Über die Reaktion sekundärer Amine mit Lithiumtetrahydridoaluminat

Abstract

Abstract Lithium-tris(diethylamino)hydridoaluminate, Lithium-bis(diisopropylamino)dihydridoaluminate. Lithium(tetramethylpiperidino)trihydridoaluminate, NMR Spectra, X-Ray Reactions of diethylamine, diisopropylamine and 2,2,6,6-tetramethylpiperidine with LiAlH4 in various ethers have been studied. Only two well-defined products result from Et2NH, namely LiAlH(NEt2)- and LiAl(NEt2)4 . If molar ratios of Et2NH:LiAlH4 smaller than 3:1 are employed all compounds of the series LiAlH4-n(NEt2)n (n = 0, 1, 2, 3) are present in solutions of tetra-hydrofuran and diglyme. In diethylether insoluble materials consisting predominantly of lithium diethylaminohydridoaluminates and, presumably, small quantities of Li3AlH6 are also formed. At ambient temperature diisopropylamine reacts slowly with LiAlH4 , and LiAlH2(NiPr2)2 can be isolated as a well-defined substitution product. 2,2,6,6-tetramethylpiperidine (tmpH) replaces only a single hydride from LiAlH4 with formation of LiAlH3 (tmp). The reactions have been monitored by 7Li, 13C and 27Al NMR spectroscopy, and the structure of LiAlH(NEt2)3 has been determined by X-ray analysis. The monoclinic compound contains chains of AlHN3 and LiHN3 tetrahedra linked through common edges.