Zinc Hydrazide and Zinc Alkoxide Hydrazide Cages with Zn4N8 and Zn4N6O Cores – Cluster Isomerism as a Result of Subtle Changes in Ligand Size

Abstract

AbstractThe hydrazide cluster [(iPrZn)4(NHNMe2)4] (1) was synthesised by the reaction of diisopropylzinc with N,N‐dimethylhydrazine and was characterised by 1H‐ and 13C NMR and IR spectroscopy, mass spectrometry, elemental analysis and X‐ray crystallography. This compound forms asymmetric aggregates containing Zn4N8 cores. The Zn atoms in these aggregates are arranged in topological tetrahedra in which the triangular faces are bridged by NHNMe2 substituents. Each NH group is connected to two Zn atoms and each NMe2 group to one Zn atom. Alkoxide clusters were prepared in one‐pot syntheses by treating diisopropylzinc solutions with mixtures of N,N‐dimethylhydrazine and ROH (R = Et, iPr). The resulting compounds have the formula [(iPrZn)4(NHNMe2)3(OR)] [R = Et (3), iPr(4)] and contain Zn4N6O cages, such that one NHNMe2 in 1 is replaced by one alkoxide group. Two different aggregation modes were found for these Zn4N6O cages. In compound 3, one Zn atom is bound to two NMe2 groups and one NH group. The other three Zn atoms each have three bonds to NH groups and one dative bond to an NMe2 group. The cage consists of one four‐membered and one six‐membered ring as well as four five‐membered rings. In compound 4, the fourth zinc atom is exclusively bonded to three anionic NH functions in such a way that the rings in the cage are all five‐membered. Compounds 3 and 4 were characterised by NMR spectroscopy and single‐crystal X‐ray diffraction. Hydrazide hydroxide clusters were also obtained through the reaction of a diisopropylzinc solution with N,N‐dimethylhydrazine and a small amount of water. The structure of the resulting cocrystalline material, [(iPrZn)4(NHNMe2)4]·[(iPrZn)4(NHNMe2)3(OH)] (2), was also confirmed by X‐ray diffraction. The hydroxide cluster in 2 contains a Zn4N6O cage, with a similar aggregation mode to that of 4. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)