The synthesis of new dinuclear manganese(IV) complexes possessing the [Mn-2(IV)(mu-O)(2)(mu-O2CMe)](3+) core and containing halide ions as terminal ligands is reported. [Mn2O2(O2CMe)Cl-2(bpy)(2)](2)[MnCl4] (1; bpy = 2,2'-bipyridine) was prepared by sequential addition of [MnCl3(bpy)(H2O)] and (NBzEt(3))(2)[MnCl4] to a CH2Cl2 solution of [Mn3O4-(O2CMe)(4)(bPY)(2)]. The complex [(Mn2O2)-O-IV(O2CMe)Cl(bpy)(2)(H2O)](NO3)(2) (2) was obtained from a water/acetic acid solution of MnCl2.4H(2)O, bpy, and (NH4)(2)[Ce(NO3)(6)], whereas the [(Mn2O2)-O-IV(O2CR)X(bPY)(2)(H2O)](ClO4)(2) [X = Cl- and R = Me (3), Et (5), or C2H4Cl (6); and X = F-, R = Me (4)] were prepared by a slightly modified procedure that includes the addition of HClO4. For the preparation of 4, MnF2 was employed instead of MnCl2.4H(2)O. [Mn2O2(O-2-CMe)Cl-2(bpy)(2)](2)[MnCl4].2CH(2)Cl(2) (1.2CH(2)Cl(2)) crystallizes in the monoclinic space group C2/c with a = 21.756(2) Angstrom, b = 12.0587(7) Angstrom, c = 26.192(2) Angstrom, alpha = 90degrees, beta = 111.443(2)degrees, gamma = 90degrees, V = 6395.8(6) Angstrom(3), and Z = 4. [Mn2O2(O2CMe)Cl(H2O)(bPY)(2)](NO3)(2).H2O (2.H2O) crystallizes in the triclinic space group P1 with a = 11.907(2) Angstrom, b = 12.376(2) Angstrom, c = 10.986(2) Angstrom, alpha = 108.24(1)degrees, beta = 105.85(2)degrees, gamma = 106.57(1)degrees, V = 1351.98(2) Angstrom(3), and Z = 2. [Mn2O2(O2CMe)Cl(H2O)(bpy)(2)](ClO4)(2).MeCN (3.MeCN) crystallizes in the triclinic space group P1 with a = 11.7817(7) Angstrom, b = 12.2400(7) Angstrom, c = 13.1672(7) Angstrom, alpha = 65.537(2)degrees, beta = 67.407(2)degrees, gamma = 88.638(2)degrees, V =1574.9(2)Angstrom(3), and Z = 2. The cyclic voltammogram (CV) of 1 exhibits two processes, an irreversible oxidation of the [MnCl4](2-) at E-1/2 similar to 0.69 V vs ferrocene and a reversible reduction at E-1/2 = 0.30 V assigned to the [Mn2O2(O2CMe)Cl-2(bpy)(2)](+/0) couple (2Mn(IV) to (MnMnIII)-Mn-IV). In contrast, the CVs of 2 and 3 show only irreversible reduction features. Solid-state magnetic susceptibility (chi(M)) data were collected for complexes 1.1.5H(2)O, 2.H2O, and 3.H2O in the temperature range 2.00-300 K. The resulting data were fit to the theoretical chi(M)T vs Texpression for a Mn-2(IV) complex derived by use of the isotropic Heisenberg spin Hamiltonian (H = -2J (S) over cap (1)(S) over cap (2)) and the Van Vleck equation. The obtained fit parameters were (in the format J/g) -45.0(4) cm(-1)/2.00(2), -36.6(4) cm(-1)/1.97(1), and -39.3(4) cm(-1)/1.92(1), respectively, where J is the exchange interaction parameter between the two Mn-IV ions. Thus, all three complexes are antiferromagnetically coupled.