Alkali metal reductions of M(CO)4(TMED), TMED = N,N,N′,N′-tetramethylethylenediamine, in liquid ammonia provide high yields of the “super-reduced” species Na4M(CO)4 which contain chromium, molybdenum, and tungsten in their lowest known formal Oxidation states. These substances have been isolated as somewhat shock-sensitive yellow to orange solids which give acceptable elemental analyses for the proposed formulations. Treatment of liquid ammonia slurries of Na4M(CO)4 with 4 equiv of NH4C1 produces good yields (50-80%) of the corresponding M(CO)4(NH3)2, while 2.5 equiv of NH4Cl or excess acetonitrile gives 20-50% yields of H2M2(CO)8 2- which have been isolated as Et4N+ or (Ph3P)2N+ salts. The chromium and molybdenum dianions are new species and are characterized by their elemental compositions and infrared and 1H NMR spectra. The first well-defined reactions of H2W2(CO)8 2- with nucleophiles are reported. New Compounds formed in these reactions are [Et4N]2[W2(CO)8(PMe3)2], [Et4N]2[W2(CO)8(PMe2Ph)2], [Et4N]2[W2(CO)8(P(OMe)3)2], and K2H2W(CO)4. The former are the first reported bisphosphine-substituted derivatives of M2(CO)10 2- dianions, while H2W(CO)4 2- is formally a diprotonated derivative of W(CO)4 4-. High yields (70%) of H2W(CO)4 2- are also obtained by the reaction of W(CO)4(TMED) with excess K[sec-Bu3BH] in THF. Treatment of W2(CO)8L2 2- with water provides the hydride anions, HW2(CO)8L2-, which are isolated as Et4N+ salts and characterized by elemental analyses and infrared and 1H NMR spectra.