SYNTHESES AND CHARACTERIZATION OF CUBANE-TYPE CLUSTERS WITH MOLYBDENUM-IRON-SULFUR (MO3FES4) OR MOLYBDENUM-NICKEL-SULFUR (MO3NIS4) CORES - X-RAY STRUCTURES OF [MO3FES4(H2O)(10)](CH3C6H4SO3)(4)CENTER-DOT-7H(2)OAND [MO3FES4(H2O)(NH3)(9)]CL-4, AND DISCRETE VARIATIONAL (DV)-X-ALPHACALCULATION OF THE ELECTRONIC-STRUCTURES OF [MO3FES4(H2O)(10)](4+), [MO3FES4(H2O)(NH3)(9)](4+), AND [MO3NIS4(H2O)(10)](4+)

Reaction of the incomplete cubane-type cluster [Mo3S4(H2O)(9)](4+) (A) With iron gives a novel cubane-type aqua cluster [Mo3FeS4(H2O)(10)](C H3C6H4SO'(3))(4) . 7H(2)O (B'). An ammonia coordinated derivative clus ter [Mo3FeS4(H2O)(NH3)9]Cl-4 (C') is also synthesized. X-ray structura l analyses of B' and C' revealed that the clusters, [Mo3FeS4(H2O)(10)] (4+) (B) and [Mo3FeS4(H2O)(NH3)(9)](4+) (C), have an approximate symme try of C-3 upsilon. The iron atom has fairly regular tetrahedral geome try in both clusters. The effective magnetic moments of B' at 2.16 K a nd 269.95 K are 2.78 and 3.26 B,M., respectively. Fe-57-Mossbauer spec troscopy showed that the oxidation states of iron in B' and C' were as signable to be +2.39 and +2.54, respectively, which indicates that the reaction is a reductive addition of an iron atom to the Mo3S4 core in A. The cyclic voltammograms of A, B, and [Mo3NiS4(H2O)(10)](4+) (D) s how three consecutive one electron reductive steps, respectively, and the oxidation states of metals in B and D are assigned as (MoMo2MnII)- Mo-IV-Mn-III (M=Fe, Ni). Discrete variational (DV)-X alpha calculation of B, C, and D explains the magnetic behavior, XPS spectra, and react ivity toward CO, C2H2, and C2H4.