SYNTHESIS AND MAGNETIC-PROPERTIES OF BINUCLEAR IRON(III) COMPLEXES WITH OXALATE, 2,5-DIHYDROXY-1,4-BENZOQUINONE DIANION, AND SQUARATE AS BRIDGING LIGANDS - CRYSTAL-STRUCTURE OF (MU-1,3-SQUARATO)BIS[(N,N'-ETHYLENEBIS(SALICYLIDENEAMINATO))(METHANOL)IRON(III)]

Three iron(III) complexes of formulas [Fe2(salen)2ox]·H2O (1), [Fe2(salen)2dhbq]·1.5H2O (2), and [Fe2(salen)2(CH3OH)2sq] (3), where salen = N,N′-ethylenebis(salicylideneaminate) (Cl6H14N2O22−), ox = oxalate (C2O42−), dhbq = the dianion of 2,5- dihydroxy-1,4-benzoquinone (C6H2O42−), and sq = the dianion of 3,4-dihydroxy-3-cyclobutene-1,2-dione (C4O42−), have been prepared. The crystal structure of 3 has been solved at room temperature. It crystallizes in the monoclinic system, space group P21/a, with a = 13.278 (3) Å, b = 14.464 (3) Å, c = 9.574 (2) Å, β = 96.24 (2)°, and Z = 2. The structure consists of μ-1,3-squarato-bridged [FeIII(salen)CH3OH)] binuclear units. The iron(III) is hexacoordinate, with the four donor atoms of salen and two oxygen atoms, one of a methanol molecule and the other of the squarate bridge, building a distorted octahedron around the metal ion. The magnetic behavior of all three complexes has been studied in the 4.2-300 K temperature range. The HDVV, (Ĥ = −JŜ·Ŝ2), S1 = S2 = 5/2 spin-exchange model applied to the measured magnetic susceptibilities vs temperature yields J values of −7.1, −0.92, and −0.39 cm−1 for 1-3, respectively. A discussion about the pathway of exchange interaction in this series is presented. © 1990, American Chemical Society. All rights reserved.