Synthesis, structural characterization, and magnetic properties of a new charge-transfer salt composed of polyoxotungstate acceptors [WVWVI5O19]3- and cationic ferrocenyl CpFe+ Cp donors

The crystal structure of the charge-transfer slat (CpFe+ Cp)(3)[(WW5O19)-W-V-O-VI] (CpFeCp = Fe(C5H5)(2)), synthesized from the reaction of Na2WO4 . 2H(2)O with ferrocene under acid conditions, has been determined by single-crystal X-ray diffraction. The crystal is of triclinic space group P(-1) with a = 13.0374( 3), b = 15.0406(3), c = 16.8239(1) Angstrom, alpha = 91.417(1), beta = 98.931(1), gamma = 115.294(1) degrees, V = 2931.20(9) Angstrom(3), Z = 1, M-r = 5895.57, F(000) = 2652, mu = 18.735 mm(-1), and D-c = 3.340 g . cm(-3). The final R factor is 0.0502 for 10173 (R-int = 0.0563) unique reflections and 770 parameters. The structural analysis reveals that there are two crystallographically distinct [(WW5O19)-W-V-O-VI](3-) polyoxoanions and six independent ferrocene cations per unit cell. Each polyoxoanion consists of six WO6 octahedra with three types of W-O bond lengths. Interestingly, CpFe+Cp moieties are stacked to form octagonal channels that incorporate the polyanions. The closest Fe ... Fe distances between the neighboring ferrocenyl cations are more than 6.49 Angstrom, therefore, a good magnetic isolation between the iron centers is expected.