Linear tricobalt compounds with di-(2-pyridyl)amide (dpa) ligands:: Studies of the paramagnetic compound Co3(dpa)4Cl2 in solution

Solutions of Co-3(dpa)(4)Cl-2, where dpa = di(2-pyridyl)amide ion, in CD2Cl2 were studied by NMR in the temperature range 183-303 K. The spectra show only four H-1 and five C-13 resonance signals, consistent with the D-4 symmetry of the molecules found in the solid. The magnetic susceptibility in solution was determined by the Evans method from 193 to 308 K. These observations can be modeled as an S = 1/2 to S = 5/2 spin-transition process with Delta H = 7.7(2) kJ mol(-1) and Delta S = 20.8(8) J K-1 mol(-1).