Chromium(III) catalysed ethylene tetramerization promoted by bis(phosphino)amines with an N-functionalized pendant.

Several N-functionalized bis(phosphino)amine ligands with ether, thioether and pyridyl tethers [(R'')2PN(R')P(R'')2=PNP] () have been synthesized. They react with CrCl3(THF)3 in CH2Cl2 to give dinuclear chloro bridged Cr2(micro-Cl)2Cl4(PNP)2 () which converts to the corresponding mononuclear solvento complexes fac-CrCl3(PNP)(NCR) (). The structures of the ligand with R'=-(CH2)3SCH3 and R''=Ph, and the complexes with R=CH3 () and C2H5 (), R'=-(CH2)3SCH3 and R''=Ph) have been established by single-crystal X-ray crystallography. All ligands are active towards ethylene tetramerization in the presence of Cr(III) and excess MAO at 80 degrees C in toluene. The ligand with thioether pendant Et2PN(CH2CH2CH2SCH3)PEt2 () shows the highest selectivity (55% weight in liquid product distribution) towards 1-octene. Complexes and are active towards ethylene polymerization under thermal conditions.