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

Ana Foi; Florencia Di Salvo; Fabio Doctorovich; Cristián Huck-Iriart; José Martín Ramallo-López; Maximilian Dürr; Ivana Ivanović-Burmazović; Kathrin Stirnat; Simon Garbe; Axel Klein

doi:10.1039/C8DT02549E

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

Ana Foi,^a Florencia Di Salvo,*^a Fabio Doctorovich,

*^a Cristián Huck-Iriart,

^bc José Martín Ramallo-López,^b Maximilian Dürr,^d Ivana Ivanović-Burmazović,^d Kathrin Stirnat,^e Simon Garbe^e and Axel Klein

*^e

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* Corresponding authors

^a Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, INQUIMAE-CONICET, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
E-mail: flor@qi.fcen.uba.ar, doctorovich@qi.fcen.uba.ar

^b Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CONICET, Casilla de Correo 16, Sucursal 4, 1900 La Plata, Argentina

^c Escuela de Ciencia y Tecnología, CONICET, Universidad Nacional de San Martín (UNSAM), Campus Miguelete, 25 de Mayo y Francia, 1650 San Martín, Provincia de Buenos Aires, Argentina

^d Lehrstuhl für Bioanorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 1, 91058 Erlangen, Germany

^e University of Cologne, Department of Chemistry, Institute for Inorganic Chemistry, Greinstrasse 6, D-50939 Cologne, Germany
E-mail: axel.klein@uni-koeln.de

Abstract

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 Ir^IV species but also partial decomposition of the oxidised species [Ir^IVCl₅(RN(H)N [double bond, length as m-dash] O)]˙⁻ 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^IIICl₅(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 Ir^III complexes. Finally, with the very reactive purple Ir^IV compound (PPh₄)[IrCl₅(BnN(H)N [double bond, length as m-dash] O)], the first primary N-nitrosamine coordinated to [Ir^IVCl₅]⁻ 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).

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

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

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