Quadruply-bonded rhenium(III) dimers with the stoichiometry Re2L4F2 (L = hexahydro-2H-pyrimido[1,2a]pyrimidinate (hpp-) 1, and diphenyl formamidinate (dpf-) 2) were prepared from the solid-state melt reactions (SSMRs) between (NH4)2[Re2F8]●2H2O and HL. Those compounds were characterized in the solid-state by single crystal X-ray diffraction and in solution by UV-Visible spectroscopy and cyclic voltammetry. The compound [Re2(hpp)4F2]PF6 (3) was prepared from the one-electron oxidation of Re2(hpp)4F2 with [Cp2Fe]PF6. The compounds (1 to 3) are isostructural to the corresponding chloro derivatives. The redox properties of Re2L4X2 (X = F, Cl, Br) were studied by cyclic voltammetry. For Re2(hpp)4X2, the cyclic voltammograms exhibit two reversible oxidation waves corresponding to the formation of molecules with Re27+ and Re28+ cores. The CV of Re2(dpf)4F2 reveals a one electron reduction process which corresponds to the formation of the Re25+ core. The nature of the halogen has an effect on the redox properties: the Re2(hpp)4F2 complex is easier to oxidize than its heavier halogen analogs. The complexes were also studied by UV-Visible spectroscopy, the low energy band in their electronic spectra was assigned to δ→δ* transitions. In Re2L4X2, the position of δ→δ* transition is shifted to higher energy for X = F; the magnitude of the shift shows that the halogen has weak effect on the electronic structure of the Re26+ core.Dinuclear technetium complexes coordinated to fluoro ligand are still unknown; we plan to transpose the reactions used to prepare (NH4)2Re2F8 and Re2L4F2 to technetium and prepare (NH4)2Tc2F8 and Tc2L4F2.

Rhenium metal-metal bonded fluoro complexes

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.