Towards mid-valent rhenium fluoro-phosphine complexes via hexafluoridorhenate(IV) anion pathway assisted by trifluoro acetic acid

Abstract

The new (AsPh4)2[ReF6]·2H2O salt was prepared by metathesis from the reaction of (NH4)2ReF6 and (AsPh4)Cl in water and characterized by single crystal X-ray diffraction and UV–Visible spectroscopy. (AsPh4)2[ReF6]·2H2O crystallizes in the space group P1¯ (a = 10.0609(17) Å, b = 11.0577(18) Å, c = 21.184(4) Å, α = 75.974(2) °, β = 77.922(2) °, γ = 71.396(2) °). In (AsPh4)2[ReF6]·2H2O, the ReF62- anion exhibits a slightly distorted octahedral geometry with ReF = 1.9470(12) Å − 1.9693(13) Å and <FReF> = 88.44(6) ° − 91.88(6) °. The reaction of (AsPh4)2[ReF6]·2H2O with triphenylphosphine and trifluoroacetic acid in acetonitrile produced a new Re(+5) oxo-fluoride complexes, ReOF(OOCCF3)2(PPh3)2. ReOF(OOCCF3)2(PPh3)2 exhibits a distorted octahedral geometry and consists of a [ReOF]2+ core coordinated to two trans-PPh3 and two trans- CF3COO- ligands. In ReOF(OOCCF3)2(PPh3)2 , the F and O atoms are statistically disordered. The O/F position (ReO/F = 1.7947(23) Å) are equally occupied by 9-electron F atoms (ReF distance of 1.924(10) Å and 8-electron O atoms (ReO = 1.682(11) Å). The UV–Visible spectrum of ReOF(OOCCF3)2(PPh3)2 in acetonitrile is consistent with the one of Re(+5) oxo-complexes; it exhibits bands at 260 nm, 365 nm and 530 nm that has been respectively attributed to (P) → (Re) and (O) → (Re) transitions as well as transitions in the ligand field.