The structural and magnetic properties of dinuclear [Co-II(NCMe)(5)Co-II(NCS)(4)] center dot MeCN have been investigated. The structure consists of an octahedral Coil(NCMe); center connected to a tetrahedral Coll(NCS)4 center bridged by mu(1,3)-NCS- ligand. The bridging NCS- weakly couples the pair of S = 3/2 Co-II spin sites, as evidenced by the magnetic data being best fit by the Curie-Weiss expression with theta = -15.5 K.