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Polynuclear magnesium and magnesium-titanium species. Syntheses and crystal structures of [Mg4(μ3η2-ddbfo)2(μ,η2-ddbfo)2(μ,η1-ddbfo)2(η1-ddbfo)2],[Mg4(μ3-OMe)2(μ,η2-ddbfo)2(μ,η1-ddbfo)2(η1-ddbfo)2(CH3OH)5], and [Mg4(μ3,η2-thffo)2(μ,η2-thffo)2(μ,η1-thffo)2{μ-OTi(DIPP)3}2] aggregates.
Autorzy
Rok wydania
2000
Czasopismo
Numer woluminu
39
Strony
235-239
DOI
10.1021/ic990542l
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
Tetranuclear magnesium complexes with chelating alkoxo ligands have been synthesized with the aim of investigating coordinatively unsaturated magnesium sites able to bind TiX4 (X = Cl, OR), of the type necessary for the formation of the active centers in polymerization catalysts. The magnesium compound [Mg4(μ3,η2-ddbfo)2(μ,η2-ddbfo)2(μ,η1-ddbfo)2(η1-ddbfo)2]·2CH2Cl2 (1) (ddbfo = 2,3-dihydro-2,2-dimethyl-7-benzofuranoxide) was prepared by the reaction of MgBu2 with ddbfoH in dichloromethane. Complex 1 exists as a centrosymmetric tetranuclear species with two different types of magnesium centers corresponding to octahedral MgO6 and trigonal bipyramidal MgO5 geometry. Compound 1 is monoclinic, space group P21/c, with a = 12.053(2) Å, b = 13.323(3) Å, c = 17.069(3) Å, β = 98.50(3)o, and Z = 4. The reaction of 1 with methanol in tetrahydrofuran (THF) gave compound [Mg4(μ3-OMe)2(μ,η2-ddbfo)2(μ,η1-ddbfo)2(η1-ddbfo)2(CH3OH)5]·CH3OH·THF (2). During this reaction one of the two five-coordinate MgO5 centers in 1 is completed by a methanol molecule and becomes octahedral in 2. Species 2 belongs to the P21/n monoclinic space group, with a = 13.323(3) Å, b = 20.768(4) Å, c = 27.584(6) Å, β = 104.26(3)°, and Z = 4. Compound [Mg4(μ3,η2-thffo)2(μ,η2-thffo)2(μ,η1-thffo)2{μ-OTi(DIPP)3}2]·2CH2Cl2 (3) is formed as a result of substitution of two thffo (thffo = 2-tetrahydrofurfuroxide) ligands bonded to the five-coordinate magnesium atom in [Mg4(thffo)8] by bulky OTi(DIPP)3 (DIPP = diisopropylphenolate) groups. Crystals of 3 are monoclinic, space group P21/n, with a = 17.069(3) Å, b = 18.421(4) Å, 17.815(4) Å, β = 90.77(3)°, and Z = 4. The X-ray crystal structures of complexes 1−3 are discussed in terms of explaining the role of the coordinatively unsaturated magnesium site in chiral catalyst active center formation.
Słowa kluczowe
Oxygen, Alcohols, Magnesium, Ligands, molecular
Adres publiczny
https://doi.org/10.1021/ic990542l
Strona internetowa wydawcy
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