-iPr2-Ph)N═CMeCMe═N(2-C(═O)NMe2-6-iPr-Ph) (4a), (2,6-iPr2-Ph)N═CMeCMe═N(2,6-(C(═O)NMe2)2-Ph) (4b), and (2-C(═O)NMe2-6-iPr-Ph)N═CMeCMe═N(2-C(═O)NMe2-6-iPr-Ph) (4c) were prepared by condensation reactions of 2,3-butanedione and the appropriate anilines. The attempted preparation of (2,6-iPr2-Ph)N═CMeCMe═N(2-C(═O)NHMe-6-iPr-Ph) (4d) yielded the corresponding 1,2-dihydroquinazolinone derivative 4d′ formed by nucleophilic attack of the amide nitrogen at the proximal imine carbon. 4a and 4b react with (cod)PdMeCl to yield square planar (α-diimine)PdMeCl complexes 5a,a′ and 5b,b′, respectively, which exist as two isomers that differ in the orientation (trans/cis) of the Pd–Me ligand and the amide-substitu...