A Structurally Diverse Series of Aluminum Chloride Alkoxides [Cl x Al(μ-OR) y ] n (R = n Bu, c Hex, Ph, 2,4- t Bu2C6H3)

• Published in: Inorganic chemistry Vol. 48; no. 17; pp. 8106 - 8114
• Main Authors: Moravec, Zdenek, Sluka, Radek, Necas, Marek, Jancik, Vojtech, Pinkas, Jiri
• Format: Journal Article
• Language: English
• Published: American Chemical Society 07.09.2009
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic802251g

A diverse series of aluminum chloride alkoxides, [Cl x Al(μ-OR) y ] n (R = n Bu, c Hex, Ph, 2,4- t Bu2C6H3), was synthesized using the reactions of dichlorethylalane (EtAlCl2) with cyclohexanol ( c HexOH), n-butanol ( n BuOH), and phenols (PhOH and 2,4- t Bu2C6H3OH). Eight molecular products were isolated and structurally characterized. The dimeric [Cl2Al(μ-O c Hex)2AlCl2] (1) was the smallest oligomer isolated among the cyclohexanolate derivatives. The adduct of 1 with cyclohexanol is a dinuclear molecule [Cl2(HO c Hex)Al(μ-O c Hex)2AlCl2] (2) which represents a possible intermediate in the conversion reaction leading to the formation of a trinuclear bicyclic [ClAl{(μ-O c Hex)2AlCl2}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{(μ-O c Hex)2AlCl2}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 EtAlCl2 with less sterically demanding n BuOH yielded a cyclic trimer, [Cl2Al(μ-O n Bu)]3 (5), and a unique trinuclear ionic species, [Cl2Al{(μ-OH)(μ-O n Bu)AlCl(HO n Bu)3}2]Cl (6) with a linear Al(μ-O)2Al(μ-O)2Al core. In the reactions with phenols, the aromatic groups preferentially stabilized dimeric structures of [Cl2Al(μ-OR)2AlCl2] (R = Ph, 7; 2,4- t Bu2C6H3, 8). Since these compounds could be considered as intermediates in the nonhydrolytic condensation reactions of metal halides with metal alkoxides, a mixture of EtAlCl2 with c HexOH was used as a precursor for the nonaqueous synthesis of alumina by alkylhalide elimination.