A spectroscopic investigation of some five-co-ordinate adducts of aluminium hydride with tetramethylmethylenediamine and tetramethylpropanediamine

Lewis base complexes of AlH3: prediction of preferred structure and stoichiometry

“…58 The TMMDA and TMPDA complexes of AlH 3 were studied by IR spectroscopy by Greenwood et al in 1968, although the TMEDA complex was not. 74 Our experimental and DFT frequencies for these complexes are very similar and agree with the literature values, apart from the symmetric and antisymmetric Al-H stretching modes calculated by DFT, which accords with our analysis of the AlH 3 •nTMA complexes (Table 7). The DFT calculations of these polymeric systems were carried out on a model system in which two ligands were attached to a central AlH 3 moiety.…”

“…The highly ordered, polymeric diamine-alane complexes melt at significantly higher temperatures than the corresponding molecular 1 : 1 or 1 : 2 adducts, as would be expected. For example, the complexes formed with TMPDA and TMEDA each have melting points above 135 °C, whilst that formed with N,N,N′,N′-tetramethylmethylenediamine (TMMDA) melts at 25-26 °C, 74 suggesting that this complex exists as a monomer, with the TMMDA chelating at one AlH 3 centre, rather than spanning two in a polymeric arrangement. On the basis of NMR spectroscopic experiments in benzene solution, Fetter et al also concluded that this complex was monomeric.…”