Jellyfish-type Dinuclear Hafnium Azido Complexes: Synthesis and Reactivity

Di- and multinuclear hafnium complexes bridged by ligands have been rarely reported. In this article, a novel 3,5-disubstituted pyrazolate-bridged ligand LH5 with two [N2 N]2- -type chelating side arms was designed and synthesized, which supported a series of dinuclear hafnium complexes. Dinuclear hafnium azides [LHf2 (μ-1,1-N3 )2 (N3 )2 ][Na(THF)4 ] 3 and [LHf2 (μ-1,1-N3 )2 (N3 )2 ][Na(2,2,2-Kryptofix)] 4 were further synthesized and structurally characterized, featuring two sets of terminal and bridging azido ligands like jellyfishes. The reactivity of 3 under reduction conditions was conducted, leading to a formation of a tetranuclear hafnium imido complex [L1 Hf2 (μ1 -NH)(N3 ){μ2 -K}]2 5. DFT calculations revealed that the mixed imido azide 5 was generated via an intramolecular C-H insertion from a putative dinuclear HfIV -nitridyl intermediate.

N-aryloxide-amidinate group 4 metal complexes

A N-aryloxide-amidine ligand (H3L), integrating phenoxide (PhO-) and amidine ligands through methylene linkers, has been synthesized from 2-(aminomethyl)-6-(tert-butyl)phenol in two steps. Upon reacting the deprotonated H3L ligand with group 4 metal chloride MIVCl4, a corresponding (LMIV-Cl)2 dimer could be obtained. The coordination modes exhibit variation depending on the radius of the metal ions. In the case of (LTiIV-Cl)2, the two ArO- arms from the same ligand bond to two different Ti(IV) centers, while in the case of (LZrIV/HfIV-Cl)2, both ArO- arms coordinate with the same metal center. Moreover, the two C-N bonds in the amidinate moiety are localized in (LTiIV-Cl)2, whereas they delocalize in (LZrIV-Cl)2. Notably, (LHfIV-Cl)2 could further react with one equivalent of HfCl4, yielding the binuclear metal azide in the presence of KN3 and LiCl, where the coordination mode of the amidinate moiety changed from the bidentate chelating type to the bimetallic bridging coordination.

Refinement of Copper(II) Azide with 1-Alkyl-5H-tetrazoles: Adaptable Energetic Complexes

A concept for stabilizing highly sensitive and explosive copper(II) azide with 1-N-substituted tetrazoles is described. It was possible to stabilize the system by the use of highly endothermic, nitrogen-rich ligands. The sensitivities of the resulting energetic copper coordination compounds can be tuned further by variation of the alkyl chain of the ligands and by phlegmatization of the complexes with classical additives during the synthesis. It is demonstrated, using the compound based on 1-methyl-5H-tetrazole ([Cu(N3 )2 (MTZ)], 1) that this class of complexes can be applied as a potential replacement for both lead azide (LA) and lead styphnate (LS). The complex was extensively investigated according to its chemical (elemental analysis, single-crystal and powder X-ray diffraction, IR spectroscopy, scanning electron microscopy) and physico-chemical properties (differential thermal analysis, sensitivities towards impact, friction, and electrostatic discharge) compared to pure copper(II) azide.