Photoinduced linkage isomers in a model ruthenium nitrosyl complex: Identification and assignment of vibrational modes

Photoinduced NO-linkage isomers were investigated in the solid state of labelled trans-[Ru(^14/15NO)(py₄)F](ClO₄)₂ complex by combined IR-spectroscopy and DFT calculations. Based on the experimental data and the DFT calculations of this isotopically labelled ^14/15NO nitrosyl compound, we present a complete assignment of the vibrational bands of three nitrosyl linkage isomers in a range from 4000 to 200 cm^-1. The calculated IR-spectra match well with the experimental data allowing reliable assignment of the vibrational bands. The structural change from the Ru-NO (GS) to the Ru-ON (MS1) and Ru-η²-(NO) (MS2) linkage configuration leads to the downshift of the ν(NO) and ν(Ru-(NO)) bands, and a corresponding increase of the energy of the ν(Ru-F) band. The shift of the bands corresponds to the change of the Ru-(NO) and Ru-F bond lengths: increase of the Ru-(NO) bond length leads to the decrease of the energy of the ν(Ru-(NO)) band; decrease of the Ru-F bond length leads to the increase of the energy of the ν(Ru-F) band. These observations can be extrapolated to the family of related nitrosyl complexes and therefore be used for the qualitative prediction of the Ru-(NO) and Ru-L_trans-to-NO bond lengths of different linkage isomers in the framework of one complex. While the formation of linkage isomers is a reversible process, long-time irradiation sometimes induces irreversible reactions such as the release of NO. Here, we show that the photolysis of trans-[Ru(^14/15NO)(py₄)F](ClO₄)₂ in KBr pellets may lead to the release of nitrous oxide N₂O, conceivably through the formation of a {Ru-(κ²-ONNO)} intermediate.

Synthesis, structure and reactivity of NO+, NO˙ and NO- pincer PCN-Rh complexes

Synthesis of a pincer-type linear nitrosyl complex [Rh(P^tBu₂CN^Et₂)(NO)]⁺ (3⁺) is described. The product and all intermediates involved were fully characterized by FTIR, NMR, cyclic voltammetry and X-ray crystallography. Attempts at obtaining (3⁺) from its chlorinated precursor Rh(PCN)(NO)Cl (2) revealed that a relative stabilization of this complex ion is introduced by the BArF^- counteranion, as other counteranions-PF₆^-, BF₄^- and triflate-proved to coordinate to the metal center. Redox reactivity both of (3⁺) and of that of its five-coordinate derivatives (2) and [Rh(PCN)(NO)(CH₃CN)]⁺ (4⁺) was found to distinguish itself from analogous PCP complexes due to a relative stabilization of higher oxidation states. Oxidation of these three complexes was studied by FTIR spectroelectrochemistry. Reduction of complex (3⁺) to yield a short-lived {RhNO}⁹ species [Rh(PCN)(NO)]˙ (3˙) was also carried out. Complex (3˙) was proved able to activate carbon-halogen bonds in aryl halides, in much a similar way as that of its PCP analogue. Complex (3⁺) was also seen to establish a linear ↔ bent nitrosyl equilibrium upon addition of CO which could not be fully displaced with excess CO.

NO disproportionation over defective 1T′-MoS2 monolayers

NO disproportionation can be catalyzed by MoS₂ monolayers loaded with S vacancies. When the MoS₂ sheet is under 3% compressive strain, two NO molecules at a S vacancy can form a NO₂. The left N atom will react with a third NO to afford N₂O under 3% tensile strain.