Electronically Strongly Coupled Divinylheterocyclic‐Bridged Diruthenium Complexes

Abstract

Complexes [{Ru(CO)Cl(PiPr3 )2 }2 (μ-2,5-(CH-CH)2 -(c) C4 H2 E] (E=NR; R=C6 H4 -4-NMe2 (10 a), C6 H4 -4-OMe (10 b), C6 H4 -4-Me (10 c), C6 H5 (10 d), C6 H4 -4-CO2 Et (10 e), C6 H4 -4-NO2 (10 f), C6 H3 -3,5-(CF3 )2 (10 g), CH3 (11); E=O (12), S (13)) are discussed. The solid state structures of four alkynes and two complexes are reported. (Spectro)electrochemical studies show a moderate influence of the nature of the heteroatom and the electron-donating or -withdrawing substituents R in 10 a-g on the electrochemical and spectroscopic properties. The CVs display two consecutive one-electron redox events with ΔE°'=350-495 mV. A linear relationship between ΔE°' and the σp Hammett constant for 10 a-f was found. IR, UV/Vis/NIR and EPR studies for 10(+) -13(+) confirm full charge delocalization over the {Ru}CH-CH-heterocycle-CH-CH{Ru} backbone, classifying them as Class III systems according to the Robin and Day classification. DFT-optimized structures of the neutral complexes agree well with the experimental ones and provide insight into the structural consequences of stepwise oxidations.

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

“…Gidron and Bendikov reported that oligofurans can offer stronger electronic coupling between ferrocenyl redox units than oligothiophenes . Similar results were obtained by Lang and co‐workers who used ruthenium or iron(II) complexes as redox‐active termini bridged by 2,5‐diethynylfuran and ‐thiophene , . However, in 2,5‐diethynylfuran‐ and ‐thiophene‐bridged bis(ferrocene) complexes, the thiophene derivative is likely modestly more strongly coupled .…”

“…The structures of related bimetallic divinylfuran and ‐thiophene ruthenium complexes have been recently reported , . However, complexes 4a – 4d represent the first crystallographically characterised examples of a systemic chalcogenophene series of binuclear complexes (Figure ).…”

“…Against this backdrop of long‐standing interest in the properties of bimetallic complexes featuring (oligo)thiophene‐based bridges, there has been increasing interest in genuine mixed‐valence compounds featuring oligofuran‐based bridging ligands . Gidron and Bendikov reported that oligofurans can offer stronger electronic coupling between ferrocenyl redox units than oligothiophenes .…”

“…Binuclear ruthenium mixed‐valence complexes incorporating two “RuCl(CO)(PR 3 ) 2 L” (L = neutral two‐electron donor or free coordination site) redox‐active termini connected by a carbon‐rich unsaturated spacer display well‐behaved redox chemistry and are ideally suited for studies of the electron‐density distribution and interplay between the properties of the bridge and metal centres as well as charge‐transfer characteristics , , , , , . In particular, the synergistic nature of the bonding interactions between the Ru metal centre and ancillary CO ligand results in the v (CO) IR band being an excellent reporter group of metal electron density , , .…”

(Planar‐Chiral) Ferrocenylmethanols: From Anionic Homo Phospho‐Fries Rearrangements to α‐Ferrocenyl Carbenium Ions

“…In situ UV/Vis/NIR spectroelectrochemical measurements were additionally carried out for 19 to prove, if the redox separation of 201 mV is due to an electronic communication between both ferrocenyls, as observed for 1,4‐diferrocenylbutadiene, or caused by electrostatic interactions. However, an inter‐valence charge transfer (IVCT) absorption in the region between 1250 and 2750 nm has not been observed (Figure SI6), revealing that the redox separation is due to electrostatic interactions and no electronic communication between the Fc and Fc + fragments occurred in the mono‐oxidized mixed‐valent species. The absence of an electronic communication between the both ferrocenyls in 19 might be supported by the non‐planar C=N–N = C moiety in the solid‐state structure (Figure ), due to a torsion angle of ca.…”