Incorporation of the tridentate phosphine-enamidoiminophosphorane onto cobalt(II) produces tetrahedral Co(NpNP iPr )Cl, 1, which upon reduction under dinitrogen generates the T-shaped, paramagnetic Co(I) complex Co(NpNP iPr ), 2. This paramagnetic Tshaped derivative is in equilibrium with the paramagnetic dinitrogen derivative Co(NpNP iPr )-(N 2 ), 3, which can be detected by IR and low-temperature UV−vis spectroscopy. Both 1 and 2 act as homogeneous catalysts for the conversion of molecular nitrogen into tris(trimethylsilyl)amine (N(SiMe 3 ) 3 ) (∼200 equiv, quantified as NH 4 Cl after hydrolysis) in the presence of excess KC 8 and Me 3 SiCl at low temperatures.