Synthesis of N , N ′, X ‐tridentate 2‐iminomethylpyrrole‐coordinated palladium(II) complexes via N─H bond activation of pyrrole moiety

The reaction of [Pd(CH 3 CN) 2 Cl 2 ] with N ‐functional group‐substituted 2‐iminomethylpyrrole‐based ligands, namely N 1 ‐((1H‐pyrrol‐2‐yl)methylene)‐ N 3 , N 3 ‐dimethylpropane‐1,3‐diamine (L A ), N 1 ‐((1H‐pyrrol‐2‐yl)methylene)‐ N 3 ‐methyl‐ N 3 ‐phenylpropane‐1,3‐diamine (L B ), N ‐((1H‐pyrrol‐2‐yl)methylene)‐3‐(methylthio)propan‐1‐amine (L C ) and N ‐((1H‐pyrrol‐2‐yl)methylene)‐3‐methoxypropan‐1‐amine (L D ), resulted in [L n PdCl] (L n  = L A –L D ) complexes in high yield via N─H bond activation of pyrrole moiety without use of base. [L n PdCl] existed as monomeric four‐coordinated complexes with slightly distorted square planar geometries around the palladium metal center. The ligands show N , N ′, X ‐tridentate binding mode to the palladium metal center to give two fused ring metallacycles. [L B PdCl] gave the highest activity (3.29 × 10 5  g PMMA (mol Pd) −1  h −1 ) for a methyl methacrylate (MMA) polymerization in the presence of modified methylaluminoxane at 60 °C compared to the other Pd(II) analogues, and resulted in PMMA with higher molecular weight ( M w  = 7.16 × 10 5  g mol −1 ) and narrower polydispersity index. Syndiotactic‐enriched PMMA resulted in all cases.