Synthesis, structures and reactivity of ruthenium nitrosyl complexes containing Kläui's oxygen tripodal ligand

Abstract

Ruthenium nitrosyl complexes containing the Kläui's oxgyen tripodal ligand L_OEt⁻ ([CpCo{P(O)(OEt)₂}₃]⁻ where Cp = η⁵-C₅H₅) were synthesized and their photolysis studied. The treatment of [Ru(N⁁N)(NO)Cl₃] with [AgL_OEt] and Ag(OTf) afforded [L_OEtRu(N⁁N)(NO)][OTf]₂ where N⁁N = 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·[PF₆]₂ was prepared by the reaction of 4·[OTf]₂ with HPF₆. The irradiation of [L_OEtRu(NO)Cl₂] (1) with UV light in CH₂Cl₂-MeCN and tetrahydrofuran (thf)-H₂O afforded [L_OEtRuCl₂(MeCN)] (5) and the chloro-bridged dimer [L_OEtRuCl]₂(μ-Cl)₂ (6), respectively. The photolysis of complex [2][OTf]₂ in MeCN gave [L_OEtRu(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 [L_OEtRu(MeCN)₃][PF₆] (12). The reaction of 3·[BF₄]₂ with benzylamine afforded the μ-dinitrogen complex [{L_OEtRu(bpy)}₂(μ-N₂)][BF₄]₂ (13) that was oxidized by [Cp₂Fe]PF₆ to a mixed valence Ru^II,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.