X-ray structure and spectroscopic characterization of divalent dinuclear cobalt complexes containing carboxylate- and phosphodiester- auxiliary bridges

Two dinuclear spin-coupled divalent cobalt complexes, [Co2(P1-O−)(μ2-OAc−)](ClO4)2, (1) and [Co2 (P1-O−)(μ2-BNPP−)](ClO4)2, (2) containing μ-1,3 acetate (OAc−) and bis(4-nitrophenyl)phosphate (BNPP−) auxiliary bridges, respectively, were synthesized. They were characterized by single crystal X-ray diffraction, to show a trigonal bipyramidal geometry around each cobalt center and the intervening bridging atoms that are responsible for spin-transfer between the two divalent cobalt centers; the alkoxo oxygen donor occupies an equatorial position, and the auxiliary ligand oxygens (OAc−/BNPP−) occupy the axial positions. Solution state magnetic moment measurement together with UV-Vis/NIR spectra revealed a high-spin ground state (S = 3/2) for Co(II) in these compounds. Complexes 1 and 2 show interesting 1H NMR spectral features of resonances with relatively narrower linewidths in conjunction with a sizable chemical shift dispersion of −5 and 265 ppm.