SINGLE Mo_(n)Fe_(4-n)S_(4) (n=0, 1, 2) CUBANE-LIKE CLUSTERS: PREPARATION FROM COMBI-NATION OF DINUCLEAR COMPLEXES AND THE STRUCTUREOF [Mo_(2)Fe_(2)S_(4)(C_(4)H_(8)dtc)_(6)]·3.5C_(2)H_(2)Cl_(4)