UC Santa Barbara

In attempts to develop tandem catalysis of alkane dehydrogenation and polyol deoxydehydration, the reactivity of a (tBuPCP)IrH2/H4 (PCP=[κ3-2,6-C6H3(CH2PtBu2)2]) and methyltrioxorhenium was explored. The resulting bimetallic complex, [(tBuPCP)Ir(ReO3)(H)], which was stable at low-temperature, quickly turned into [(tBuPCP)Ir(ReO4)(H)] at room temperature. The reactivity of these highly oxophillic bimetallic complexes was studied. With NMR and DFT studies, the pathway of bimetallic formation was elucidated.

Ethylene/1-hexene copolymerization by a single-site hafnium salan-type catalyst activated by B(C6F5)3 produced high 1-hexene-incorporated copolymers. The composition dependence on monomer concentrations and reaction time was explored. Deuterium labeling experiments revealed that primary sites decreased as secondary sites increased over the course of the reaction. The secondary sites showed no reactivity towards the polymerization of ethylene and 1-hexene. High 1-hexene concentration suppressed catalyst deactivation. In-situ NMR demonstrated a positive comonomer effect, where higher kobs of ethylene and 1-hexene were achieved with increased [1-hexene]0.

New methods (in-situ NMR with high-pressure NMR cell and batch reactor with Auto-Sampler) for quantitative kinetic study of selective ethylene tri/tetra-merization by chromium N-phosphinoamidine were developed. The monomer consumption and 1-hexene versus 1-octene product formation in real-time was reported for various catalysts.