The reaction of Re2O7 with XeF6 in anhydrous HF provides a convenient route to high-purity ReO2F3. The fluoride acceptor and Lewis base properties of ReO2F3 have been investigated leading to the formation of [M][ReO2P4] [M = Li, Na, Cs, N(CH3)4], [K][Re2O4F7], [K][Re2O4F7]·2ReO2F 3, [Cs][Re3O6F10], and ReO2F3(CH3CN). The ReO2Pr, Re2O4F7-, and Re3O6F10- anions and the ReO2F3(CH3CN) adduct have been characterized in the solid state by Raman spectroscopy, and the structures [Li][ReO2F4], [K][Re2O4F7], [K][Re2O4F7]·2ReO2F 3, [Cs]-[Re3O6F10], and ReO3F(CH3CN)2·CH3CN have been determined by X-ray crystallography. [Li][ReO2F4] crystallizes in the tetragonal system, space group P4̄21m, with a = 4.727(3) Å, c = 8.880(7) Å, V = 198.4(7) Å3, and Z = 2 at 24 °C, R1 = 0.0378, and wR2 = 0.1029. [K][Re2O4F7] crystallizes in the monoclinic system, space group P2/n, with a = 5.4990(11) Å, b = 5.1530(10) Å, c = 14.753(3) Å, β= 95.68°, V = 415.99(14) A°3, and Z = 2 at 20 °C, R1 = 0.0473, and wR2 = 0.1200. [K][Re2O4F7]·2ReO2F 3 crystallizes in the monoclinic system, space group C2, with a = 27.32(2) Å, b = 5.274(5) Å, c = 5.355(3) Å, β= 99.53(4)°, V = 760.9(11) Å3, and Z =2 at -60 °C, R1 = 0.0238, and wR2 = 0.0645. [Cs][Re3O6F10] crystallizes in the triclinic system, space group P1̄, with a = 7.011(1) Å, b = 9.773(2) Å, c = 10.331(2) Å, α = 113.73(1)°, β = 91.05(2)°, γ = 92.42(2)°, V = 647.4(2) Å3, and Z = 2 at -118 °C, R1 = 0.0522, and wR2 = 0.0529. ReO3F(CH3CN)·CH3CN crystallizes in the orthorhombic system, space group Pnma, with a = 9.138(3) Å, b = 12.518(5) Å, V= 1045.4(7) Å3, and Z = 4 at -63 °C, R1 = 0.0198, and wR2 = 0.0605. The structure of ReO2F4- consists of a cis-dioxo arrangement of Re-O double bonds in which the Re-F bonds trans to the oxygen atoms are significantly lengthened as a result of the trans influence of the oxygens. The Re2O4F7- and Re3O6F10- anions and polymeric ReO2F3 are open chains containing fluorine-bridged ReO2F4 units in which each pair of Re-O bonds are cis to each other and the fluorine bridges are trans to oxygens. The trans influence of the oxygens is manifested by elongated terminal Re-F bonds trans to Re-O bonds as in ReO2F4- and by the occurrence of both fluorine bridges trans to Re-O bonds. Fluorine-19 NMR spectra show that ReO2F4-, Re2O4F7-, and ReO2F3(CH3CN) have cis-dioxo arrangements in CH3CN solution. Density functional theory calculations at the local and nonlocal levels confirm that the cisdioxo isomers of ReO2F4- and ReO2F3(CH3CN), where CH3CN is bonded trans to an oxygen, are the energy-minimized structures. The adduct ReO3F(CH3CN)2·CH3CN was obtained by hydrolysis of ReO2F3(CH3CN), and was shown by X-ray crystallography to have a facial arrangement of oxygen atoms on rhenium. © 1999 American Chemical Society.