Off-campus UMass Amherst users: To download dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.
Non-UMass Amherst users, please click the view more button below to purchase a copy of this dissertation from Proquest.
(Some titles may also be available free of charge in our Open Access Dissertation Collection, so please check there first.)
New group 4 organometallic complexes and their use as homogeneous alpha-olefin polymerizatin catalysts
Abstract
Eight new half-sandwich titanium catalyst precursors were prepared, and their catalysis of syndiospecific styrene polymerization when activated by methylaluminoxane was studied. Phenyl substitution increases polymerization activity in the order 15 $<$ 13 $<$ 11; the opposite trend was observed for the yield of syndiotactic polystyrene (s-PS). Benz (e) IndTiCl$\sb3$ (17) as well as the 2-methyl (19) and 1,2,3-trimethyl (23) derivatives were synthesized. Catalysts 17/MAO and 19/MAO exhibit exceedingly high activity, and produce s-PS with high stereoregularity and molecular weight. A variety of methoxy and phenyl-substituted (indenyl)titanium trichloride complexes were synthesized, and these precursors were used to polymerize styrene, ethylene, and propylene. The complexes, when activated with MAO, show only low activity for the polymerization of styrene and ethylene and no activity for propylene polymerization. Oxygen-aluminum coordination between the methoxy group and MAO could be one of the deactivating interactions. 9- ((2-t-Butylamino)ethyl) fluorene (66) was synthesized by the use of (1-chloro-2-t-butylamino)ethane (65) which provided convenient routes to 66 as well as 3- ((2-t-butylamino)ethyl) indene (67). Deprotonation of 66 with 2 equivalents of butyllithium followed by addition of ZrCl$\sb4$ or HfCl$\sb4$ led to (1-($\eta\sp1$-t-butylamido)-2-($\eta\sp5$-9-fluorenyl)ethane) zirconium (68) and hafnium (69) dichloride, respectively. Complexes 68 and 69 when activated with methylaluminoxane (MAO) are active catalysts for the polymerization of ethylene. A variety of new unbridged metallocene complexes were synthesized. Bis($\eta\sp5$-2-methylbenz (e) indenyl)zirconium dichloride (80) was activated with both MAO and triphenylcarbenium tetrakis(pentafluorophenyl)borate (trityl)/triisobutylaluminum (TIBA) producing polypropylene with varying molecular weight depending on polymerization temperature. The precursor ($\eta\sp5$-4,5,6,7-tetrahydro-1,2-dimethylbenz (e) indenyl)zirconium dichloride (101) when activated with trityl/TIBA produced a mixture of atactic and isotactic polypropylene (i-PP) with 51% mmmm pentads. The silicon bridged ansa-metallocene (dimethylsilanediylbis($\eta\sp5$-1,1$\sp \prime$-(4,5,6,7-tetrahydro-2-methylbenz (e) indenyl))) zirconium dichloride (105) was activated with MAO to produce i-PP with an activity of $1.0\times10\sp8$ g of PP/(mol of Zr$\rm\cdot\lbrack C\sb3H\sb6\rbrack{\cdot}h)$ and higher isotacticity than that produced by the unbridged analog (100). A new polycyclic ligand, 2-methylbenz (f) indene (111), was synthesized. Attempts to convert 111 into Group 4 organometallic complexes failed, however a rhodium dicarbonyl complex 112 was synthesized. The unsuccessful synthesis of Group 4 complexes was attributed to the loss of resonance stabilization in the proposed pentahapto coordinated complexes.
Subject Area
Polymers|Organic chemistry|Chemistry
Recommended Citation
Foster, Patrick, "New group 4 organometallic complexes and their use as homogeneous alpha-olefin polymerizatin catalysts" (1997). Doctoral Dissertations Available from Proquest. AAI9737526.
https://scholarworks.umass.edu/dissertations/AAI9737526