Catalytic activity of phenyl substituted cyclopentadienyl neodymium complexes in the ethylene oligomerization process

Abstract

New mono- and bis-cyclopentadienyl neodymium ate-complexes, bearing phenyl-substituents in the cyclopentadienyl ring, have been synthesized: KNdCp′Cl3(thf)x (Cp′ = 1,3-Ph2C5H3 (1), 1,2,4-Ph3C5H2 (2)) and KNdCp′2Cl2(thf)x (Cp′ = 1,3-Ph2C5H3 (3), 1,2,4-Ph3C5H2 (4), 1,2-Me2-4-PhC5H2 (5), 1,2-Ph2-4-(4-MeO-C6H4)C5H2 (6)). Their catalytic activity has been studied in ethylene oligomerization process in the presence of Bu2Mg as a chain transfer reagent with the Nd:Mg molar ratios being of 1:20, 1:40 or 1:80. Complex 4 exhibits catalytic activity close to the activity of the known complex [(C5Me5)2NdCl2Li(OEt2)2] (7). The complex 6 has demonstrated the best catalytic activity among all studied complexes. Using selected complexes 2, 4 and 6 as pre-catalysts, terminal iodo-functionalized oligoethylenes have been prepared. Obtained iodooligoethylenes have been studied by 1H NMR technique and MALDI mass-spectrometry with preliminary derivatization, demonstrating 70–90% of functionalization. Crystal structures of ate-complexes [{(1,2,4-Ph3C5H2)Nd(thf)}2Cl5K]2(toluene)4 (2a), [(1,2,4-Ph3C5H2)2NdCl2K(thf)0.53(1,4-dioxane)1.47]2(dioxane) (4a) and {[{1,2-Ph2-4-(4-MeO-C6H4)C5H2}2NdCl2K]2(1,4-dioxane)}(toluene)4 have been studied by the single crystal X-ray diffraction.