Ruthenium Styryl Complexes with Ligands Derived from 2-Hydroxy- and 2-Mercaptopyridine and 2-Hydroxy- and 2-Mercaptoquinoline

Abstract

A series of ruthenium styryl complexes with potentially noninnocent κ 2 [N,O] − or κ 2 [N,S] − ligands have been prepared by treatment of 5-coordinated 16-valence-electron ruthenium styryl complexes Ru(CO)Cl(P i Pr 3 ) 2 (CHCH-C 6 H 4 -4R) with deprotonated bidentate 2-hydroxy-or 2-mercaptopyridines or 2-hydroxy-or 2-mercaptoquinolines. These 6-coordinated complexes have been characterized by NMR and IR spectroscopy and by cyclic voltammetry. Moreover, the structures of complexes 1d, 2a, 3c, 5b, and 6b have been established by X-ray crystallography. Our results indicate that the pyridine-derived complexes exist as two isomers that differ with respect to the orientation of the κ 2 [N,O] − or κ 2 [N,S] − donor ligands relative to the CO and alkenyl ligands in the equatorial plane. The equilibrium between the two isomers is thermodynamically controlled. Thus, the relative amount of the minor isomer increases at higher temperatures. With the 2-hydroxyquinoline-or 2-mercaptoquinoline-derived ligands only one isomer is observed. Electrochemical studies show that these complexes undergo one or two reversible consecutive one-electron oxidations, the potentials of which respond to the electronic properties of the 4-substituent at the styryl ligand and those of the ancillary chelate ligand. Strong ligand contributions to the first oxidation of the complexes were experimentally verified by IR and EPR spectroelectrochemistry. Quantum chemical calculations reproduce our experimental results, including the positions of the Ru(CO) vibrational bands of the neutral complexes and of their corresponding radical cations. Our combined results indicate that the oxidation of all complexes is dominated by the styryl ligand, irrespective of the electronic nature of the 4-substituent and of the [N,O] − or [N,S] − chelate ligand.

Oxidized Styrylruthenium–Ferrocene Conjugates: From Valence Localization to Valence Tautomerism

“…The other metrical data are unremarkable compared to those of closely related structures of five‐, , , , and six‐coordinate[3a], alkenylruthenium complexes with the Ru(CO)(P i Pr 3 ) 2 (L) moiety and warrant no further discussion. Owing to the strong σ‐ trans influence of the alkenyl ligand, the Ru–O bond opposite the latter ligand is longer than that opposite the carbonyl ligand by ca.…”

“…In further keeping with a sizable proportion of the latter VT, the electron paramagnetic resonance (EPR) spectrum of 2 ‐acac + in CH 2 Cl 2 solution shows a strong isotropic signal at g = 2.0542. [3a], , , , As the temperature decreases, the intensity of the signal decreases gradually until it almost vanishes at –120 °C (see Figure ). This indicates that the VT with the oxidized ferrocenyl moiety is the thermodynamically more favored one and that the other VT with an oxidized styrylruthenium moiety becomes increasingly populated on warming.…”

Redox‐Active Tetraruthenium Macrocycles Built from 1,4‐Divinylphenylene‐Bridged Diruthenium Complexes

“…The Ru atoms adopt their usual square‐pyramidal coordination geometry with the alkenyl ligand in the apical position, a mutual trans arrangement of the bulky phosphines and of the σ‐ and π‐donating chloro and the π‐accepting carbonyl ligand and a displacement of the Ru atom from the basal coordination plane towards the apical alkenyl ligand by 0.16 Å. The Ru‐C(CO), Ru‐Cl, Ru‐P as well as the Ru‐C(alkenyl) bond lengths present no peculiarities with respect to other complexes {Ru}−CH=CHR of the Ru(CO)Cl(P i Pr 3 ) 2 moiety ,. The Ru−Cl⋅⋅⋅H−CCl 3 interaction of 2.606 Å in 1‐OBu ⋅2 CHCl 3 is 0.344 Å shorter than the sum of the van der Waals radii, suggesting a strong hydrogen bond, but has no noticeable effect on the Ru−Cl bond length and other bond parameters in the immediate vicinity of the coordination centers.…”

“…As the “short” sides of the envisioned metallamacrocycles we chose benzene‐1,3‐ or pyridine‐3,5‐dicarboxylates as they provide the right spatial arrangement of the chelating carboxylate donors to generate closed cyclic structures and offer an easy means to introduce additional functionalities to subsequently link individual cages to larger arrays. Furthermore, carboxylates can easily replace the chloro ligands from Ru(CO)Cl(P i Pr 3 ) 2 (CH=CHR) precursors and provide a stable coordination towards the alkenyl ruthenium entity while avoiding the problem of formation of different isomers ( cis or trans with respect to the placement of the carbonyl and the alkenyl ligand in the equatorial plane) owing to their symmetry …”

“…Furthermore, we were interested to study the aspecto fi ntracage electronic coupling between identical, yet differently charged sides in their mixed-valent radicalc ations (one side oxidized, one in the neutrals tate) and trications (one side doubly oxidized, one singly oxidized). As the "short" sideso ft he envisioned metallamacrocycles we chose benzene-1,3-o rp yridine-3,5-dicarboxylates as they provide the right spatial arrangement of the chelating carboxylate donors to generate closed cyclic structures and offer an easy means to introducea ddi-tional functionalities to subsequently link individual cages to larger arrays.F urthermore, carboxylates can easily replacet he chloro ligands from Ru(CO)Cl(PiPr 3 ) 2 (CH=CHR) precursors and provide as table coordination towards the alkenyl ruthenium entityw hile avoiding the problem of formation of different isomers (cis or trans with respectt ot he placemento ft he carbonyl and the alkenyll igand in the equatorial plane) [13] owing to their symmetry. [11h, 14] We here report on the successful conversion of 1,4-divinylphenylene-bridgedd iruthenium complexes including an ew, even more electron-rich representative into tetraruthenium macrocycles by treatment with variousa rene dicarboxylate linkersa nd their electrochemical, structural ande lectronic properties along with the resultso fq uantum chemical studies on their variousr edox states.…”