Neutral nickel and palladium complexes as catalysts in copolymerizations of polar and non-polar monomers

Abstract

The thesis deals with Pd(II) catalysts, bearing anionic phosphine/ sulfonate ligands (PSO), with the intention of making non-alternating E/ CO-copolymers accessible. Starting from the Pd precursor [(dcp)PdCl]2, SCCs (single component catalyst), with a variable substitution pattern in the phosphine moiety and their influence on the polymeric products are described. The structures of the dimeric complexes and (PSO)Pd(dcp) catalysts are proved. Experiments clearly show, that according to DFT calculations, the ligand, bearing the bulkiest substituent in ortho-position (-isopropoxy) yielded the highest amount of extra-ethylene in the copolymer. The highest amount (36 % on top) was obtained, when CO was added at a slave factor of 5. The same PSO catalysts also show the ability of copolymerizing C2H4 and acrylates. In chapter 3, nickel complexes of the PSO ligands were tested as C2H4 polymerization catalysts. (PSO)Ni(Ph)(PPh3) complexes are synthesized, which gave a highly active system for ethylene polymerizations. Without applying any scavengers, the catalyst produced reasonable amounts of polymer. By increasing the sterical bulk of the ligand (-isopropoxy) and the electronic influence on the metal ion, the equilibrium of coordinated and free triphenylphosphine is shifted to the latter, causing a significant raise in the activity. In chapter 4 a deprotonated phosphonic acid group is supposed to coordinate to the metal center. Thus, phosphine/ phosphonate and phosphine/ phosphinate ligands with a variety of substitution patterns are synthesized. X-ray analysis of the complexes revealed a chelated coordination mode of the PPO ligands to be true. The complexes developed in this chapter do up to now not show any catalytical activity in preliminary polymerization experiments. However, it is proved in this chapter, that these ligands do not only coordinate via their phosphorus atom as stated in the literature before, but act as chelating ligands.