Expanding the Chemistry of Rhenium Metal-Metal Bonded Fluoro Complexes: Facile Preparation and Characterization of Paddlewheel Complexes.

Quadruply bonded rhenium(III) dimers with the stoichiometry Re2 L4 F2 (1, L = hexahydro-2H-pyrimido[1,2a]pyrimidinate (hpp- ); 2, L = diphenyl formamidinate (dpf- )) were prepared from the solid-state melt reactions (SSMRs) between (NH4 )2 [Re2 F8 ]·2H2 O 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)4 F2 ]PF6 (3) was prepared from the one-electron oxidation of Re2 (hpp)4 F2 with [Cp2 Fe]PF6 . Compounds 1-3 are isostructural with the corresponding chloro derivatives. In solution, compound 1 undergoes two one-electron oxidations. Comparison with its higher halogen homologues reveals that Re2 (hpp)4 F2 (1) is more easily oxidized than its chloro and bromo analogues.