Ethylene tetramerization with cationic chromium(I) complexes

Various [Cr(CO)(4)(P boolean AND 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 Cr-I being used as a catalyst precursor for selective tetramerization and gives evidence toward the catalytic cycle acting through a Cr-I -> Cr-III cationic mechanism.