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

Three new linear compounds of the type Co-3(dpa)(4)X-2, 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 Angstrom. The appearance of four lines in the H-1 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 mu (eff) of ca. 1.9-2.0 mu (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.