Synthesis, interionic structure, and reactivity toward CO and p-methylstyrene of palladacyclic compounds bearing a -diimine ligands

Palladacyclic compounds [Pd(C6H4(C6H5C=O)C=N R)(N N)] [X] (R=Et, iPr, 2,6-iPr2C6H3;N N=bpy=2,2’-bipyridine, or 1,4-(o,o’-dialkylaryl)-1,4-diazabuta-1,3-dienes; [X] =[BF4] or [PF6] )were synthesized from the dimers [{Pd(C6H4(C6H5C=O)C=N R)(m-Cl)} 2] and N N ligands. Their interionic structure in CD2Cl2 was determined by means of 19F, 1H-HOESY experiments and compared with that in the solid state derived from X-ray single-crystal studies. [Pd(C6H4(C6H5C=O)C=N R)(N N)] [X] complexes were found to copolymerize CO and p-methylstyrene affording syndiotactic or isotactic copolymers when bpy or 1,4-(o,o’-dimethylaryl)-1,4-diazabuta-1,3-dienes were used, respectively. The reactions with CO and p-methylstyrene of the bpy derivatives were investigated. Two intermediates derived from a single and a double insertion of CO into the Pd C bonds were isolated and completely characterized in solution.