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 Re2L4F2 (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)[Re2F8]center dot 2H(2)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 [Re-2(hpp)(4)F-2]PF6 (3) was prepared from the one-electron oxidation of Re-2(hpp)(4)F-2 with [Cp2Fe]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 Re-2(hpp)(4)F-2 (1) is more easily oxidized than its chloro and bromo analogues.