Ligand-Induced Structural, Photophysical, and Electrochemical Variations in Tricarbonyl Rhenium(I) Tetrazolato Complexes

Treatment of [Re­(CO)5X] (X = Cl, Br) with 2-(2-tert-butyltetrazol-5-yl)­pyridine yielded neutral mononuclear
complexes by exchange of two CO ligands for the chelating tetrazolato
ligand. Treatment of [Re­(CO)5Br] with phenyltetrazolate
resulted in the assembly of an anionic dinuclear rhenium tricarbonyl
species bridged by three tetrazole rings. The reaction of [Re­(CO)5Br] with (2-tert-butyltetrazol-5-yl)­benzene
formed an analogous neutral dinuclear complex bridged by a tetrazole
ring as well as two bromide ligands; however this complex was found
to be rather unstable in solution and was only structurally characterized
via X-ray diffraction. The first three complexes were investigated
for their photophysical properties, highlighting phosphorescent emission
from their triplet metal-to-ligand charge transfer excited states,
although in the case of the dinuclear species the quantum yield was
found to be extremely low. The complexes are also characterized for
their electrochemical behavior, and while the neutral mononuclear
species show irreversible oxidations, the dinuclear complex displays
one reversible and simultaneous two-electron oxidation.