Symmetric and Asymmetric Dinuclear Manganese(IV) Complexes Possessing a [(Mn)^IV2((mu)-O)2((mu)-(O)2CMe)]^(3+) Core and Terminal (Cl)- Ligands

The synthesis of new dinuclear manganese(IV) complexes possessing the [(Mn)2(-0)2-C)2CMe)] core and containing halide ions as terminal ligands is reported. [(Mn)2(0)2((0)2CMe)(Cl)2(bpy)2]2[Mn(Cl)4] (1; bpy = 2,2ʹ-bipyridine) was prepared by sequential addition of [MnCls(bpy)((H)20)] and (NBzEts)2[Mn(Cl)4] to a 012012 solution of [1304(C)2CMe)4(bpy)2]. The complex [(Mn)2(0)2((0)2CMe)CI(bpy)2((H)20)](N(0)3)2 (2) was obtained from a water/acetic acid solution of Mn(Cl)2-4(H)20, bpy, and (NhNC], whereas the [Mn(0)2((0)2CR)X(bpy)2((H)20)3(C1(0)4)2 [X - Gland R= Me (3), Et (5), or 241 (6); and X = F-, R = Me (4)] were prepared by a slightly modified procedure that includes the addition of HCIC)4. For the preparation of 4, Mn(F)2 was employed instead of MnCIO. 2(0)2((0)2CMe)(Cl)2(bpy)2]2[Mn(Cl)4]-2C(H)2(Cl)2 (1-2(0)12(0)12) crystallizes in the monoclinic space group (C)2/c with a = 21.756(2) A, b = 12.0587(7) A, c = 26.192(2) A, a = 90°, (beta) = 111.443(2)°, y = 90°, V = 6395.8(6) A and Z-4. [(Mn)2(0)2((0)2CMe)CI((H)20)(bpy)2](N(0)3)2-(H)20 (220) crystallizes in the triclinic space group PI with a = 11.907(2) A, b = 12.376(2) A, c = 10.986(2) A, a = 108.24(1)°, (beta) = 105.85(2)°, y - 106.57(1)°, V= 1351.98(2) A and Z= 2. [(Mn)2(0)2(C)2CMe)CI((H)20)(bpy)2](C1(0)4)2-MeCN (3-MeCN) crystallizes in the triclinic space group PI with a = 11.7817(7) A, b = 12.2400(7) A, c = 13.1672(7) A, a = 65.537(2)°, (beta) = 67.407(2)°, y - 88.638(2)°, V 1574.9(2) A and Z= 2. The cyclic voltammogram (CV) of 1 exhibits two processes, an irreversible oxidation of the [MnCL at 51/2 0.69 V vs ferrocene and a reversible reduction at E1/2 = 0.30 V assigned to the [(Mn)2(0)2((0)2CMe)(Cl)2(bpy)2 couple (2Mn to Mn Mn"ʹ). In contrast, the CVs of 2 and 3 show only irreversible reduction features. Solid-state magnetic susceptibility (M) data were collected for complexes 1-1.510, 220, and 320 in the temperature range 2.00-300 K. The resulting data were fit to the theoretical ... expression for a Mn2 complex derived by use of the isotropic Heisenberg spin Hamiltonian (.T== -252) and the Van Vieck equation. The obtained fit parameters were (in the format Jig) -45.0(4) cm~V2.00(2), -36.6(4) cm-Vl.97(1), and -39.3(4) cmʹVl.92(1), respectively, where J is the exchange interaction parameter between the two Mn ions. Thus, all three complexes are antiferromagnetically coupled.