Ethylene Tetramerization with Cationic Chromium(I) Complexes

Various [Cr(CO)4(P∩P)]+ complexes have been synthesized and tested for the tetramerization of ethylene
to give principally 1-octene. The effect of the anion has been investigated, and it has been found that for
successful catalysis an extremely weakly coordinating anion is required. This study shows that when
[Al(OC(CF3)3)4]- is employed as the anion, along with triethylaluminum and PNPiPr as the coordinated
diphosphine, the system is active for the tetramerization of ethylene. This is the first example of CrI
being used as a catalyst precursor for selective tetramerization and gives evidence toward the catalytic
cycle acting through a CrI → CrIII cationic mechanism.