Compounds with symmetrical tricobalt chains wrapped by dipyridylamide ligands and cyanide or isothiocyanate ions as terminal ligands

Three new linear compounds of the type Co₃(dpa)₄X₂, where dpa is the anion of di(2-pyridyl)amine and X is NCS^- (5), CN^- (6), and N(CN)₂^- (7), have been prepared, and their structures and magnetic behavior have been studied. In all of them, including three different solvates of 5, the Co₃ chains are symmetrical with Co-Co distances of ca. 2.31-2.32 Å. The appearance of four lines in the ¹H NMR spectra of the three compounds is also consistent with a symmetrical structure in solution. For all compounds, the magnetic behavior is quite similar with μ_eff of ca. 1.9-2.0 μ_B at temperatures between 1.8 and 200 K. As the temperature increases, the effective moments increase gradually, but since saturation is not reached, even at 400 K, the high-spin state cannot be assigned.