A hexanuclear cyano-bridged {(Mn4Nb2IV)-Nb-II} Cluster (1) bearing 2,2 '-bipyridine (bpy) as the blocking ligand at manganese is obtained from the reaction of cis-[MnCl2(bpy)(2)] and K-4[Nb(CN)(8)]. When the blocking ligand is 1,10-phenanthroline (phen), a nonanuclear cluster {(Mn6Nb3IV)-Nb-II} (2) is obtained. The structure of [{Mn(bpy)(2)}(4){Nb(CN)(8)}(2)] has been solved by single-crystal X-ray crystallography, whereas the phen derivative has been confirmed by means of the structure analysis of the corresponding W-IV analogue [{Mn(phen)(2)}(6){W(CN)(8)}(3)(H2O)(2)]. Magnetic measurements revealed S = 9 and 21/2 spin ground states for these aggregates as a result of antiferromagnetic Nb-Mn interaction with J(Nb-Mn) = -18.1 cm(-1) (1) and -13.6 cm(-1) (2).