Tetranuclear manganese (III) salicylaldoxime ensemble

Abstract

Crystal structure of {[Mn(salicylaldoximeH) (salicylaldoxime)] 4 } Á 3CHCl 3 1 formed by the interaction of MnCl 2 Á 4H 2 O and salicylaldoxime in a 1:1 ratio is described. The compound crystallizes in the orthorhombic space group Pbca (No 61) with the lattice parameters; a = 27.769 (3), b = 22.672 (2), c = 21.650 (2) Å , V = 13630 (2) Å 3 , Z = 8, R 1 = 0.0776, wR 2 = 0.2356, S = 1.164. The cluster with four Mn (III) centers formed by four terminal and four bridging salicylaldoxime ligands results in a central rotating wheel-like core with the Mn-Mn separation varying from 3.531 to 3.576 Å and with the diagonal distances being 4.156-4.165 Å . Four intramolecular H-bonds between a terminal oxime (NOH) group and the adjacent phenolate oxygen atom of another ligand stabilize the structure of the cluster. Spectral, magnetic, and cyclic voltammetry studies corroborate a stable Mn (III) tetramer.

Synthesis and Properties of Complexes with Unusual {MnIII4} and {MnII4} Cages

“…For 1a , the effective magnetic momentum per formula unit decreases from 11.1 μ B at 300 K to 5.1 μ B at 5 K (Figure S5), similar to the values reported by Kumbhar et al (10.45 μ B at 238.5 K, 7.39 μ B at 5 K4). Curie–Weiss fits of the data in the temperature range from 50 K to 300 K reveal a magnetic momentum of 5.8 μ B and a Weiss temperature of –16 K, which remains to be explained in future studies.…”

“…The molecular structures of 1a and 1b (Figure 2, top) are analogous to the reported one,4 with four Mn III atoms linked by four fully deprotonated and four monoprotonated salicylaldoxime ligands. A characteristic “rotating wheel‐like” arrangement is observed, with salicylaldoxime ligands linked by O–H ··· O hydrogen bonds.…”

“…In the unusual {Mn III 4 } cage, four Mn III atoms are linked through N–O oxime groups of the oxime ligand. The second known example of a compound with this core is a tetranuclear manganese(III) salicylaldoxime ensemble reported by Kumbhar et al, [Mn 4 (sao) 4 (saoH) 4 ]·3CHCl 3 ( B ) 4. In contrast to A , compound B exhibits antiferromagnetic behavior with weakly coupled Mn 3+ atoms, which has been, however, not discussed so far.…”

Manganese–Salicyloximate Clusters Starting from [MnII(hfacac)2]: From Mn4 to Mn12

“…The molecular structure of the tetranuclear complex 2 is shown in Figure 3 and selected bond parameters are reported in Table 3. The structure of this compound is a polymorph of the 2a· 3.5MeCN complex reported by Brechin and co‐workers8a,8c and is closely related to the chloroform‐ or methanol‐solvated clusters bearing the salicylaldoximato ligand 8b,8d. The structure consists of four Mn III cations that form a pseudo‐cubane cage in which each pentagonal face is defined by one Mn–N–O–Mn and one Mn–O–Mn linkage.…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 19, 2008) and the discipline

“…In the following paper, Kumbhar et al [250] presented the crystal structure of {[Mn(salicylaldoximeH) (salicylaldoxime)] 4 }Á3CHCl 3 . The complex contains four Mn(III) clusters with four terminal and four bridging salicylaldoxime (four monoanionic and four dianionic) ligands and is stabilized by four intramolecular hydrogen bonds between the terminal oxime group and the adjacent phenolate oxygen atom of another ligand.…”