title: A structurally diverse series of aluminum chloride alkoxides [Cl(x)Al(mu-OR)(y)](n) (R = (n)Bu, (c)Hex, Ph, 2,4-(t)Bu2C6H3).
abstract: A diverse series of aluminum chloride alkoxides, [Cl(x)Al(mu-OR)(y)](n) (R = (n)Bu, (c)Hex, Ph, 2,4-(t)Bu(2)C(6)H(3)), was synthesized using the reactions of dichlorethylalane (EtAlCl(2)) with cyclohexanol ((c)HexOH), n-butanol ((n)BuOH), and phenols (PhOH and 2,4-(t)Bu(2)C(6)H(3)OH). Eight molecular products were isolated and structurally characterized. The dimeric [Cl(2)Al(mu-O(c)Hex)(2)AlCl(2)] (1) was the smallest oligomer isolated among the cyclohexanolate derivatives. The adduct of 1 with cyclohexanol is a dinuclear molecule [Cl(2)(HO(c)Hex)Al(mu-O(c)Hex)(2)AlCl(2)] (2) which represents a possible intermediate in the conversion reaction leading to the formation of a trinuclear bicyclic [ClAl{(mu-O(c)Hex)(2)AlCl(2)}(2)] (3). Two polymorphic forms of 3 were isolated. Further coordination of cyclohexanol to the Lewis acidic five-coordinate aluminum atom in 3 provided [Cl(HO(c)Hex)Al{(mu-O(c)Hex)(2)AlCl(2)}(2)] (4) with octahedrally coordinated central aluminum. Compound 4 could be regarded as a precursor to the well-known Mitsubishi (tridiamond) tetranuclear species. The reactions of EtAlCl(2) with less sterically demanding (n)BuOH yielded a cyclic trimer, [Cl(2)Al(mu-O(n)Bu)](3) (5), and a unique trinuclear ionic species, [Cl(2)Al{(mu-OH)(mu-O(n)Bu)AlCl(HO(n)Bu)(3)}(2)]Cl (6) with a linear Al(mu-O)(2)Al(mu-O)(2)Al core. In the reactions with phenols, the aromatic groups preferentially stabilized dimeric structures of [Cl(2)Al(mu-OR)(2)AlCl(2)] (R = Ph, 7; 2,4-(t)Bu(2)C(6)H(3), 8). Since these compounds could be considered as intermediates in the nonhydrolytic condensation reactions of metal halides with metal alkoxides, a mixture of EtAlCl(2) with (c)HexOH was used as a precursor for the nonaqueous synthesis of alumina by alkylhalide elimination.
authors: Department of Chemistry, Masaryk University, Kotlarska 2, CZ-61137 Brno, Czech Republic.
authors: Zdenek
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