Two complexes, [Mn 2 (etsalim) 4 (Hetsalim) 2 ](ClO 4 ) 2 (1), and [Mn(mesalim) 2 (OAc)(MeOH)]·MeOH (2), in which Hmesalim and Hetsalim are methyl and ethyl salicylimidate, respectively, have been synthesized, fully characterized by X-ray analyses, magnetic susceptibility, UV/Vis and IR spectroscopy, and their catalase activity has been studied. Complex 1 is dinuclear and shows an Mn−Mn distance of 3.37 Å while complex 2 is mononuclear. Both complexes catalyze the disproportionation of hydrogen peroxide into water and dioxygen; they show very high catalase activity exhibiting saturation kinetics in the presence of NaOH. The rate and turnover number of the catalyzed reaction increase dramatically when a few equivalents of base (NaOH) are added to the reaction mixture. The turnover numbers for hydrogen peroxide disproportionation increase from approximately 200 to more than 1500 per manganese ion in less than 2 min for both com-

A series of five new dinuclear manganese(II/II) compounds with derivatives of 2-{[bis(pyridin-2-ylmethyl)amino]-methyl}phenol (HL 1 ) were synthesized and structurally characterized. All complexes crystallize in monoclinic space groups and exhibit Mn···Mn separations in the range of 3.392(8)−3.493(2) Å caused by bis(µ-phenoxo) bridging modes. The derivatives of HL 1 contain either electron-donating or -withdrawing substituents. A correlation between the electronic character of the different ring substituents, the

The trinuclear manganese(II) complexes [Mn3(L1)2(μ‐OAc)4]·2Et2O {HL1 = (1‐hydroxy‐4‐nitrobenzyl)((2‐pyridyl)methyl)((1‐methylimidazol‐2‐yl)methyl)amine} (1·2EtOH), [Mn3(L2)2(μ‐OAc)4] {HL2 = ((1‐methylimidazol‐2‐yl)methyl)(1‐hydroxybenzyl)amine} (2) and [Mn3(L3)2(μ‐OAc)6] {L3 = bis(1‐methylimidazol‐2‐yl)methanone} (3) were synthesized. The compounds were characterized by X‐ray crystallography, mass spectrometry, IR, UV‐vis spectroscopy, and elemental analysis. The manganese atoms in 1 and 2 are bridged by phenol moieties of the ligands and acetates. In 3 they are only bridged by acetates in a mono‐ and bi‐dentate way. The resulting Mn···Mn distances are 3.233(1) Å (1), 3.364(1) Å (2) and 3.643(7) Å (3). In the present compounds different limiting cases for the phenomenon of the carboxylate shift are realized. Besides symmetric mono‐ and bi‐dentate bridging an unusual intermediate is also observed. 1·2EtOH is the first example of a trinuclear model for the OEC that shows catalase activity. Furthermore it was characterized by temperature dependent magnetic susceptibility measurements and a total spin ground state of St = 5/2 was found. The results for 1 reveals antiferromagnetic coupling between the central and the terminal manganese ions, with J = −1.2 cm−1, g = 2.00 (fixed), χTIP = 150×10−6 cm3mol−1.

Synthesis and Characterization of Novel Five‐ and Six‐coordinate Manganese Complexes as Catechol Dioxygenase Models The five‐ and six‐coordinate manganese complexes [Mn(tphhp)Cl2] {tphhp = N,N′‐bis(2‐pyridylmethyl)‐2‐(2‐pyridyl)hexahydropyrimidine} (1), [Mn(bpma)Cl](ClO4) {bpma = bis((2‐pyridylmethyl)((1‐methylbenzimidazol‐2‐yl)‐methyl)amine} (2) and [Mn(L)TCC] {HL = (1‐hydroxy‐4‐nitrobenzyl)((1‐methylimidazol‐2‐yl)methyl)(2‐pyridylmethyl)amine} (3) were synthesized and characterized by various techniques such as single crystal X‐ray structure analysis, mass spectrometry, IR and UV/vis spectroscopy, cyclic voltammetry, and elemental analysis. 1 and 2 crystallize in the monoclinic space group P21/n (No. 14) (1) and P21/c (No. 14) (2). The ligand and the chlorine ions provide the N3Cl2‐donorset in 1 and the N3Cl2‐donorset in 2, respectively. Compounds 1 and 2 show catalytic activity regarding the oxidation of 3,5‐di‐tertbutylcatechol to 3,5‐di‐tert‐butylchinon. To our knowledge, 1 and 2 are the first five‐coordinate manganese complexes that show catecholase activity. 3 crystallize in the orthorhombic space group P212121 (No. 19) and the ligand and tetrachlorocatechol (TCC) build the N3O3‐donorset in 3.