Cycloruthenated Complexes from Imine‐Based Heterocycles: Synthesis, Characterization, and Reactivity toward Alkynes

Abstract

Novel cycloruthenated complexes 2 a-c, 4 a-c, and 6 a, b based on heteroaromatic cores have been synthesized by reaction of a series of heterocycle-based imines with [{RuCl(η(6)-p-cymene)}(2)(μ-Cl)(2)] and Cu(OAc)(2). This approach has proved efficient for the cyclometalation of thiophene, benzothiophene, furan, benzofuran, pyrrole, and indole derivatives. In addition, even a double cyclometalation process over the same heterocyclic ring is possible, yielding unprecedented bimetallic complexes. These ruthenacycles react with 3-hexyne through an unexpected pathway, which involves the coupling of the original imino heterocycle and acetylene followed by dearomatization to afford fused hetero-hydropyridyl ligands bonded to the {Ru(p-cymene)} organometallic moiety (i.e., 7 a-c and 8 a-c). These complexes represent, as far as we know, the first examples of this type of compound within the context of cyclometalation, and an exhaustive analysis of their structure was carried out in solution and solid state. Furthermore, these unique species react with CuCl(2), which promotes the rearomatization and the release of highly valuable aromatic fused bis-heterocycles (i.e., 9 a-c, 10 a-c, 11 a, and 12 a/12 a'), providing a novel and appealing synthetic route to this extraordinary family of molecules.

Syntheses and properties of cyclometalated ruthenium(II) complexes with 1,10-phenanthroline and phenylphthalazine ligands

“…In the past two decades, cycloruthenated complexes have been shown to be organometallic molecules useful for several interesting applications in various fields of chemistry, physics or biology owing to the strong σ-donor ability of the cyclometalating ligands [1][2][3]. For examples, they have been found to be important intermediates in the ortho functionalization of arenes via C-H activation [4], efficient dyes in dye-sensitized solar cells [5] and precatalysts for some certain processes, especially the asymmetric reduction of ketone and imines [6].…”

Rollover Cyclometalation as a Valuable Tool for Regioselective C–H Bond Activation and Functionalization

“…A third case of rollover metal-mediated C–H bond functionalization involves a series of ruthenium complexes with cyclometalated imines-based heterocycles [ 119 ]. The reaction of [{RuCl(h 6 - p -cymene)}(m-Cl) 2 ] with a series of imines-based heterocyclic ligands ( 129 ) in the presence of Cu(OAc) 2 ( Figure 63 ) resulted in the rollover cyclometalation due to C–H bond activation in the C(3) position of the five-membered heterocyclic ring (thiophene, benzothiophene, furan, benzofuran, pyrrole, and indole derivatives) affording rollover complexes 130 .…”

Nickel(II) complexes with mono(imino)pyrrole ligands: preparation, structure and ethylene polymerization behavior

“…Although a number of mono(imino)pyrrole ligands were developed, nearly all of the reported ligands bore H side arms [10][11][12][13][14][15][16]. We have expanded this work to mono(imino) pyrrole ligands with a -CH 3 side arm in order to have greater electronic and steric effects.…”

“…The corresponding iron, cobalt, and nickel complexes showed the catalytic activities to olefin polymerization. Cuesta et al [16] studied the reactivities of mono(imino)pyrrole, mono(imino)thiophene, and mono (imino)furan with [{RuCl(η 6 -p-cymene)} 2 (μ-Cl) 2 ], resulting in interesting structures.…”