The reactivity of the recently reported 3H-1,2,4-diazaphosphole 1 toward electron-rich Ni and Co complexes is described. Compound 1 reacts with [Ni(cod)2] (cod = 1,5-cyclooctadiene) to afford complex 2, which features a 1,2,3-triazole-4-ylidene-type carbene ligand derived from the cleavage of the C―C(Ph) bond in 1. In contrast, [(IPr)Ni(vtms)2] induces N―C(iPr) bond cleavage of the 1,2,3-triazole part of 1 (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; vtms = H2C=CH(SiMe3)). The resulting Ni(II) complex 3 additionally features a CH2CH2SiMe3 ligand, resulting from a formal H atom transfer to a vtms ligand. Analogous N―C(iPr) bond activations are observed in the reactions of 1 toward [(NHC)Co(vtms)2] (NHC = IPr or IMes; IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene). However, no H atom transfer is observed in this case, and one vtms ligand is retained in the resulting Co(I) complexes 4 and 5. The Ni(II) complexes 2 and 3 have square planar molecular structures and are diamagnetic, whereas the Co(I) centers in 4 and 5 exhibit tetrahedral coordination environments, leading to paramagnetic behavior.