Spectroscopic and Crystallographic Studies on the Insertion Reaction of Aryl Isocyanides into the Bond between Palladium and Carbon, which Contribute to Understanding the trans-[Br2Ni(CNAr)2]-Catalyzed Ethylene Polymerization

The insertion of two sterically different isocyanides into a Pd-Me bond was investigated by spectroscopy and crystallography; this contribute to better understanding of ethylene polymerization catalyzed by trans-[Br2Ni(CNAr)2]. Thus, the reaction of MePdCl(COD) (COD = cyclooctadiene) with a small isocyanide (CNC6H3-2,6-Me2) or a bulky isocyanide (CNC6H3-2,6-Ph2) demonstrated that isocyanide immediately inserted into the Pd-Me bond. Altough the C6H3-2,6-Ph2 group is more bulky than the C6H3-2,6-Me2 moiety, the anisotropic structure of ortho phenyl groups could provide enough space for the insertion by their appropriate rotations. Similarly, the molecular structure of trans-[ClPd{C(Me)=NC6H3-2,6-Ph2}(CNC6H3-2,6-Ph2)2] (5b) provided another example of appropriate rotations of phenyl rings, which ingeniously avoid the inter-ligand repulsions.