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

The complex [CpReI(CO)(2)(NO)](+) with Cp = cyclopentadienyl shows two long-wavelength absorptions at lambda(max) = 380 and 330 nm which are assigned to Re-I --> NO+ metal-to-ligand charge transfer (MLCT) transitions. In the solid state [CpReI(CO)(2)(NO)]PF6 displays a luminescence at lambda(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 PPh3, MLCT excitation leads to a photosubstitution yielding [CpRe(CO)(PPh3)(NO)](+). The dependence of the quantum yield on the PPh3 concentration is consistent with an associative mechanism. (C) 2002 Elsevier Science B.V. All rights reserved.