Voltammetry of oxorhenium(V) complexes containing the [O=Re−OR] core and substituted pyridine ligands |
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Authors: | Grant N Holder Geoffrey A Monteith |
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Institution: | 1. Department of Chemistry, Appalachian State University, 28608, Boone, NC, USA
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Abstract: | Compounds of the general formula ORe(OR)Cl2(PPh3)2] and ORe(OEt)Cl2(PPh3)(py)], where R=alkyl or aryl and py=a substituted pyridine, were synthesized and their voltammetric behaviour investigated.
For the former, the electron-transfer mechanism was observed to be dependent on solvent. In dry MeCN, a quasi-reversible oxidation
and a reduction followed by a chemical reaction was observed. There were indications of nucleophilic attack on electrochemically
generated ORe(OEt)Cl2(PPh3)2]+, forming an unstable species whose reduction potentials were strongly dependent on the identity of the nucleophile. Voltammetric
and spectroscopic observations of the oxorhenium(V) alkoxypyridine complex indicate the pyridine to be labile in halogenated
hydrocarbon solvents but not in Me2CO, MeCN, or CCl4. Electrochemical generation of ORe(OEt)Cl2(PPh3)(ClxCyHz)]+ (x=1,2, or 3; y=1 or 2; z=2,3, or 4) appears to be followed by transfer of a hydrogen atom from the solvent to form (HO)Re(OEt)Cl2(PPh3)]+. Various pyridine complexes of this type were preparedvia substitution reactions under mild conditions. Varying the reaction conditions allowed the synthesis oftrans-dioxotetrapyridyl complexes in excellent yield. |
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