Late and early transition metal-catalyzed homo and copolymerizations studies of olefins and polar monomers

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Stojcevic, Goran
Polymerization , Organometallic
The aims of this work were two-fold. The first part of this thesis involves the synthesis of the Brookhart’s diimine catalyst [Pd(N-N)Me(Et2O)]+ (1) (N-N = (2,6-(i-Pr)2C6H3)-N=CH2CH2=N-(2,6-(i-Pr)2C6H3)) and an investigation of its insertion behaviour with the polar monomer acrylonitrile (AN), as well as its copolymerization behaviour with ethylene. Acrylonitrile displaces the ethyl ether ligand of Brookhart’s cationic complex [Pd(N-N)Me(Et2O)]+ (1) to form the N-bonded species [Pd(N-N)Me(AN)]+ (2) which exists as two equilibrating rotamers (2a and 2b). On heating, [Pd(N-N)Me(AN)]+ which appears to undergo 2,1-insertion, presumably via an unobserved 2 isomer, to give the new complex, [Pd(N-N)(CH(CN)CH2CH3)(AN)]+ (3) which apparently undergoes subsequent -hydrogen elimination to give a hydride which then reacts further with AN to give a cyanoethyl complex (5). Although [Pd(N-N)Me(AN)]+ does behave as a typical Brookhart ethylene polymerization catalyst, it does not catalyze AN polymerization and added AN suppresses ethylene polymerization. [Pd(N-N)Me(AN)]+ does not copolymerize ethylene and acrylonitrile. The second part of this thesis involves utilizing the early metal catalyst rac-Et(Ind)2ZrCl2 (Ind = C9H7) /methylaluminoxane (MAO) to copolymerize propylene or ethylene and the compounds CH2=CH(CH2)7CH2OR {R = Me, (A); PhCH2, (B); Ph3C, (C); Me3Si, (D); Ph3Si, (E)}, all ethers of 9-decen-1-ol. The results showed new copolymer materials of up to 2.0 mol % of incorporated polar monomer into polypropylene and 1.2 mol % for polyethylene. All materials were characterized by 1H and 13C NMR spectroscopy, differential scanning calorimetry and infrared spectroscopy. It was found that the increasing bulkiness of protecting groups did not increase the amount of polar monomer within the copolymers obtained. As a control, propylene-1-hexene copolymerization results were found to be comparable to those results of the polar monomer copolymerization results (up to 2.9 mol % of 1-hexene incorporated). Furthermore, 1H NMR monitoring reactions of the homopolymerization of these vinyl and silyl ethers (A - E) were investigated with the zwitterionic compound G [Cp2ZrMe][MeB(C6F5)3] (Cp = C5H5). It was found that the protecting groups were effective in protecting the functional group from poisoning the catalyst. Finally, the "aging" of MAO by heating, removing trimethylaluminum (TMA) or adding water content all proved to contribute adversely in copolymerization results, whereas adding oxygen content proved to have little effect.
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