Isolation and characterization of nitrososulphide species (SNO? /SNOH) stabilized by coordination to iridium (III)

CRISTIÁN HUCK IRIART; ANA FOI; LEANDRO ANDRINI; JOSÉ RAMALLO LÓPEZ; Y. JOLY; FLORENCIA DI SALVO; FABIO DOCTOROVICH

Campinas

Otro; Annual Users Meeting LNLS/CNPEM; 2017

LNLS/CNPEM

Nitric oxide (NO) and hydrogen sulfide (H2S) aregaseotransmitters that regulate numerous physiological functions. Base on thesimilarity in their physiological effects, itis suggested a possible "link" between these two endogenous species[1]. Although theexistence of S-nitrosothiols (RSNO) in biological systems is known since 1992[2], theexistence of the simplest RSNO, the thionitrous acid (HSNO), was demonstratedinsolution in 2012 [3]. The study of the reaction between H2S and NO in thecontext ofcoordination chemistry was approached by Olabe et al., who studied the reactionofnitroprusside ([Fe(CN)5(NO)]2?) with HS?and detected formation of the species[Fe(CN)5N(O)SH]3? and then,[Fe(CN)5N(O)S]4?; both characterized in solution [4]. TheNO+ in the complex[IrCl5(NO)]? (1) is the most nucleophilic known to date,speciallydue to the weak backbonding. On the other hand, thanks to the inertness of the[IrCl5]?moiety, several N-nitroso derivatives(RXNO), highly instable species in their free form,were obtained by reaction of 1 with different nucleophiles and stabilized by coordinationto the metal centre [5]. This background motivated us to study the reaction of 1 withH2S/HS? as nucleophiles. The reaction was studied at both 25 °C and ?30 °C indifferentsolvents and using H2S(g), NaSH, and Na2S in acid medium as H2S/HS- sources. In allthe studied conditions, a red solid is immediately obtained as product. Theproduct wascharacterized by standard spectroscopic techniques (UV-vis, IR),low-temperature highresolution ESI-MS studies and X-ray Absorption Fine Structure (XAFS)spectroscopy atthe S K-edge and Ir L3-edge. The geometry of the proposed Ir complex was optimized byDFT calculation using ORCA. S K edge XANES and Ir L3 EXAFS were simulated usingFDMNES[6] and FEFF 9.6.4. The experimental and theoretical results show strongevidence of the stabilization of SNO?/SNOH species through coordination toIr(III). Thiswork includes evidences for the formation and isolation in solid form of a IrIII-SNOXcoordination complex which is unprecedented. Thus, this study opens the way tousetransition metals other than iron and ruthenium for S-nitrosylation of sulfidesusing NOand contributes to the understanding of species of physiological relevance.[1] Yang, G. et al. Science, 322. 587 −590 (2008)[2] Stamler, J. S.; Singel, D. J.; Loscalzo, J. Science, 258, 1898 −1902 (1992)[3] Filipovic, M. R. et al. J. Am. Chem. Soc. 134, 12016 −12027 (2012)[4]Quiroga, S. L.; Almaraz, A. E.; Amorebieta, V. ; Perissinotti, L. L. ; Olabe,J. Chem. Eur. J., 17, 4145? 4156 (2011)[5]Doctorovich, F.; Di Salvo, F. Acc. Chem. Res, 40 985 (2007)[6] Joly, Y Phys. Rev. B, 63, 125120 (2001)Acknowledgements: Authors wish to thanksCONICET, ANPCyT-MinCyT and LNLS.