Multimetallic cooperativity is believed to play a key role in the cleavage of dinitrogen to nitrides (N), but the mechanism remains ambiguous due to the lack of isolated intermediates. Herein, we report the reduction of the complex [K{U(OSi(OBu))(μ-η:η-N)}], , with KC, yielding the tetranuclear tetranitride cluster [K{(OSi(OBu))U}{(OSi(OBu))U}(μ-N)(μ-N)(μ-O)], , a novel example of N cleavage to nitride by a diuranium complex. The structure of complex is remarkable, as it contains a unique uranium center bound by four nitrides and provides the second example of a -N═U═N core analogue of UO. Experimental and computational studies indicate that the formation of the U(IV)/U(VI) tetrauranium cluster occurs via successive one-electron transfers from potassium to the bound N ligand in complex , resulting in N cleavage and the formation of the putative diuranium(V) bis-nitride [K{U(OSi(OBu))(μ-N)}], . Additionally, cooperative potassium binding to the U-bound N ligand facilitates dinitrogen cleavage during electron transfer. The nucleophilic nitrides in both complexes are easily functionalized by protons to yield ammonia in 93-97% yield and with excess CO to yield KCN and KNCO. The structures of two tetranuclear U(IV)/U(V) bis- and mononitride clusters isolated from the reaction with CO demonstrate that the nitride moieties are replaced by oxides without disrupting the tetranuclear structure, but ultimately leading to valence redistribution.