Synthesis and molecular structure of hexakis(tetrahydrofuran)calcium bis[trimethyl-(diphenylamino)alanate]

The reaction of AlMe3 with (dme)2Ca(NPh2)2 in a solvent mixture of toluene and THF yields the addition product [(thf)6Ca] [Me3Al–NPh2]2 (1). In solution the anion of this solvent-separated complex 1 [δ(27Al) = 153] partly dismutates into ([AlMe2(NPh2)2]− [δ(27Al) = 179] and [AlMe4]− [δ(27Al) = 155]. The [Me3Al–NPh2]− anion shows a strong backdonation of negative charge from the nitrogen atom into one phenyl ring whereas the other phenyl group forms hyperconjugative bonds between the p-orbital of the ipso-carbon atom and the σ∗(Al–C) orbital leading to a slight elongation of one of the Al–C bonds.