Structural characterization of manganese(II) compounds with methylalumoxane (MAO) and AlMe2 units

Manganese complexes with AlMe3 have been synthesized with the aim of investigating Mn(II) active centers in catalytic ethylene polymerization. Reactions of [Mn-4(mu-Cl)Cl-3(mu-OCH2CH2OCH3)(4)(HOCH2CH2OCH3)(3)](2) (1) with an excess of AlMe3 at room temperature in toluene give the heterometallic cage [Mn3Al(mu(3)-OCH2CH2OCH3)(mu-Cl)(3)(mu-OCH2CH2OCH3)(2)(thf)(2)(Me)(2)Cl] (2; 30%). A similar reaction carried out under reflux led to the formation of the methylalumoxane species [MnAl3(mu(3)-O)(A-OCH2CH2OCH3)(3)(Me)(6)] (3; 51%). X-ray diffraction studies have shown complexes 2 and 3 to contain AlMe2+ and [Al-3(mu(3)-O)(Me)(6)](+) moieties capped by [Mn-3(mu(3)-OCH2CH2OCH3)(mu-Cl)(3)(mu-OCH2CH2OCH3)(2)(thf)(2)Cl](-) and [Mn(mu-OCH2CH2OCH3)(3)](-) macrounits, respectively. The tendency of a manganese center to exchange aluminum methyl groups in 2 and 3 is strongly reduced by alkoxide ligands.