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

Abstract

The reaction of AlMe 3 with (dme) 2Ca(NPh 2) 2 in a solvent mixture of toluene and THF yields the addition product [(thf) 6Ca] [Me 3Al–NPh 2] 2 ( 1). In solution the anion of this solvent-separated complex 1 [ δ( 27Al) = 153] partly dismutates into ([AlMe 2(NPh 2) 2] − [ δ( 27Al) = 179] and [AlMe 4] − [ δ( 27Al) = 155]. The [Me 3Al–NPh 2] − 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.