Design of new multidendate PCN ligands to improve Philips catalyst system in selective oligomerization of ethylene

To the development of systems for selective tri/tetramerization of ethylene to 1- hexene and 1- octene in ethylene oligomerization, various changes on Philips catalyst systems as pioneer industrial method have been done by design of organophophorous systems. Different type of multidentate ligands with N, P, C and S donors are capable to stabilize chromium cycle in catalyst process [1]. The ability of 1- phosphanyl methanimine type ligand in improving selectivity and activity of catalyst for prodution high yield of 1- hexene and 1- octene have been investigated and get considerable attention by researcher [2-3]. In this work PCN ligands are designed by nucleophilic substitution of trivalent phosphorous in trimethylsilylphosphines with chloride in electrophilic iminium carbon bond (-Cl-C=N-) to form desire C-P bond. Different aliphatic and aromatic phosphines were selected to investigate the electronic and steric effect of phosphine functional groups on catalyst behavior. The appropriate trimethylsilyl phosphines are synthesized with deals of phosphines with trimethylsilyl chloride in the present of alkaline metals. Subsequently the reaction of imidoyl chloride with trimethylsilyl phosphine gives L1 and L2. General synthetic route for preparation of trimethylsilylphosphines and ligands L1 and L1 are shown in Scheme 1.