Preparation and Ignition Properties of Aluminum Alkyls

Abstract

Three years ago, a joint project was established by the Wright Aeronautical Division, Curtiss-Wright Corp., at the Jet and Flame Laboratory of New York University, to study the preparation and behavior of pyrophoric organometallic compounds. The aluminum alkyls have been one of the most interesting groups studied to date, from an ignition standpoint.Compounds capable of ready spontaneous ignition with air are of considerable potential importance for certain types of air-breathing power plants. Certain thermal theories of flame propagation suggest that the flame is propagated by virtue of continuous spontaneous ignition occurring on the leading edge of the flame front; in such a case, the time lapse before the flame appears-ignition delay-would be an important factor.Although aluminum alkyls have been known for some time, it has been only during the past few years that these compounds have been the subject of extensive research, largely because of the use of these compounds by Ziegler as catalysts for olefin polymerizations at low pressures. Preparation of Aluminum AlkylsA convenient method for the preparation of small quantities of these compounds involves a displacement reaction between aluminum metal and the alkyl compound of some less active metal (which can be readily prepared)-e.g., the reaction of dimethylmercury with an excess of aluminum yields trimethylaluminum and mercury (2) :Although this procedure gives good yields for lower members of the series, the decreased stability of the higher mercury alkyls limits its usefulness. The cost of such a method would be high.Recently Ziegler has developed several new methods of preparing aluminum alkyls using olefins as the starting reagents (10, 11).At about 100° C. lithium aluminum hydride reacts with ethylene and tetraethylaluminum lithium is formed:When this quaternary salt is treated with aluminum chloride, triethylaluminum is formed :This method has been used to prepare the corresponding η-propyl and n-hexyl com pounds.A more economical process for the large scale production of these compounds involves spraying aluminum into an atmosphere of hydrogen and an olefin (12): 172 METAL-ORGANIC COMPOUNDS Downloaded from pubs.acs.org by UNIV OF CALIFORNIA SAN DIEGO on 06/09/15. For personal use only.

Synthesis and Electrochemical Properties of Aluminum Hexafluorophosphate

“…Al­(PF 6 ) 3 was synthesized through the reaction between ammonium hexafluoro­phosphate (NH 4 PF 6 ) and triethylaluminum (Et 3 Al) as shown in reaction . The experimental details can be found in the Supporting Information. The selection of the solvent of this reaction was restricted by the compatibility with Et 3 Al and solubility of Al­(PF 6 ) 3 : Et 3 Al is very reactive toward olefinic groups, carbonyls, primary and secondary amines, hydroxyl groups, and so on . One may also anticipate that the especially strong Coulombic attraction between the trivalent Al 3+ and the PF 6 – anion renders it much more difficult for the ion solvation to sufficiently compensate for energy loss during the disruption of the rather stable Al­(PF 6 ) 3 lattice.…”

“…The selection of the solvent of this reaction was restricted by the compatibility with Et 3 Al and solubility of Al(PF 6 ) 3 : Et 3 Al is very reactive toward olefinic groups, carbonyls, primary and secondary amines, hydroxyl groups, and so on. 22 One may also anticipate that the especially strong Coulombic attraction between the trivalent Al 3+ and the PF 6 − anion renders it much more difficult for the ion solvation to sufficiently compensate for energy loss during the disruption of the rather stable Al(PF 6 ) 3 lattice. Eventually, we identify dimethyl sulfoxide (DMSO) as the only proper solvent that meets the above stringent requirements, with both good solvation power for Al(PF 6 ) 3 and chemical stability with Et 3 Al.…”

Synthesis and Electrochemical Properties of an Aluminum Hexafluorophosphate Electrolyte

“…The selection of the solvent of this reaction are restricted by the compatibility to Et3Al and the solubility of Al(PF6)3: Et3Al is very active towards olefinic groups, carbonyl groups, primary and secondary amine groups, and hydroxyl groups. 21 In addition, strong coulombic attraction between Al 3+ and the anion results to much lower solubility of Al(PF6)3 in comparison to its monovalent analog. Thereby, we found dimethyl sulfoxide (DMSO) may be the only proper solvent with good solubility of Al(PF6)3 and compatibility with Et3Al.…”