Synthese und Strukturen der ersten mehrkernigen Mangan‐Guanidin‐Komplexe und der ersten Mangan‐Komplexe mit mono‐protonierten Bis‐Guanidinliganden

Abstract

AbstractSyntheses and Structures of the First Polynuclear Manganese Guanidine Complexes and of the First Manganese Complexes Containing Mono‐Protonated Bis‐Guanidine LigandsMetallation of two differently alkylated bis‐guanidine ligands containing a central pyridine functionality, namely N2,N6‐bis(1,3‐dimethylimidazolidin‐2‐ylidene)pyridine‐2,6‐diamine (DMEG2py {N7C15H23}, L1) and N2,N6‐bis(1,1,3,3‐tetramethyl‐guanidine)pyridine‐2,6‐diamine (TMG2py {N7C15H27}, L2), with manganese(II) bromide and chloride leads to the formation of the novel complexes [MnBr3(TMG2pyH)] ([MnBr3(N7C15H28)], (1)), [MnBr2(DMEG2pyH)2]2+ ([MnBr2(N7C15H24)2]2+, (2)), and [Mn2X3(DMEG2py)2]+ ([Mn2X3(N7C15H23)2]+; (3a): X = Cl; (3b): X = Br). 2 and 3 have been isolated as tetrahalomanganate salts. Single crystal X‐ray analyses show that all of them contain the manganese atoms in unusual pseudo‐tetrahedral coordination environments. 3a·1/2[MnCl4] and 3b·1/2[MnBr4] are isostructural and crystallize in the monoclinic space group C2c. The complex cations 3 exhibit a binuclear structure with two terminal and one bridging halide ion, respectively. The compounds 1 and 2 are mononuclear species crystallizing in the orthorhombic space group P212121 in the case of 1 and in the triclinic space group $P{\bar 1}$ in the case of 2·[MnBr4]. The ability of L1 and L2 to bind either two manganese ions naked or only one of them in the mono‐protonated stage is the most remarkable property of these ligands. Further striking features are the spatial arrangements of the pyridine‐to‐manganese bonds which deviate significantly from the situation expected for nitrogen donor functions in sp2 hybridized stages. Moreover, regarding each chelating ligand portion as a component which occupies one coordination site of the metal atom, a pseudo‐tetrahedral metal coordination is identified. To our knowledge, 1 and 2 are the first manganese complexes containing mono‐protonated bis‐guanidine ligands, whereas 3a and 3b are the first polynuclear manganese‐guanidine compounds known so far.