A NEW TETRANUCLEAR IRON(III) COMPLEX WITH AN [FE4O2] CORE - SYNTHESIS, STRUCTURE AND MOSSBAUER STUDIES OF [FE4(MU-3-O)2(MU-O2CCH3)6CL2(3-MEPY)4].CH3C=N(3-MEPY=3-METHYLPYRIDINE)

Hexakis(mu-acetato)bischlorotetrakis(3-methylpyridine)bis(mu3-oxo)tetrairon(III) acetonitrile, [Fe4Cl2(C2H3O2)6O2(C6H7N)4].C2H3N, M(r) = 1094. 1, triclinic, P1BAR, a = 11.236 (2), b = 11.709 (3), c = 19.897 (4) angstrom, alpha = 75.55 (2), beta = 81.02 (1), gamma = 78.92 (2)-degrees, V = 2471 (i) angstrom3, Z = 2, D(x) = 1.471 g cm-3 lambda(Mo Kalpha) = 0.71073 angstrom, mu = 13.2 cm-1, F(000) = 1124, room temperature, R = 0.045 for 6551 reflections with I > 3sigma(I). The title compound contains a tetrairon core linked by bridging oxygen and acetate ions. Each of the octahedrally coordinated iron(III) atoms is bonded to 3-methylpyridine, three mu-acetates and at least one mu3-oxygen. Two Fe atoms are also coordinated by chlorides while the other two are additionally coordinated by another mu3-oxygen. Mossbauer results indicate two quadrupole splittings in accordance with the two types of iron coordination spheres. The quadrupole splittings of 1.04 and 0.67 mm s-1 are assigned to the chloride- and non-chloride-bonded Fe atoms, respectively. [Fe4Cl2(C2H3O2)6O2(C6H7N)4].C2H3N Molecules of acetonitrile are incorporated in the crystal.