The dark blue title compound has been prepared by reaction of [Re,Cl8]2- and F-, both dissolved as ion pairs with [(n–C4H9)4N]+ in anhydrous CH2Cl2, and recrystallization from acetone/diethylether. Structure determination by single crystal X-ray diffractometry at 150 K reveals crystallization in the cubic system, space group Pn3̄n with a = 19.783(3)Å, V = 7742.4Å3, Z = 6. The {[Re2F8]·O(C,H5)2}2- entity consists of an axially elongated F8-cubane frame around the Re, unit, which is coordinated at one side by an ether molecule (Re–O distance 2.64(4)Å) and displaced from the center towards the ether. The Re– Re quadruple bond (2.188(3)A) is the shortest of the four octahalogenodirhenates(III). In contrast to its Cl, Br and I homologues no disorder of the Re, units is observed. The Re– F distances of 1.92(3) and 1.96(3)A are equal within the standard error, and the Re–Re–F angles are 99.9(4)⚪ and 102.6(4) , respectively. The UV-Vis spectrum of [(n–C4H9)4N]2[Re2F8] shows only the δ-δ* transition at 558 nm (ε = 771 cm2/mmol). At 10 K this band exhibits a weak vibrational fine structure with an averaged progression of 209 cm-1. The Raman spectrum is dominated by v(Re–Re) at 317.5 cm-1 with up to five overtones, the IR spectrum by v(Re–F) at 560 cm-1. Additional bands for the solvated compound at 525 and 306 cm-1 are assigned to v(Re–O) and v(Re–Re), respectively. The 19F NMR spectrum in aceton-d6 shows a singlet at –135.06 ppm; in the presence of ether an additional weak signal arises at –134.15 ppm versus external CFC13.
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