14N nuclear magnetic resonance of covalent azides

Abstract

14N Chemical shifts are reported for hydrazoic acid, certain organic and organoarsenic azides, and a number of metal azido-complexes. The shifts are related where possible to the electronic characteristics of the atom or group to which the azide is covalently attached and to the mode of attachment.No spin-spin coupling effects are observed but the shifts provide some evidence for molecular association or azide exchange in the compounds Me2AsN, and Et,AsN,.The covalent character of the metal-azide bond is demonstrated by the appearance of three distinct 14N n.m.r. signals for each of the azido-complexes studied.

Probing Platinum Azido Complexes by 14N and 15N NMR Spectroscopy

“…[15] Within a series of metal azido complexes, it has been found that the coordination shift of N a compared to the free ligand correlates with the oxidation state and softness of the metal: Pb IV < Sn IV < Au III < Au I % Pd II < Pt II . [28] For Pt azido complexes, the coordination shift…”

Tetraphenylphosphonium Hexaazidoarsenate(V): The First Structurally Characterized Binary AsV-Azide Species

“…The assignment was made on the basis of examples given in the literature. [8] The N2 atom shows a sharp signal at d À 141.1, the N3 atom at d À 165.4, and the N1 atom, as expected, gives a very broad resonance at d À 256.2. In the 75 As NMR spectrum, 1 shows a resonance at d 4 (standard: KAsF 6 , d 0) and appears at significantly lower shift compared to the starting material [PPh 4 ][AsCl 6 ] (d À 392).…”

“…The thermal ellipsoids represent a 25 % probability. Selected bond lengths [] and angles[8]: As-N1 1.931(2), N1-N2 1.229(3), N2-N3 1.123(3); As-N1-N2 115.6(2), N1-N2-N3 173.6(3), N1-As-N4 91.5(1). [*] Prof. Dr. T. M. Klapötke, Prof. Dr. H. Nöth, Dipl.-Chem.…”

Preparation of Bioconjugates through an Ugi Reaction

“…To date, copper ± dioxygen adducts characterized by X-ray crystallography are a set comprised of a complex with trans-m-1,2-peroxo bridge (type A), [7] two model complexes for the O 2 -binding protein hemocyanin that feature a m-h 2 :h 2 -peroxo group (B), [5,8] and a mononuclear h 2 -superoxo copper(ii) compound (C). [9] In addition, a m 4 -peroxo coordination mode unique in copper chemistry, in which a peroxo group spans four copper(ii) ions (D), has been described by Krebs et al [10] Herein, we report a novel example of such unusual m 4 -peroxo coordination (E), as well as the X-ray crystallographic characterization of a structurally analogous complex in which the OÀO linkage is formally cleaved and replaced by two OH units, while at the same time the overall tetranuclear framework is fully conserved.…”

“…[6,7] To the best of our knowledge, Ugi reactions have so far been solely applied to the immobilisation of proteins by condensation of a protein with an isonitrile-modified solid support. [8] In order to apply the Ugi reaction to the preparation of bioconjugates of the aforementioned type we reacted two proteins, bovine serum albumin (BSA) 1 a and horseradish peroxidase (HRP) 1 b,c, under various conditions with different carboxylic acids 2, carbonyl compounds 3, isonitriles 4, and amines 5. [9] The free functional groups of both BSA and HRP were used in Ugi reactions, either as amine groups or carboxylic acids (for native proteins 1 a,b) or as aldehyde groups (for NaIO 4 oxidized HRP 1 c [10] ), to afford bioconjugates as shown in Scheme 1.…”