Cyanide-limited complexation of molybdenum(III):: Synthesis of octahedral [Mo(CN)6]3- and cyano-bridged [Mo2(CN)11]5-

Octahedral coordination of molybdenum(III) is achieved by limiting the amount of cyanide available upon complex formation. Reaction of Mo(CF3SO3)3 with LiCN in DMF affords Li3[Mo(CN)6]·6DMF (1), featuring the previously unknown octahedral complex [Mo(CN)6]3-. The complex exhibits a room-temperature moment of μeff = 3.80 μB, and assignment of its absorption bands leads to the ligand field parameters Δo = 24800 cm-1 and B = 247 cm-1. Further restricting the available cyanide in a reaction between Mo(CF3SO3)3 and (Et4N)CN in DMF, followed by recrystallization from DMF/MeOH, yields (Et4N)5[Mo2(CN)11]·2DMF·2MeOH (2). The dinuclear [Mo2(CN)11]5- complex featured therein contains two octahedrally coordinated MoIII centers spanned by a bridging cyanide ligand. A fit to the magnetic susceptibility data for 2, gives J = -113 cm-1 and g = 2.33, representing the strongest antiferromagnetic coupling yet observed through a cyanide bridge. Efforts to incorporate these new complexes in magnetic Prussian blue-type solids are ongoing. Copyright © 2002 American Chemical Society.