Two approaches to selective oligomerization of light alkenes

There is currently much interest in developing methodol. for upgrading light (C_(2-5)) hydrocarbons to more valuable fuels. Schemes based on alkene oligomerization are attractive, but accomplishing that selectively is a challenging requirement. We have been studying two very different systems: an air- and water-stable hydroxy-bridged dimeric Pd(II) complex that selfactivates to generate an oligomerization catalyst; and bis(phosphine)Cr(III) complexes that catalyze selective ethylene trimerization upon activation with MAO. I will discuss recent mechanistic findings and their implications for potential applicability to desirable conversion processes.