Closing the Gap: Synthesis of Three Isomeric N,N-Ditetrazolymethane Ligands and Their Coordination Proficiency in Adaptable Laser Responsive Copper(II) and Sensitive Silver(I) Complexes

Abstract

N,N-Substituted ditetrazolylalkanes are widely used molecules in the field of coordination chemistry and are known with different alkyl chain lengths. The missing fragment within this row is presented by the elementary methylene-bridged ditetrazoles. The three different isomers (di­(tetrazol-1-yl)­methane (1,1-dtm, 1), (tetrazol-1-yl)­(tetrazol-2-yl)­methane (1,2-dtm, 2), and di­(tetrazol-2-yl)­methane (2,2-dtm, 3)) were synthesized in a convenient one-step reaction. All of them were successfully incorporated as neutral ligands in 15 new energetic coordination compounds (ECC) based on Cu2+ and Ag+ as well as different anions (nitrate, picrate (PA), styphnate (TNR), trinitrophloroglucinate (TNPG), and perchlorate) revealing an extraordinary coordination behavior of the ligands compared to other 5H-ditetrazolylalkanes. All compounds were extensively characterized using single-crystal X-ray diffraction experiments, infrared spectroscopy (IR), elemental analysis (EA), and differential thermal analysis (DTA). Furthermore, the sensitivities were determined using standard techniques, and Hirshfeld surface calculations of the ligands were applied to explain their significant divergences to external stimuli. The ECC possess very good exothermic decomposition temperatures up to 242 °C. The ignition of all colored complexes was tested in laser experiments, and two copper­(II) perchlorate compounds showed promising results in classic initiation capability tests using pentaerythritol tetranitrate (PETN).

A Smart Access to the Dinitramide Anion – The Use of Dinitraminic Acid for the Preparation of Nitrogen‐Rich Energetic Copper(II) Complexes

“…These ligands possess the highest calculated gas phase enthalpies of formation and are therefore known to yield the most powerful coordination compounds. [ 13 , 14 ]…”

“…[15] The use of nitrogen-rich endothermic tri-and Chemistry-A European Journal tetrazole ligands increases the energetic character of the ECC and, therefore, several different mono-and ditetrazoles were selected. [13,14,20] Since dinitramide-based compounds are known to suffer from low thermal stability, [11] the main focus was on bridging molecules, such as 1,2,4-triazoles and ditetrazoles. [12] Since the further aim of this work was to increase the energetic character of the complexes, focus was also put on ligands like 1-AT, 1-AMT, 1,5-DAT, as well as with different dtm isomers (Scheme 2).…”

“…These ligands possess the highest calculated gas phase enthalpies of formation and are therefore known to yield the most powerful coordination compounds. [13,14] All used ligands (Scheme 2) were either purchasable (NH 3 , ATRI) or synthesized using literature known procedures. Tetrazole derivatives were either prepared by the reaction of alkyl halides (MAT, dtm, 2,2-dte, 1,2-dtp) or dimethyl sulfate (1-MTZ) with 1,5H-tetrazole [9b,13a,14,20a,21] and through ring closure reactions using sodium azide, triethyl orthoformate, and the respective alkyl amine or diamine (AET, AMT, 1,1-dte, idtp, dtb).…”

“…[13b,14] The major task that needs to be dealt with when synthesizing dinitramine complexes can be explained by the corresponding tetraammine copper(II) compound (2) presented in Figure 1. The coordination compound was already described in 2002 and, due to the impossible isolation of an elemental pure sample, was only examined by X-ray diffraction, 14 N NMR, and vibrational spectroscopy. [15] The reason for this is probably the reaction that precedes the formation of the complex.…”

“…Therefore, the focus should also lie on the incorporation of ligands that are known to enhance the performance of the complexes by their high positive heat of formation. [ 13b , 14 ]…”