Ferrocene–MnII π-interaction in the complex [Fc2BpzPh2Mn(THF)Cl]

The ferrocene-based bis(pyrazol-1-yl)borate ligands [Fc2Bpz2]− ([2]−) and [Fc2BpzPh2]− ([2Ph]−) have been prepared (Fc: ferrocenyl; pz: pyrazol-1-yl; pzPh: 3-phenylpyrazol-1-yl). Treatment of [2]− and [2Ph]− with MnCl2 in THF leads to the complexes [Fc2Bpz2Mn(THF)(μ-Cl)2Mn(THF)pz2BFc2] (3) and [Fc2BpzPh2Mn(THF)Cl] (3Ph), respectively, which have been structurally characterized by X-ray crystallography. While there is clearly no ferrocene–MnII π-coordination in the solid-state structure of 3, short MnII–C5H4 contacts are established in 3Ph (shortest Mn–C distances: 2.780(2) Å, 2.872(2) Å). The cyclic voltammograms of K[2Ph] and 3Ph show the first ferrocene/ferricinium redox wave of 3Ph to be shifted anodically by 0.60 V compared with the first FeII/FeIII transition of K[2Ph].

Graphical abstractTwo short Mn–C contacts between the MnII-ion and the ferrocene cyclopentadienyl ring have been observed in the complex [Fc2BpzPh2Mn(THF)Cl] indicating multiple-decker sandwich character of the (C5H5)Fe(C5H4R)Mn fragment (R = BpzPh2Fc).Figure optionsDownload full-size imageDownload as PowerPoint slide