Synthesis and structural characterization of magnesium and titanium siloxanes

Dimeric magnesium complex with siloxane OSiPh3 ligands have been synthesised with the aim of investigating magnesium sites able to bind TiX4 (X=Cl, OR), of the type necessary for the formation of the active centres in polymerisation catalysts. The magnesium compound [Mg2(μ-OSiPh3)2(OSiPh3)2(THF)2] (1, 76%) was prepared by reaction of [Mg4(thffo)8] (thffo-H=tetrahydrofurfuryl alcohol) with Ph3SiOH in tetrahydrofurane (THF). The addition of TiCl4 to 1 in a 2:1 molar ratio results in the formation of [TiCl2(OSiPh3)2(THF)2]·2THF (2, 50.5%). The reaction of 1 with 4 equiv. of cis-[TiCl2(η2-maltolato)2] (maltolato=(O,O)-3-oxy-2-methyl-pyran-4-onato) in CH2Cl2 gave compound [TiCl(OSiPh3)(η2-maltolato)2]·THF (3, 72%). Straightforward chloride replacement reaction in 3 by use of LitBu and Ph3SiOH results in the formation of species [Ti(tBu)(OSiPh3)(η2-maltolato)2] (4, 63%) and [Ti(OSiPh3)2(η2-maltolato)2] (5, 91%), respectively. The molecular structures of compounds 2 and 3 have been determined by X-ray structure analysis.