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 [A1(OC(CF 3) 3) 4] - is employed as the anion, along with triethylaluminum and PNP iPr as the coordinated diphosphine, the system is active for the tetramerization of ethylene. This is the first example of Cr I being used as a catalyst precursor for selective tetramerization and gives evidence toward the catalytic cycle acting through a Cr I → Cr II cationic mechanism. © 2007 American Chemical Society.