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

• Published in: Dalton transactions : an international journal of inorganic chemistry 2018-08, Vol.47 (33), p.11445-11454
• Main Authors: Foi, Ana, Salvo, Florencia Di, Doctorovich, Fabio, Huck-Iriart, Cristián, Ramallo-López, José Martín, Dürr, Maximilian, Ivanovi -Burmazovi, Ivana, Stirnat, Kathrin, Garbe, Simon, Klein, Axel
• Format: Article
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c8dt02549e

The redox chemistry of the N -nitrosamine complexes [IrCl 5 (RN(H)N&z.dbd;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 Ir IV species but also partial decomposition of the oxidised species [Ir IV Cl 5 (RN(H)N&z.dbd;O)]&z.rad; − on this timescale (minutes). Detailed studies on chemically oxidised solutions of the parent Ir III complexes gave evidence for paramagnetic Ir IV from NMR spectra. Final products of the decomposition were the corresponding alcohols and presumably [Ir III Cl 5 (L)] 2- (L = N 2 , solvent, amine) complexes. Similar decomposition reactions of acidic DMSO solutions of [IrCl 5 (RN(H)N&z.dbd;O)] 2- revealed that this combination produces the so-called "activated" DMSO (Me 2 S + -O − or Me 2 S + -OE, with "E" being an electrophile) which oxidises the parent Ir III complexes. Finally, with the very reactive purple Ir IV compound (PPh 4 )[IrCl 5 (BnN(H)N&z.dbd;O)], the first primary N -nitrosamine coordinated to [Ir IV Cl 5 ] − was isolated and characterised by UV-vis absorption, FTIR, NMR spectroscopy, ultra-high resolution electrospray mass spectrometry (UHR-ESI-MS) and iridium L 3 X-ray absorption near-edge spectroscopy (XANES). The one electron oxidation of the N -nitrosamine complexes [Ir III Cl 5 (RN(H)N&z.dbd;O)] 2- (R = benzyl or n -butyl) was studied in detail.