A Structurally Diverse Series of Aluminum Chloride Alkoxides [Cl_xAl(μ-OR)_y]_n (R = ⁿBu, ^cHex, Ph, 2,4-^tBu₂C₆H₃)

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.

Chelate Restrained Boron Cations for Intermolecular Electrophilic Arene Borylation

“…The 27 Al NMR spectra of this reaction consisted of two broad resonances, at 104 and 60 ppm, in the regions expected for four-and five-coordinate aluminum, respectively. [42][43][44] Slow cooling of a toluene solution of CatBCl and AlCl 3 (1:3 equiv, heated at 100 °C for two days) led to the deposition of a small quantity of yellow needles. X-ray diffraction analysis revealed a product derived from arene borylation and extensive ligand redistribution, comprised of a borylated catechol coordinated to two AlCl 2 and one AlCl 3 (compound 2, Figure 2 bottom).…”

The Power of Non-Hydrolytic Sol-Gel Chemistry: A Review

“…An example of alkyl halide elimination, alcohol route, was reported by Moravec et al [146]. The reactions between dichloroethylalane, EtAlCl2, and cyclohexanol, n butanol, phenol, and 2,4-di t butylphenol at low temperatures yielded a wealth of various aluminum chloride alkoxides, eight of which were structurally characterized.…”

Organoaluminum Initiators: Influence of Al Coordination on Polymerization and Product Properties

“…Phenoxide bridges are formed instead. According to a well defined dimeric structure may be expected, but our NMR results indicate that the product formed here is not uniform. At low phenol concentrations some precipitate is formed but when the phenol concentration exceeds the ethyl group concentration, a clear solution is obtained.…”