An unusual oxo-bridged mixed-valent dinuclear rhenium complex with the Re centers in various different coordination environments

The [{ReCl4(PPh3)}(μ-O){Re(O)(3,5-Me2pzH)4}] complex has been isolated as a product of the degradation of [ReCl3(3,5-Me2pzH)2(PPh3)] during slow crystallization from chloroform in air. Its crystal and molecular structure has been determined, as well as spectroscopic investigations and density functional theory (DFT) calculations have been carried out. Additional information about binding in [{ReCl4(PPh3)}(μ-O){Re(O)(3,5-Me2pzH)4}] has been obtained by NBO analysis. The UV-Vis spectrum of the dirhenium complex has been discussed on the basis of the spin-allowed electronic transitions calculated for [{ReCl4(PPh3)}(μ-O){Re(O)(3,5-Me2pzH)4}] with the time-dependent DFT (TDDFT) method.