Facile access to redox-active C2-bridged complexes with half-sandwich manganese end groups

The dinuclear mixed-valent complex (MeC5H4)(dmpe)MnC(2)Mn(dmpe)(C5H4Me)](+)(eta2-MeC5H4)3Mn](-)1](+)2]- (dmpe=1,2-bis(dimethylphosphanyl)ethane) was prepared by the reaction of Mn(MeC5H4)2] with dmpe and Me(3)SnCtriple chemical bond]CSnMe3. The reactions of 1](+)2]- with KPF6] and NaBPh4] yielded the corresponding anion metathesis products (MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)]PF6] (1]PF6]) and (MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)]BPh4] (1]BPh4]). These mixed-valent species can be reduced to the neutral form by reaction with Na/Hg. The obtained complex (MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)] (1) displays a triplet/singlet spin equilibrium in solution and in the solid state, which was additionally studied by DFT calculations. The diamagnetic dicationic species (MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)]PF6]2 (1]PF6]2) was obtained by oxidizing the mixed-valent complex 1]PF6] with one equivalent of Fe(C5H5)2]PF6]. Both redox processes are fully reversible. The dinuclear compounds were characterized by NMR, IR, UV-visible, and Raman spectroscopy, cyclic voltammetry, and magnetic susceptibility measurements. X-ray diffraction studies were performed on 1]2], 1]PF6], 1]BPh4], and 1]PF6]2.