Synthesis and reactivity of sterically hindered iminopyrrolato complexes of zirconium, iron, cobalt and nickel

David M. Dawson, Dennis A. Walker, Mark Thornton-Pett, Manfred Bochmann

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The new bis(imino)pyrrole ligand 2,5-C4H2NH(CH==NC6H3Pri2)2 (HL1) reacts with Zr(NMe2)4 to give the 1:1 complex (L1)Zr(NMe2)3 (1), whereas the mono(imino)pyrrole 2-C4H3NH(CH==NC6H3Pri2) (HL2) substitutes two amido ligands to give (L2)2Zr(NMe2)2 (2). The lithium salt LiL1 reacts with ZrCl4 to give (L1)ZrCl2(µ-Cl)2Li(OEt2)2 (3), while the reaction of LiL2 with ZrCl4 or treating 2 with Me3SiCl gives (L2)2ZrCl2. Iron(II) chloride reacts with LiL1 to afford the bis(ligand) complex Fe(L1)2 (5), while only one pyrrolato ligand is incorporated on reacting LiL1 with CoCl2(thf) to give [Li(thf)4][CoCl2L1] (6a). On warming, 6a readily loses thf to give [Li(thf)2][CoCl2L1] (6b). By contrast, LiL2 reacts with CoCl2 and NiCl2 to give the halide-free complexes Co(L2)2 and Ni(L2)2, respectively. The crystal structures of HL1 and complexes 1, 2 and 5 are reported. In all cases the potentially tridentate ligand L1 is two-coordinate. Mixtures of the halide-free bis(ligand) complexes with methylaluminoxane do not show any activity for ethene polymerisation; however, 3 and 4 catalyse the polymerisation of ethene, while 6 has moderate activity for the oligomerisation of ethene and propene to linear and branched products.
Original languageEnglish
Pages (from-to)459-466
Number of pages8
JournalJournal of the Chemical Society, Dalton Transactions
Issue number4
Publication statusPublished - 2000

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