Synthesis of diphenylphosphinoamine Ligands and their catalytic performance for ethylene tetramerization with Cr(III) compounds

Diphenylphosphinoamine ligands were synthesized by reacting bis(phenyl) phosphorus chloride with diamines. They exhibited exceptionally high selectivity (up to 73.1%) towards 1-octene and catalytic activity for ethylene tetramerization in the presence of Cr(III) compounds (chromium chloride tetrahydrofuran or chromium acetyl acetonate) and methylaluminoxane. Besides the target product 1-octene, main side-products such as 1-hexene, methylcyclopentane, and methylenecyclopentane are also valuable. The activity and the selectivity for 1-octene are dependent on the catalyst ligand structure and the reaction conditions such as reaction temperature, pressure, and the Al/Cr molar ratio, while the Cr(III) compounds have nearly no effect on them.