The pentanuclear compound [V-II(tmphen)(2)](3)[Mo-III(CN)(6)](2) (tmphen = 3,4,7,8-tetra-methyl-1,10-phenanthroline) exhibits a record antiferro-magnetic exchange coupling constant of J(V)-M-o = -114 cm(-1). This is the first example of a heterobimetallic cyanide compound with such strong magnetic coupling.