The mechanism of controlled radical polymerization of vinyl acetate using vanadium catalysts is investigated using a range of experimental and computational studies. Optimal control is achieved using the non-innocent bis(imino)pyridine ligand framework. [BIMPY]VCl 3 , where BIMPY = 2,6-[(2,6i Pr 2 C 6 H 3)N=C(Me)] 2 (C 5 H 3 N)), is one of only a few transition metal systems capable of mediating the polymerization of vinyl acetate. Initiation using AIBN at 120°C results in excellent control over poly(vinyl acetate) molecular weights and PDIs, to give vanadium-terminated polymer chains which can be readily converted to both proton-terminated poly(vinyl acetate) or poly(vinyl alcohol). Irreversible halogen transfer from the parent [BIMPY]VCl 3 complex to a radical derived from AIBN generates the active species, [BIMPY]VCl 2. This catalyst cannot use the halogen atom transfer equilibrium to control polymerization, but can act as a persistent radical and trap the propagating polymer chains through an OMRP reversible termination process. Computational studies support this novel two-step reaction pathway and reveal that the poor control exerted over styrene versus the excellent control observed for vinyl acetate under these conditions is not only dependent on radical reactivity, but also due to chelation of the carbonyl group of vinyl acetate to the vanadium center, making the trapping step more favorable. This correlates with an energy difference of just 4 kcal/mol between the reduced [BIMPY]VCl 2 , and [BIMPY]VCl 2 R species for vinyl acetate compared to over 20 kcal/mol for styrene. This [BIMPY]VCl 3 system can be extended to other vinyl ester monomers, with good control over molecular weights and PDIs obtained for vinyl propionate, vinyl pivalate and vinyl benzoate.

Initiation of the polymerization of vinyl acetate with azobis(isobutyronitrile) in the presence of a vanadium bis(iminopyridine) complex generates vanadium-capped dormant polymer chains with excellent correlation between molecular weight and conversion and good molecular weight distributions.

A range of sterically hindered diimine ligands and their palladium (II) complexes were synthesized. These compounds were fully characterized by elemental analysis, 1 H and 13 C-NMR spectroscopy. The use of the palladium complexes as catalysts for Suzuki and Heck coupling has been studied in an attempt to demonstrate the effect of side groups on catalytic activity. It was clearly seen that the location of side -CH 3 groups which bound to benzene ring had little effect on catalytic activity. Interestingly when we changed these -CH 3 groups with -Cl groups the activity of the complexes increased. On the other hand, side groups which bound to imine nitrogen also had a large effect on catalytic activity.

Water-soluble Mo(0) tetracarbonyl complexes containing a a-diimine ligand have been prepared. All the complexes were characterized by elemental, LC-MS (APCI), FT-IR, 1 H-NMR, and 13 C-NMR spectroscopy. The pH dependent phase transfer of these complexes was investigated. This pH dependent phase transfer was accomplished over 10 times with no evidence of complex decomposition. Their catalytic activities on methyl methacrylate polymerization were determined.

No abstract