Near-Infrared-Absorbing Organometallic Diruthenium Complex Intermediates: Evidence for Bridging Anthrasemiquinone Formation and against Mixed Valency
| Autor: | Martina Bubrin, Karuppannan Natarajan, Thangavel Sathiya Kamatchi, Wolfgang Kaim, Thomas Michael Scherer, Sudipta Mondal |
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| Rok vydání: | 2017 |
| Předmět: |
010405 organic chemistry
Organic Chemistry Valency chemistry.chemical_element Bridging ligand General Chemistry Intervalence charge transfer 010402 general chemistry Photochemistry 01 natural sciences Catalysis Spectral line 0104 chemical sciences Ruthenium law.invention Absorbance Crystallography chemistry law Electron paramagnetic resonance Hyperfine structure |
| Zdroj: | Chemistry - A European Journal. 23:17810-17816 |
| ISSN: | 0947-6539 |
| DOI: | 10.1002/chem.201703888 |
| Popis: | The new redox-active complexes [RuH(CO)(EPh3)2(-Q2-)RuH(CO)(EPh3)2], E = P (1) and E = As (2) with the bis-chelate bridging ligand Q2- = 1,4-dioxido-9,10-anthraquinone were prepared and characterised. The related compound [RuCl(CO)(PPh3)2(-Qx2-)RuCl(CO)(PPh3)2] (4) with E = P and Qx2- = 5,8-dioxido-1,4-naphthoquinone 4 revealed trans-positioned PPh¬3 groups. The electrogenerated one-electron oxidised states 1+ and 2+ were examined using spectroelectrochemical techniques (EPR, IR and UV-vis-NIR). In situ EPR studies gave spectra with 31P or 75As hyperfine splitting of about 16 Gauss, small 99,101Ru coupling and small g anisotropy in the frozen solution state. The 31P and 75As hyperfine values reflect axial positioning of the four Ru-E bonds relative to the plane of an anthrasemiquinone bridge. Single CO stretching bands around 1910 cm-1 of the precursors 1 and 2 shift by about 25 cm-1 to higher energies on oxidation. The direction, uniformity and the extent of the shifts confirm ligand bridge-based oxidation. Absorbance in the near infrared region is thus assigned to intra-ligand transitions of ruthenium(II) bonded anthrasemiquinones and not to intervalence charge transfer of mixed-valent species. Ruthenium(II) stabilisation by CO and EPh3 is made responsible for the anthrasemiquinone formation instead of metal-centered oxidation. |
| Databáze: | OpenAIRE |
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