Synthesis and structural characterisation of unprecedented primary N-nitrosamines coordinated to iridium(iv).

The redox chemistry of the N-nitrosamine complexes [IrCl5(RN(H)N[double bond, length as m-dash]O)]2- (R = benzyl or n-butyl) was studied in detail. One-electron oxidations at around 200 mV vs. ferrocene/ferrocenium were reversible in cyclic voltammograms. UV-vis spectroelectrochemistry reveals spectra characteristic of IrIV species but also partial decomposition of the oxidised species [IrIVCl5(RN(H)N[double bond, length as m-dash]O)]˙- on this timescale (minutes). Detailed studies on chemically oxidised solutions of the parent IrIII complexes gave evidence for paramagnetic IrIV from NMR spectra. Final products of the decomposition were the corresponding alcohols and presumably [IrIIICl5(L)]2- (L = N2, solvent, amine) complexes. Similar decomposition reactions of acidic DMSO solutions of [IrCl5(RN(H)N[double bond, length as m-dash]O)]2-revealed that this combination produces the so-called "activated" DMSO (Me2S+-O- or Me2S+-OE, with "E" being an electrophile) which oxidises the parent IrIII complexes. Finally, with the very reactive purple IrIV compound (PPh4)[IrCl5(BnN(H)N[double bond, length as m-dash]O)], the first primary N-nitrosamine coordinated to [IrIVCl5]- was isolated and characterised by UV-vis absorption, FTIR, NMR spectroscopy, ultra-high resolution electrospray mass spectrometry (UHR-ESI-MS) and iridium L3 X-ray absorption near-edge spectroscopy (XANES).

The Me3 NB12 Cl11. Radical: A Strong One-Electron Oxidizing Agent.

Strong oxidizing agents often contain fluorine and are not compatible with substrates forming strong element-fluorine bonds. Therefore, there is need for new strong oxidizers. Cyclic voltammetric measurements on the weakly coordinating anion [Me3 NB12 Cl11 ]- in liquid SO2 revealed an oxidation wave at +2.59 V versus Fc0/+ . The oxidation of Na[Me3 NB12 Cl11 ] with AsF5 in liquid sulfur dioxide gives the boron-cluster-based radical Me3 NB12 Cl11. as a dark blue solid in quantitative yield. The radical was characterized by vibrational, NMR, and EPR spectroscopy and by its crystal structure. To explore the potential of the radical Me3 NB12 Cl11. to act as a strong oxidizing agent, it was reacted with different compounds having high ionization energies. Thianthrene (ionization energy 7.8 eV) and hexabromobenzene (8.8 eV) were oxidized to the corresponding cations. The reaction with elemental iodine (9.3 eV) gave the [I5 ]+ cation. These reactive cations are stabilized in the solid state by the weakly coordinating anion [Me3 NB12 Cl11 ]- , which was formed as a reduced product in the oxidation reactions.

Copper thiocyanato complexes and cocaine - a case of 'black cocaine'.

The chemical composition of a black powder confiscated by German customs was elucidated. Black powders are occasionally used as a 'transporter' for cocaine and are obviously especially designed to cloak the presence of the drug. The material consisting of cocaine, copper, iron, thiocyanate, and graphite was approached by analytical tools and chemical modelling. Graphite is added to the material probably with the intention of masking the typical infrared (IR) fingerprints of cocaine and can be clearly detected by powder X-ray diffraction (XRD) and Raman spectroscopy. Cu(2+) and NCS(-) ions, when carefully reacted with cocaine hydrochloride, form the novel compound (CocH)2 [Cu(NCS)4 ] (CocH(+) = protonated cocaine), which has been characterised by single crystal XRD, IR, NMR, UV/Vis absorption and EPR spectroscopy. Based on some further experiments the assumed composition of the original black powder is discussed.

A five-coordinate nickel(II) fluoroalkyl complex as a precursor to a spectroscopically detectable Ni(III) species.

Mechanistic proposals for nickel-catalyzed coupling reactions often invoke five-coordinate alkyl- or aryl-bound Ni(II) and/or high-valent nickel(III) species, but because of their reactive nature, they have been difficult to study and fingerprint. In this work, we invoked the stabilizing properties of fluoroalkyl ligands to access such nickel species bearing ligands that are commonplace in organic coupling reactions. We show that five-coordinate Ni(II) complexes containing nickel-carbon bonds can readily be prepared given the appropriate precursor, and we also present evidence for the formation of Ni(III) species upon chemical and electrochemical oxidation of the five-coordinate complexes.

Generation and characterisation of the phenoxyl-radical containing Cu(II) complex [Cu(triaz)2]+ (triaz- = O,N chelating triazole-phenolate).

The new copper complex [Cu(triaz)(2)] (Htriaz = 2,4-di-(tert-butyl)-6-(5-chloro-2H-benzo[d][1,2,3]triazol-2-yl)phenol) was investigated in detail by single crystal XRD, EPR-, UV/Vis-absorption-, CV-, and spectroelectrochemistry. The oxidised species [Cu(triaz)(2)](+) was characterised by UV/Vis spectroelectrochemistry and contains a phenoxyl-radical bound to Cu(II). This quite stable species was chemically generated by two different methods: aerial oxidation of a Cu(I) precursor in the presence of Htriaz (and base) or from [Cu(triaz)(2)] by adding a Cu(II) salt (disproportionation). The efficiency for the latter reaction has been studied by UV/Vis spectroscopy, XAS and catalytic test reactions (oxidation of benzyl alcohol).