Synthesis and crystal structure of nitrosoruthenium complexes cis-[Ru(NO)Py2Cl2(OH)] and cis-[Ru(NO)Py2Cl2(H2O)]Cl. Photoinduced transformations of cis-[Ru(NO)Py2Cl2(OH)]

Abstract

The interaction of K₂[Ru(NO)Cl₅] with an excess of pyridine followed by concentration of the reaction solution afforded two crystalline modifications of cis-[Ru(NO)Py₂Cl₂(OH)] (1a and 1b). The treatment of this hydroxocomplex with hydrochloric acid gave an aquacomplex cis-[Ru(NO)Py₂Cl₂(H₂O)]Cl (2). The prepared complexes were characterized by elemental analysis, X-ray diffraction, infrared and ¹H NMR spectroscopies. Infrared and Raman spectroscopies provided evidence that irradiation of cis-[Ru(NO)Py₂Cl₂(OH)] (λ ∼ 450 nm, T = 80 K) resulted in photoisomerization with the formation of metastable states MS1 (isonitrosyl complex) and MS2 (η²-coordination of the NO). The population of the MS1 state amounts to 60%. Differential scanning calorimetry (DSC) was used to determine the activation parameters for MS1: E_a = 65.2(3) kJ mol⁻¹, k₀ = 1.05(7) × 10¹⁴ s⁻¹. These experimental data agree well with DFT calculations.