Synthesis of aluminum hydrazides by hydroalumination of 2,3-diazabutadienes--formation of an Al4(N2)3 cage compound and an Al3(N2)3 macrocyclic ligand.

Abstract

Treatment of 1,1,4,4-tetramethyl-2,3-diazabutadiene with the alane adduct [AlH3(NMe2Et)] yielded the hydrazine derivative (AlH2)2-(AlH)2(N2iPr2)3 (1) by the hydroalumination of both C N double bonds. Compound 1 has a complicated cage structure formed by three hydrazido groups and four aluminium atoms. As a particularly interesting structural motif it contains a N-N group side-on-coordinated to one aluminium atom through its lone pairs of electrons. Sublimation of 1 gave a heterocubane-type compound (HAlNiPr)4 (2) by the complete cleavage of all N-N bonds, one face of which is bridged by weakly coordinated diisopropyldiazene with a N-N double bond. Repeated sublimation gave the pure, unsupported heterocubane molecule 3. Heating of the rough product of the reaction of alane and diazabutadiene to 90 degrees C in a closed vessel yielded another product Al(AlH2)3(N2iPr2)3 (4), which contains a cyclic chelating ligand formed by three hydrazido groups and three aluminium atoms. This heterocycle coordinates a fourth aluminum atom in the molecular center by close contacts to all six nitrogen atoms. A strongly flattened, distorted octahedral coordination sphere results for the inner metal atom.