Palladium(II) complexes bearing ethylene-bridged S∩As and S∩P donor ligands: synthesis, crystal structure and reactivity towards the polymerization of norbornene

Abstract

Palladium(II) complexes of the general type [Pd(L∩L)Cl 2] ( 4– 6) and their corresponding dicationic complexes [Pd(L∩L)(NCCH 3) 2](BF 4) 2 ( 7– 9) (L∩L=[(1-(thiomethyl)-2-(diphenylarsino)ethane] (S∩As, 1) ( 4, 7) [1-(thiomethyl)-2-(diphenylphosphino)ethane] (S∩P, 2) ( 5, 8) and [1,2-bis(diphenylphosphino)ethane] (P∩P, 3) ( 6, 9) have been synthesized and utilized as catalysts for the polymerization reaction of bicyclo[2.2.1]hept-2-ene (norbornene). The dichloride complexes can be activated with methylaluminoxane (MAO), while the corresponding dicationic compounds were used as single component catalysts for the polymerization reactions. Catalytic performance of the new type of catalyst can be altered by modifying the donor atoms in the bidentate ligand. The activity of the Pd(II) complexes towards the polymerization reaction increases with increasing the trans-influence of the donor atoms (P∩P>S∩P>S∩As). The influence of donor atoms on the length of the PdCl bonds was elucidated by X-ray structure analysis carried out on the palladium(II) complex [Pd(S∩As)Cl 2] ( 4).