Borohydride, Azide, and Chloride Anions As Terminal Ligands on Fe/Mo/S Clusters. Synthesis, Structure and Characterization of [(Cl\\r sub/4sub\\r -cat)(PPr\\r sub/3sub\\r ) MoFe\\r sub/3sub\\r S\\r sub/4sub\\r (X)\\r sub/2sub\\r ]\\r sub/2sub\\r (Bu\\r sub/4sub\\r N)\\r sub/4sub\\r and [(Cl\\r sub/4sub\\r -cat)(PPr\\r sub/3sub\\r )MoFe\\r sub/3sub\\r S\\r sub/4sub\\r (PPr\\r sub/3sub\\r )(X)]\\r sub/2sub\\r (Bu\\r sub/4sub\\r N)\\r sub/2sub\\r (X = N\\r sub/3subsup-sup\\r , BH\\r sub/4subsup-sup\\r , Cl\\r sup-sup\\r ) Double-Fused Cubanes. NMR Reactivity Studies of [(Cl\\r sub/4sub\\r -cat)(PPr\\r sub/3sub\\r ) MoFe\\r sub/3sub\\r S\\r sub/4sub\\r (BH\\r sub/4sub\\r )\\r sub/2sub\\r ]\\r sub/2sub\\r (Bu\\r sub/4sub\\r N)\\r sub/4sub