Reactivity of triethylaluminum with a series of secondary amines. Adduct and aminoalane dimer synthesis and characterization; the crystal structures of [Et2AlN(c-C6H11)(2)](2) and [Et2AlNC4H8NCH3](2)

The reactions of triethylaluminum with a series of 13 secondary amines (RH= HNMe2, HNEt2, HNPr2n, HNPr2i, HNBu2n, HNBu2i, HNBu2s, HNC4H8, HNC5H10, HNC6 H12, HN(c-C6H11)(2), HN(CH2Ph)(2), and HNC4H8NMe) afford room-temperature s table, clear, colorless liquid complexes. These complexes were characterize d by H-1 and C-13 NMR, IR and elemental analyses. Trends in the NMR chemica l shift data are compared with data previously reported fos the analogous t rimethylaluminum, -gallium, and -indium compounds in terms of the steric pr operties of the amines. Subsequent thermolysis of these complexes yields di meric aminoalanes via 1,2-elimination of ethane in all cases. The dimers we re characterized by H-1 and C-13 NMR, IR, melting point, cryoscopic molecul ar weight determinations, and elemental analyses. The NMR chemical shift da ta are compared with known data for the [Me2AlR](2) and [Me2GaR](2) series. The molecular structures of [Et2AlN(c-C6H11)(2)](2) and [Et2AlNC4H8NCH3](2 ), obtained from X-ray crystal data, are presented and discussed in terms o f the correlations between the structural parameters of the Al2N2 ring and the nature of the Al and N substituents. (C) 1999 Elsevier Science Ltd. All rights reserved.