Synthesis and structures of ferrocenyl-substituted salicylaldiminato complexes of magnesium, titanium and zirconium

N-ferrocenyl salicylaldimine (FcPI)H, readily accessible from aminoferrocene and salicylaldehyde, reacts with dibutylmagnesium in THF to afford a red crystalline (FcPI)2Mg(THF)2 (2). The reactions of the Li(FcPI) with CpTiCl3 gave CpTiCl2(FcPI) · CH2Cl2 (4), whereas with CpZrCl3 · DME a mixture of three products is formed: CpZrCl(FcPI)2 (5), CpZrCl2(FcPI) (6), and (FcPI)2ZrCl2 · CH2Cl2 (3 · CH2Cl2). The crystal structures of compounds 2–6 are reported. Typically, the N–O chelates are oriented such that O donors are mutually trans, while N donors prefer to be trans to Cl ligands. The redox potentials of these complexes are very similar to ferrocene. On activation with methylaluminoxane, the Ti complex 4 shows moderate activity for ethylene polymerisation, while (FcPI)2ZrCl2 is highly active for the oligomerisation of ethylene, to give products with average degrees of polymerisation of 12–16.

Graphical abstractThe preparation and structures of the N-ferrocenyl salicylaldiminato complexes (FcPI)2Mg(THF)2, CpTiCl2(FcPI) · CH2Cl2, CpZrCl(FcPI)2, CpZrCl2(FcPI), and (FcPI)2ZrCl2 · CH2Cl2 is described. They are electrochemically active, with redox potentials close to ferrocene. On activation with methylaluminoxane, the Ti complex polymerises ethylene, while (FcPI)2ZrCl2 is a highly active ethylene oligomerisation catalyst.Figure optionsDownload full-size imageDownload as PowerPoint slide