Isolation and detailed characterization of the trans-[(H2O)(2)FeCl4](-) anion: Stabilization of novel iron(III) species by large organic cations

1,2-Diaminoethane (en) and FeCl3 give (enH(2)) [FeCl5(H2O)] (1) in concentr ated HCl, extending the aquapentachloroferrate(III) series. For 1: C2H12N2C l5OFe, orthorhombic, P2(1)2(1)2(1), a = 14.531(6) Angstrom, b = 10.772(4) A ngstrom, c = 6.888(2) Angstrom, Z = 4. Diazabicyclo[2.2.2]octane dihydrochl oride (DABCO(.)2HCl) and FeCl3 in concentrated HCl form a tetrachloroferrat e(III) derivative whose subsequent ethanol treatment (restricted water acce ss) results in the formation of a compound of composition (DABCOH(2))(2) [F eCl4(H2O)(2)]Cl-3 (2). This contains the trans-[FeCl4(H2O)(2)](-) anion, in which the trans-Fe-O distances are 2.049(4) Angstrom. For 2: C12H32N4Cl7O2 Fe, orthorhombic, Pnma, a = 16.378(3) Angstrom, b = 7.3323(6) Angstrom, c = 19.431(3) Angstrom, Z = 4. A combination of Fe-57 Mossbauer spectroscopy a nd ac susceptibility data confirm uncanted 3D antiferromagnetic ground stat es with T-Neel similar to3.4 K for (enH(2-))[FeCl5(H2O)] and -2.0 K for [DA B COH2](2)[FeCl4(H2O)(2)] Cl-3.