| Summary: | This thesis describes new Pd-based catalysts for ethylene polymerization and copolymerization with acrylates. These catalysts feature chelating electronically-asymmetric ligands that contain strong and weak donor groups. In all cases, the strong donor is a phosphine group, and the weak donor is a sulfonate, phosphonate, or phosphinate moiety. In addition to the effects of these different groups on ethylene polymerizations, this thesis also describes the effect of pendant groups and the further modification of these types of catalyst by reactions with different Lewis acids, which results in different ligand coordination modes and the self-assembly of higher structures.
Chapter One introduces Pd-alkyl complexes that contain ancillary phosphine-arenesulfonate ligands. This versatile class of catalyst is one of the few that catalyze the direct copolymerization of ethylene with polar vinyl monomers, and the polar functionalities are incorporated into a highly linear polyethylene backbone. The electronic asymmetry of the phosphine-arenesulfonate ligand is believed to be an important feature of these compounds, resulting in the suppression of [beta]-eliminations that deactivate the catalysts or lead to nonlinear polymer structures. Other important features are believed to be the soft Pd(II) metal center and the multidentate sulfonate group. The performance of these catalysts can be varied by changing the substituents on the phosphine group.
Chapter Two describes a series of benzo-linked phosphine-diethyl phosphonate (P-PO) and phosphine-bis(diethyl phosphonate) (P-(PO)2) ligands and the corresponding (P-PO)PdMe(2,6-lutidine)+ and (P-(PO) 2)PdMe(2,6-lutidine)+ complexes.
Chapter Three describes a multifunctional phosphine-sulfonate-diethyl phosphonate ligand [1-(P(4-tBu-Ph)(2-PO 3Et2-5-Me-Ph))-2-SO3-5-Me-Ph]- ([OP-P-SO]-), which was used to form complexes of type [ κ2-(OP-P-SO)]PdMe(L) (L = 2,6-lutidine, 2b; L = pyridine, 2c).
Chapter Four describes Pd(II)-alkyl complexes of a phosphine-phosphinate ligand (1-PPh2-2-PO2Ph-Ph)-. The complex (κ2-1-PPh2-2-PO2Ph-Ph)PdMe(2,6-lutidine) was prepared and characterized in the solid state. In solution, this compound loses 2,6-lutidine to generate a presumed dimeric species that is only partially soluble in CH2Cl2. The reaction of this mixture with B(C6F5)3 generates soluble borane adduct (κ2-1-PPh2-2-P(O)(O-B(C 6F5)3)Ph-Ph)PdMe(2,6-lutidine).
Chapter Five describes efforts toward multinuclear catalysts supported by aluminophosphonate cages. Several different strategies to assemble these compounds were attempted, which required the synthesis of various phosphine-bis(phosphonic acids), dialkyl arylphosphonates, and unsymmetrical phosphines. The syntheses of simple aluminophosphonate cages {(2-Br-Ph)PO3AlR}4 (R = Me or iBu) and {(2-Br-4-Me)PO3AliBu} 4 is also described. (Abstract shortened by UMI.)
|
|---|
