Synthesis of (Hydrazonido)aluminum Complexes

Abstract

Complexes [XAl{CH₂CR=NNMe₂}₂] {X = Cl and R = Me or iPr, X = Me and R = Me, and X = N(NMe₂)[CR=CH₂] and R = Me or iPr} were synthesized by salt metathesis reactions involving lithium salts of hydrazones, Li[CH₂CR=NNMe₂]. X-ray crystallographic studies showed that all the complexes contain two chelating hydrazonido ligands bonding to aluminum through the methylene carbon and amine nitrogen(–NMe₂). For the complexes in which X = N(NMe₂)[CR=CH₂] (R = Me or iPr), the N(NMe₂)[CR=CH₂] ligand represents a linkage isomer in which the hydrazonido ligand bonds through nitrogen rather than through carbon, thereby becoming a hydrazido ligand. In the single crystal containing [Al{CH₂CiPr=NNMe₂}₂{N(NMe₂)(CiPr=CH₂)}], its isomer [Al{CH₂CiPr=NNMe₂}₃], having two chelating hydrazonido and one monodentate hydrazonido ligands, is present 45 % of the time. In solution, the [Al{CH₂CR=NNMe₂}₂{N(NMe₂)(CR=CH₂)}] (R = Me or iPr) complexes are in equilibrium with [Al{CH₂CR=NNMe₂}₃]. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)