Synthesis, spectroscopic studies and magnetic properties of binuclear complexes of the first transition series cations bridged by 2,2 '-bipyrimidine

Binuclear complexes [M2Cl4(mu-bpym)], where M = VO2+, Fe-II, Co-II or Cu-II and bpym = 2,2'-bipyrimidine, and [M-2(hfacac)(4)(mu-bpym)] complexes, whe re hfacac = hexafluoroacetylacetonate and M = Fe-II, Ni-II or Co-II have be en synthesized and characterized by chemical analysis, conductance measurem ents, i.r., electronic and e.p.r spectroscopies and by magnetic susceptibil ity measurements (in the 4.2-291 K range). Co-II and Fe-II are in a high sp in state. [(VO)(2)Cl-4(mu-bpym)] is paramagnetic, without significant inter actions. [Fe2Cl4 (mu-bpym)] shows a singular behaviour explained by an anti ferromagnetic intradimer exchange and a ferromagnetic interdimer interactio n. All other complexes are antiferromagnetic, with an intramolecular exchan ge parameter, J, varying from -3.3 cm(-1) for Co-II to -109 cm(-1) for Cu-I I.