Heterobimetallic Oxalato-Bridged M^IIRe^IV Complexes (M = Mn, Fe, Co, Ni): Synthesis, Crystal Structure, and Magnetic Properties

Four rhenium(IV)−M(II) bimetallic complexes of formula [ReCl4(μ-ox)M(dmphen)2]·CH3CN with M = Mn (1), Fe (2), Co (3), and Ni (4) (ox = oxalate anion, dmphen = 2,9-dimethyl-1,10-phenanthroline) have been synthesized and the crystal structures of 1 and 3 determined by single-crystal X-ray diffraction. 1 and 3 are isostructural and crystallize in the monoclinic system, space group P21/c, with a = 16.008(4) Å, b = 12.729(2) Å, c = 18.909(5) Å, β = 112.70(2)°, and Z = 4 for 1 and a = 15.998(4) Å, b = 12.665(2) Å, c = 18.693(5) Å, β = 112.33(2)°, and Z = 4, for 3. The structure of 1 and 3 is made up of neutral [ReCl4(μ-ox)M(dmphen)2] bimetallic units (M = Mn (1), Co (3)) and acetonitrile molecules of crystallization. M(II) and Re(IV) metal ions exhibit distorted octahedral coordination geometries being bridged by a bis(bidentate) oxalato ligand. The magnetic behavior of 1−4 has been investigated over the temperature range 2.0−300 K. A very weak antiferromagnetic coupling between Re(IV) and Mn(II) occurs in 1 (J = −0.1 cm-1), whereas a significant ferromagnetic interaction between Re(IV) and M(II) is observed in 2−4 [J = +2.8 (2), +5.2 (3), and +5.9 cm-1 (4)].