Electrochemical, Spectroscopic, and Theoretical Studies on Diethynyl Ligand Bridged Ruthenium Complexes with 1,3-Bis(2-pyridylimino)isoindolate

Abstract

A series of ruthenium acetylide complexes [Ru(BPI)(PPh3)2(CCR)] (BPI = 1,3-bis(2-pyridylimino)isoindolate; R = −C6H5 (2), −Cp2Fe (3a), −C6H4C6H4CCCp2Fe (3b)) and bis(acetylide)-linked binuclear ruthenium complexes [{Ru(BPI)(PPh3)2}2(CCRCC)] (R = none (4), 1,4-benzenediyl (5), 1,4-naphthalenediyl (6), 9,10-anthracenediyl (7)) were synthesized and characterized by ESI-MS spectrometry, IR, 1H and 31P NMR, and UV–vis–near-IR spectroscopy, and cyclic and differential pulse voltammetry. Oxidation of 3–7 with 1 equiv of ferrocenium perchlorate afforded the corresponding one-electron-oxidized complexes 3 +–7 +. In contrast to the case for 3a + , where spin density is localized at the Fe center due to moderate electronic communication between RuII and FeIII centers along the Ru–CC–Cp2Fe backbone, the spin density is primarily populated on Ru for 3b + without an appreciable electronic interaction between RuIII and FeII across the quite long bridging system RuCCC6H4C6H4CCCp2Fe. For bis(acetylide)-linked binuclear ruthenium complexes 4–7, electrochemical, UV–vis–near-IR spectral and TD-DFT computational studies reveal that electronic delocalization along the bridging RuCCRCCRu backbone is highly dependent on the R spacer. It is demonstrated that with the gradual increase of a π-conjugated system in aromatic R spacer, the electronic delocalization shows progressive enhancement along the Ru–CCRCC–Ru backbone due to an increasing participation of the bridging ligand. 4 + displays highly electronically delocalized behavior, whereas 5 +–7 + are on the borderline of electronic delocalization.

Electronic Structures of Divinylchalcogenophene‐Bridged Biruthenium Complexes: Exploring Trends from O to Te

“…In this regard, the bimetallic complexes [L n M(µ‐bridge)ML n ], in which two ostensibly redox‐active metal centres M supported by auxiliary ligands L are linked by a π‐conjugated bridging unit, have attracted considerable attention , . Consequently, bimetallic complexes featuring a wide variety of metal end‐caps and π‐conjugated bridges, including carbon‐rich chains such as oligoynyl, oligoenyl, aromatic hydrocarbons and heterocycles,, bridging ligands containing other main‐group elements, carboranes and even other metal units, have been prepared and studied.…”

Role of Substituents at 3‐position of Thienylethynyl Spacer on Electronic Properties in Diruthenium(II) Organometallic Wire‐like Complexes

“…The free π‐conjugated organic bridging ligands do not undergo any redox process in the potential window of 0.2 to 0.8 V following a similar electrochemical set up. The peak‐to‐peak separation ΔE 1/2 = E 1/2 (2)‐ E 1/2 (1) and the comproportionation constant K c =exp(ΔE 1/2 /25.69 at 298 K) are the two critical parameters to evaluate the electron transfer kinetics along the molecular backbones in redox conjugates . Complex 5 a exhibits two successive oxidation processes at E 1/2 of 0.053 V and 0.443 V. The potential difference (E pa –E pc ) of 79 and 87 mV respectively, for the individual reversible redox wave, supports one‐electron redox process.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…Metal vinylidene complexes were suggested as likely M a n u s c r i p t 106 intermediates in the ruthenium-catalyzed reductive anti-Markovnikov hydration of terminal alkynes and formic acid [1017]. Electrochemical oxidations of alkynylmetal complexes likely produce species with substantial metal carbon multiple bonding character [1018,1019,1020,1021,1022]. Enhanced resonance interaction from a vinylidene resonance form was noted when the phosphine group of a diphenylphosphinoethynyliron complex was ligated to palladium [1023].…”