Electronic spectra and photoreactivity of (cyclopentadienyl)rhenium(I)(dicarbonyl)(nitrosyl) cation

Abstract

The complex [CpRe I(CO) 2(NO)] + with Cp=cyclopentadienyl shows two long-wavelength absorptions at λ max=380 and 330 nm which are assigned to Re I→NO + metal-to-ligand charge transfer (MLCT) transitions. In the solid state [CpRe I(CO) 2(NO)]PF 6 displays a luminescence at λ max=570 nm which is assumed to originate from the lowest-energy Re I→NO + MLCT triplet. In solution the complex is not emissive but photoreactive. In the presence of PPh 3, MLCT excitation leads to a photosubstitution yielding [CpRe(CO)(PPh 3)(NO)] +. The dependence of the quantum yield on the PPh 3 concentration is consistent with an associative mechanism.