Synthesis of [RuCl2(NO)2(THF)] and its double C-N bond-forming reactions with alkenes.

While the activation of relatively inert gases such as N2 and CO with organometallic complexes remains a topic of intense investigation, methods for controlling the reactivity of nitric oxide at transition-metal centers have received considerably less attention. For example, the migratory insertion of NO into metal–alkyl or metal–aryl bonds has been observed in only a handful of metal complexes, despite the analogous reaction of CO dominating its organometallic chemistry and being the key step in many homogeneous catalytic processes. Although the paucity of studies in this field may be a reflection of the often complicated background reactivity of NO, the potential to develop selective reactions incorporating NO that form new carbon–nitrogen bonds represents an attractive approach in organic synthesis. It is in this context that we are interested in the ligandbased reaction of metal nitrosyl complexes with alkenes. In the absence of metal coordination the reaction chemistry of NO with alkenes is unruly. Furthermore, only a few transition-metal complexes have been shown to promote this reaction selectively. Thus, inspired by an early finding of Brunner and Loskot, we demonstrated in the 1980s that [{CpCo(NO)}2], NO and strained or alkyl-substituted alkenes react cleanly to form the corresponding dinitrosoalkane complexes [1, Eq. (1)]. More recently this chemistry has been used to develop a method for C C bond formation. In addition, the reaction of K[IrCl5(NO)] with alkenes to yield iridium nitrosoalkane complexes, and the reaction of [TpRuCl2(NO)] (Tp= tris(pyrazolyl)borate) with 2-vinylpyridine to yield a nitrosoalkene complex have been reported. In spite of the above reactions, there are not many C N bond-forming reactions of metal nitrosyls and double additions remain especially rare. We now report an example of this type of reactivity with the novel dinitrosyl complex [RuCl2(NO)2(THF)], which binds alkenes to the nitrosyl nitrogen atoms at room temperature in the presence of an additional neutral chelating ligand, L2. The reaction of [{(cymene)RuCl2}2] with 10 equiv of norbornadiene under an atmosphere of nitric oxide in [D8]THF gave a putative six-coordinate ruthenium dinitrosoalkane adduct [(THF)2RuCl2{(m-NO)2(C7H8)}] in 86% yield as evidenced by H NMR spectroscopy (Scheme 1).