BINUCLEAR BIS(MU-OXO)DIMANGANESE(III,IV) AND BIS(MU-OXO)DIMANGANESE(IV,IV) COMPLEXES WITH N,N'-BIS(2-PYRIDYLMETHYL)-1,2-ETHANEDIAMINE

The magnetic susceptibility, EPR and visible spectra, and electrochemical properties of the mixed-valence complex [(bispicen)-MnO2Mn(bispicen)](ClO4)3 [bispicen = N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine, C14H18N4] are reported. The complex has a doublet ground state with J = -140 ± 1 cm−1; the EPR spectrum shows a 16-line pattern. The complex exhibits quasi-reversible waves at 191 and 798 mV (vs Ag/AgCl), corresponding to the III/III ↔ III/IV and III/IV ↔ IV/IV couples, respectively. The IV/IV complex [(bispicen)Mn02Mn(bispicen)](ClO4)4•2CH3CN has been synthesized, and its crystal structure has been determined. The complex crystallizes in the monoclinic space group C2/c with four centrosymmetric binuclear complexes in a cell of dimensions a = 12.070 (3) Å, b = 15.871 (3) Å,c = 22.016 (5) Å, and β = 97.46 (2)°. The structure has been refined to a final value of R = 0.040 based on 3078 independent intensities gathered at −100 °C. The Mn-Mn separation is 2.672 (1) Å, and the Mn-O-Mn bridging angle is 95.0 (2)°. The magnetic properties of the dimer are consistent with a singlet ground state, and J = −125.6 ± 0.2 cm−1. The electronic spectrum is in some ways similar to that of the III/IV complex, but there is no intervalence charge-transfer band. © 1990, American Chemical Society. All rights reserved.