Preparation and Structure of Rhenium Fluoride Trioxide ReO 3 F, and the Polymorphism of Rhenium Trifluoride Dioxide, ReO 2 F 3

The methods of preparation of ReO 3 F are revised. ReO 3 F 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 P 2/c. In presence of donor solvents ReO 3 F·2L ( L = (C 2 H 5 ) 2 O, (CH 3 ) 2 O, THF) are formed. ReO 2 F 3 , if crystallized from HF, exists in two crystalline forms, both are fluorine bridged chain polymers. (ReO 2 F 3 ‐I: a = 1539.7(3), b = 999.6(3), c = 924.4(2) pm, β = 95.25(1)°, space group P2 1 /c; ReO 2 F 3 ‐II: a = 544.9(1), b = 494.2(1), c = 1253.7(2) pm, β = 98.543(7)°, space group P 2 1 /c. ReO 2 F 3 crystallizes from CFCl 3 or SO 2 FCl as fluorine bridged cyclic trimer ( a = 881.4(4), c = 822.1(6) pm, γ = 120°, space group P 6 3 /m, or fluorine bridged cyclic tetramer ( a = 1107.8(2), b = 999.4(2), c = 1347.9(3) pm, space group C mca).