We report the formation and N-2 reactivity of novel cobalt hydride complexes supported by bulky beta-diketiminate ligands (L). Addition of KHBEt3 to LCoCl gives [LCo(mu-H)](2) (1) or K-2[LCoH](2) (2), depending on the amount of borohydride used. Compound 2 is the first example of a crystallographically characterized hydride complex in which a transition metal is three-coordinate. Both 1 and 2 react with N-2 at room temperature to give dinuclear N-2 complexes with loss of H-2.