The chemistry of covalent inorganic azides originated with the synthesis of aqueous HN3 solutions by Tony Curtis in 1890. A little later, in 1900, it proved possible to prepare iodine azide, IN3, as the first member of the meanwhile complete series of halogen azides. Since then it has been possible to synthesize, in addition to HN3 and the stable salt H2N 3+SbF 6−, azide compounds of elements from Groups 13 to 17. In these compounds the N3 moiety acts as a pseudohalogen and is primarily covalently coordinated to the nonmetal. Only a few organic azides, however, as well as HN3, H2N 3+, and all halogen azides have been thoroughly studied with respect to structure and bonding. The combined application of diffraction methods (X‐ray and electron diffraction) and microwave spectroscopy together with quantum chemical approaches such as ab initio SCF and density functional calculations have led in the last few years to an improved understanding of the molecular properties of numerous nonmetal azides, almost all of which are explosive. This interaction of theory and experiment has greatly enhanced the development of azide chemistry and has led to realistic expectations for the synthesis of as yet unknown nonmetal azides.

Die Chemie der kovalenten anorganischen Azide geht auf die Synthese wäßriger HN3‐Lösungen durch Tony Curtis im Jahr 1890 zurück. Wenig später, 1900, konnte bereits Iodazid IN3 als erstes Glied der heute vollständigen Reihe der Halogenazide hergestellt werden. Obwohl es gelungen ist, neben HN3 und dem stabilen Salz H2N3+SbF6− auch von Elementen der 13. bis 17. Gruppe Azidverbindungen herzustellen, in denen die N3‐Gruppe als Pseudohalogen fungiert und überwiegend kovalent an das jeweilige Nichtmetall gebunden ist, sind bis heute neben einigen organischen Azidverbindungen hauptsächlich HN3, H2N3+ und alle Halogenazide strukturell und bezüglich ihrer Bindungsverhältnisse eingehend studiert worden. Tatsächlich gelang es erst in den letzten Jahren durch Kombination von Beugungsmethoden (Röntgen‐ und Elektronenbeugung) und Mikrowellenspektroskopie mit modernen quantenchemischen Ansätzen wie Ab‐initio‐SCF‐ und Dichtefunktional‐Rechnungen, die Moleküleigenschaften etlicher, fast immer explosiver Nichtmetallazide besser zu verstehen. Gerade dieses Zusammenspiel von Theorie und Experiment hat die Weiterentwicklung der Azidchemie stark gefördert und der präparativen Synthese bisher nicht existenter Nichtmetallazide reale Chancen eröffnet.

COMMUNICATIONS the investigation of a wide variety of hydrogen-bonded supramolecular assemblies and more generally of self-assembly through any type of intermolecular interaction. Such work is currently in progress in our laboratory. Esprrim iw I ril Pr oc~durePositive-tori ES m a s 5pectr:i were obtained on a VG BioQ triple quadrupole apparatus xvith ;I m;i\s-to-charge (n!:) range up to 4000 (VG Bio Tech Ltd. Altrincham. U K ) . The clectrospray source was heated to 50 C. The sampling cone volkige ( 1 . ) 161 *:is a t 10 V to avoid fragmentation of the assemblies. Sample solutions were introduced into the mass spectrometer source ujith a syringe pump (Harvard type 55 I I 1 1 ; Harvard Apparatus Inc.. South Natick. MA. USA) at a flow rate o f 6 yI.min-I . Cdibration was performed using protonated horse myoglobin. The resolution bit\ usu;illy about 500 at in:: 1000 (10% height). Scanning was performed from m : 200 to 2200 in 15 s. The data system was operated as a multichannel analyier. and several scans were summed to obtain the final spectrum. Simples lor ESMS wcre prepared by dissolving equimolar amounts of the component\ in the appropriate solvent (dichloromethane. benzene. pentane) to achieve the concentrationa listed in Table 1 . Solutions containing salts were prepared by adding 0.5 mg of salt (KPF,,. NaCIO,, CsCI) iii 0.5 mL of solution and sonicating briefly. The soluti(iii was removed from the excess salt uith a pipette and directly analyzed. Labeling expel-imenb uere performed by adding the desired ratio of equimolar solutions of the iiiiictive label (A without KPF,) and the assembly of interest, and tlicn ;idding KPF,, 'is previously described. Keywords: crown ethers mass spectrometry . supramolecular chemistry [21] For studies at the rather high concentration (lo-' M) Compound B also gave satisfactory microanalytical data. Triazines A and C were not crystalline. and it was not possible to obtain satisfactory microanaly-

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