The photochemistry of the W2(CO)10 2- complex was investigated with the goal of determining if irradiation of this dimer generates a powerful reducing agent, presumably a 19-electron species. In general, the photochemistry of the W2(CO)10 2- complex is comparable to that of other metal-metal-bonded carbonyl dimers. Irradiation into the low-energy tail of the d π → σ* electronic transition of the W2(CO)10 2- complex led to W-W bond homolysis. The resulting 17-electron W(CO)5 - radicals could be trapped with suitable ligands such as 4-cyanopyridine to give "19-electron adducts". (See ref 3 for an important definition of the phrase "19-electron adduct".) Evidence is presented that the ligands PPh3 and PBu3 also react with photogenerated W(CO)5 - to form adducts: W(CO)5 - + PR3 → W(CO)5PR3 -. These adducts are powerful reducing agents, and they were used to reduce CO2 to formate and CO. The only organometallic product formed in the reaction was W(CO)5PPh3, the oxidized form of the 19-electron complex. In a similar manner, Mn2(CO)10 was reduced to Mn(CO)5 -, Cp2Co+ to Cp2Co, benzophenone to the radical anion, and methylviologen (MV2+) to MV+. Alternative reduction mechanisms involving the W(CO)5 - radical, W(CO)5 2-, or HW2(CO)10 - as reductants were shown not to be operating. Nineteen-electron complexes generated by irradiation of Cp2Mo2(CO)6 proved incapable of reducing CO2.
|Number of pages||6|
|Publication status||Published - 1989|
ASJC Scopus subject areas
- Inorganic Chemistry