Ruthenium nitrosyl complexes containing the Kläui's oxgyen tripodal ligand LOEt - ([CpCo{P(O)(OEt)2} 3]- where Cp = η5-C5H 5) were synthesized and their photolysis studied. The treatment of [Ru(NN)(NO)Cl3] with [AgLOEt] and Ag(OTf) afforded [L OEtRu(NN)(NO)][OTf]2 where NN = 4,4′-di-tert-butyl- 2,2′-bipyridyl (dtbpy) (2·[OTf]2), 2,2′-bipyridyl (bpy) (3·[OTf]2), N,N,N′N′- tetramethylethylenediamine (4·[OTf]2). Anion metathesis of 3·[OTf]2 with HPF6 and HBF4 gave 3·[PF6]2 and 3·[BF4]2, respectively. Similarly, the PF6 - salt 4·[PF 6]2 was prepared by the reaction of 4·[OTf] 2 with HPF6. The irradiation of [LOEtRu(NO) Cl2] (1) with UV light in CH2Cl2-MeCN and tetrahydrofuran (thf)-H2O afforded [LOEtRuCl 2(MeCN)] (5) and the chloro-bridged dimer [LOEtRuCl] 2(μ-Cl)2 (6), respectively. The photolysis of complex [2][OTf]2 in MeCN gave [LOEtRu(dtbpy)(MeCN)][OTf] 2 (7). Refluxing complex 5 with RNH2 in thf gave [L OEtRuCl2(NH2R)] (R = tBu (8), p-tol (9), Ph (10)). The oxidation of complex 6 with PhICl2 gave [L OEtRuCl3] (11), whereas the reduction of complex 6 with Zn and NH4PF6 in MeCN yielded [LOEtRu(MeCN) 3][PF6] (12). The reaction of 3·[BF 4]2 with benzylamine afforded the μ-dinitrogen complex [{LOEtRu(bpy)}2(μ-N2)][BF4] 2 (13) that was oxidized by [Cp2Fe]PF6 to a mixed valence RuII,III species. The formal potentials of the RuL OEt complexes have been determined by cyclic voltammetry. The structures of complexes 5,6,10,11 and 13 have been established by X-ray crystallography. © 2011 The Royal Society of Chemistry.