Multistep redox sequences of azopyridyl (L) bridged reaction centres in stable radical complex ions {(μ-L)[MCl(η5-C5Me5)]2}˙+, M = Rh or Ir: spectroelectrochemistry and high-frequency EPR spectroscopy
- 28 July 2003
- journal article
- Published by Royal Society of Chemistry (RSC) in Dalton Transactions
- No. 17,p. 3370-3375
- https://doi.org/10.1039/b305311c
Abstract
The dinuclear complex cations {(μ-L)[MCl(η5-C5Me5)]2}n, M = Rh or Ir and L = abpy (= 2,2′-azobispyridine) or abcp (= 2,2′-azobis(5-chloropyrimidine)), could be isolated as paramagnetic hexafluorophosphates (n = 1+) or, for M = Ir, as diamagnetic bis-hexafluorophosphates (n = 2+). In addition to the reversible one-electron process as indicated by this convertibility there are two successive chloride-releasing reduction steps, separated by unusually large potential differences ΔEEC between 0.75 V (Rh2/abpy) and 1.14 V (Ir2/abcp), leading to the spectroelectrochemically characterised complexes {[(η5-Me5C5)M](μ-L)[MCl(η5-C5Me5)]}+ and (μ-L)[M(η5-C5Me5)]2. This large splitting of ΔEEC establishes the capability of azopyridyl bridges for mediating efficient metal–metal communication beyond mere electron transfer. The neutral complexes (μ-L)[M(η5-C5Me5)]2 are distinguished by a series of intense absorption bands in the near infrared, the lowest absorption energies being displayed by the Ir2/abcp combination. The stable electron reservoir intermediates {(μ-L)[MCl(η5-C5Me5)]2}+ were identified as complexes of L˙− anion radicals via their small g anisotropy as measured through high-frequency (>200 GHz) EPR spectroscopy.Keywords
This publication has 46 references indexed in Scilit:
- Resolving the Two-Electron Process for the Couple [(C5Me5)M(N∧N)Cl]+/[(C5Me5)M(N∧N)] (M = Rh, Ir) into Two One-Electron Steps Using the 2,2‘-Azobis(pyridine) N∧N Ligand, Fast Scan Cyclovoltammetry, and Spectroelectrochemistry: Detection of Radicals instead of MIIIntermediatesOrganometallics, 2003
- 2,5-Bis(1-phenyliminoethyl)pyrazine (bpip): a conjugated metal–metal bridging acceptor ligand and its homodinuclear complexes with low-valent metal centresJ. Chem. Soc., Dalton Trans., 1999
- Pulled Molecular Strings and Stacked Molecular Decks: Chelate-Ring Formation vs. Metal–Metal Bridging in Dicopper(I) Complexes of 2,2′-Bipyrimidine with Diphosphine Ligands of Variable Polymethylene Chain LengthChemistry – A European Journal, 1996
- Chemical Redox Agents for Organometallic ChemistryChemical Reviews, 1996
- Electronic Structure of π-Conjugated Redox Systems with Borane/Borataalkene End GroupsInorganic Chemistry, 1996
- Electronic Structure of the 16 Valence Electron Fragments M(CO)3(PR3)2 (M = Mo, W; R = iPr, Cy) in Their Complexes with H2, THF, and Three .pi.-Conjugated Dinucleating Ligands: Electrochemistry and Spectroscopy of Different Oxidation StatesInorganic Chemistry, 1995
- Chemical and Electrochemical Generation of Hydride-Forming Catalytic Intermediates (bpy)M(CnRn): M = Rh, Ir (n = 5); M = Ru, Os (n = 6). Coordinatively Unsaturated Ground State Models of MLCT Excited States?Inorganic Chemistry, 1994
- Structural consequences of electron-transfer reactions. 26. Evidence for time-dependent valence detrapping in a mixed-valent dimanganese fulvalenyl cationJournal of the American Chemical Society, 1993
- Kantenverknüpfung zweier Metallchelat‐Fünfringe: Strukturen und Magnetismus von Mo0‐, CuI‐ und CoII‐ Komplexen mit dem „S‐Frame”︁‐Liganden Azo‐2,2′‐pyridinZeitschrift für anorganische und allgemeine Chemie, 1991
- What determines the comproportionation constant in molecule-bridged mixed-valence complexes? Evidence for the crucial role of the ligand LUMO in four ruthenium(II)ruthenium(III) dimersInorganic Chemistry, 1988