Preparation and Structure of Rhenium Fluoride Trioxide ReO3F,and the Polymorphism of Rhenium Trifluoride Dioxide,ReO2F3

The methods of preparation of ReO₃F are revised. ReO₃F is an amorphous yellow solid that crystallizes into colorless needles after prolonged heating. Its structure is that of a fluorine and oxygen bridged chain with hexa coordinated rhenium atoms (a = 670.9(2), b = 596.6(2), c = 1030.6(4) pm, β = 90.057(7)°, space group P2/c. In presence of donor solvents ReO₃F·2L (L = (C₂H₅)₂O, (CH₃)₂O, THF) are formed. ReO₂F₃, if crystallized from HF, exists in two crystalline forms, both are fluorine bridged chain polymers. (ReO₂F₃‐I: a = 1539.7(3), b = 999.6(3), c = 924.4(2) pm, β = 95.25(1)°, space group P2₁/c; ReO₂F₃‐II: a = 544.9(1), b = 494.2(1), c = 1253.7(2) pm, β = 98.543(7)°, space group P2₁/c. ReO₂F₃ crystallizes from CFCl₃ or SO₂FCl as fluorine bridged cyclic trimer (a = 881.4(4), c = 822.1(6) pm, γ = 120°, space group P6₃/m, or fluorine bridged cyclic tetramer (a = 1107.8(2), b = 999.4(2), c = 1347.9(3) pm, space group Cmca).