A tetrameric structure of the crystalline material was verified by NMR spectroscopy and X-ray crystallography. The species is described by the formula Al[(μ-O-i-Pr)2Al(O-i-Pr)2]3.[2][3] The unique central Al is octahedral, and three other Al centers adopt tetrahedral geometry. The idealised point group symmetryisD3.
This compound is commercially available. Industrially, it is prepared by the reaction between isopropyl alcohol and aluminium, or aluminium trichloride:
2 Al + 6 iPrOH → 2 Al(O-i-Pr)3 +3H2
AlCl3 + 3 iPrOH → Al(O-i-Pr)3 + 3 HCl
The procedure entails heating a mixture of aluminium, isopropyl alcohol, with a small amount of mercuric chloride. The process occurs via the formation of an amalgamof the aluminium. A catalytic amount of iodine is sometimes added to initiate the reaction.[4] The industrial route does not use mercury.[5]
Aluminium isopropoxide is used in MPV reductions of ketones and aldehydes and the Oppenauer oxidation of secondary alcohols.[6] In these reactions, it is assumed that the tetrameric cluster disaggregates. It is used in the Tishchenko reaction.
Aluminium isopropoxide was first reported in the master's thesis of the Russian organic chemist Vyacheslav Tishchenko (Вячеслав Евгеньевич Тищенко, 1861–1941), which was reprinted in the Journal of the Russian Physico-Chemical Society (Журнал Русского Физико-Химического Общества) of 1899.[8] This contribution included a detailed description of its synthesis, its peculiar physico-chemical behavior, and its catalytic activity in the Tishchenko reaction (catalytic transformation of aldehydes into esters). It was later found also to display catalytic activity as a reducing agent by Meerwein and Schmidt in the Meerwein–Ponndorf–Verley reduction ("MPV") in 1925.[9][10] The reverse of the MPV reaction, oxidation of an alcohol to a ketone, is termed the Oppenauer oxidation. The original Oppenauer oxidation employed aluminium butoxide in place of the isopropoxide.[11]
^Folting, K.; Streib, W. E.; Caulton, K. G.; Poncelet, O.; Hubert-Pfalzgraf, L. G. (1991). "Characterization of aluminum isopropoxide and aluminosiloxanes". Polyhedron. 10 (14): 1639–46. doi:10.1016/S0277-5387(00)83775-4.
^Turova, N. Y.; Kozunov, V. A.; Yanovskii, A. I.; Bokii, N. G.; Struchkov, Yu T.; Tarnopolskii, B. L. (1979). "Physico-chemical and structural investigation of aluminium isopropoxide." J. Inorg. Nucl. Chem.41(1): 5-11, doi:10.1016/0022-1902(79)80384-X.
^Tian, D.; Dubois, Ph.; Jérôme, R. (1997). "Macromolecular Engineering of Polylactones and Polylactides. 22. Copolymerization of ε-Caprolactone and 1,4,8-Trioxaspiro[4.6]-9-undecanone Initiated by Aluminum Isopropoxide". Macromolecules. 30 (9): 2575–2581. doi:10.1021/ma961567w.
^Oppenauer, R. V. (1937).『Eine Methode der Dehydrierung von Sekundären Alkoholen zu Ketonen. I. Zur Herstellung von Sterinketonen und Sexualhormonen』[Dehydration of secondary alcohols to ketones. I. Preparation of sterol ketones and sex hormones]. Recl. Trav. Chim. Pays-Bas (in German). 56 (2): 137–144. doi:10.1002/recl.19370560206.
