Effect of ionising radiation on potassium pentacyanonitrosylruthenate(II): an Electron Spin Resonance study

Abstract

O sal pentacianonitrosilrutenato(II) de potássio, em forma amorfa, foi sintetizado e caracterizado por espectroscopias UV, IR, difração de raios X e análise termogravimétrica. Amostras irradiadas por raios X revelam, por espectroscopia de Ressonância Paramagnética Eletrônica, a presença de complexos paramagnéticos de rutênio (I) e de radicais NO 2. Os parâmetros do hamiltoniano de spin medidos para o complexo [Ru(CN) 5 NO] 3-(g ⊥ = 2.0064, A ⊥ (14 N) = 60.7 MHz, g || = 1.999, A || (14 N) = 77.3 MHz) indicam uma captura eletrônica em um orbital molecular π* do grupo nitrosil com a participação de orbitais d xz and d yz do rutênio, como recentemente previsto por cálculos teóricos. Íons de prata, presentes como impurezas oriundas da rota sintética, são reduzidos a Ag(0) durante a irradiação e interagem com quatro nitrogênios equivalentes em um sítio distorcido, originando um espectro de RPE anisotrópico. Amorphous potassium pentacyanonitrosylruthenate (II) was synthesized and characterized by UV, IR, X-ray diffraction and thermogravimetric analysis. Electron Spin Resonance spectroscopy reveals the presence of paramagnetic ruthenate (I) complexes and NO 2 radicals in the X-irradiated diamagnetic salt. Spin-hamiltonian parameters of the [Ru(CN) 5 NO] 3complex (g ⊥ = 2.0064, A ⊥ (14 N) = 60.7 MHz, g || = 1.999, A || (14 N) = 77.3 MHz) support an electron capture in a π* molecular orbital of the nitrosyl group mixed with d xz and d yz ruthenium orbitals as recently predicted by theoretical calculations. Silver ions, present as impurities, are reduced to Ag(0) by X-irradiation and coordinate to four magnetically equivalent nitrogens in a distorted site, giving rise to a well resolved anisotropic ESR powder spectrum.

Coordination and Organometallic Chemistry of Metal−NO Complexes

“…Rather, there is evidence for dimerization of the trianion . The current view is that the unpaired electron density lies mainly on the nitrosyl ligands in these anions, thus formulated as [M II (CN) 5 (NO • )] 3- (M = Fe, Ru, Os). ,− The complex [ trans -Ru(Cl)(cyclam)(NO)] 2+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) forms [ trans -Ru(Cl)(cyclam)(NO • )] + when reduced by one electron at low temperature, and the extra electron resides on the NO ligand in the product in a manner similar to that observed for [Ru(CN) 5 (NO)] 3- . Light-induced metastable states have also been studied in octahedral Ru II nitrosyl complexes containing oxalate and ethylenediamine ligands …”