A mechanistic pathway for the formation of the structurally characterized manganese-amide-hydrazide pinned butterfly complex, Mn-4(mu 3-PhN-NPh-kappa N-3,N')(2)(mu-PhN-NPh-kappa(2)-N,N')(mu-NHPh)(2)L-4 (L = THF, py), is proposed and supported by the use of labeling studies, kinetic measurements, kinetic competition experiments, kinetic isotope effects, and hydrogen atom transfer reagent substitution, and via the isolation and characterization of intermediates using X-ray diffraction and electron paramagnetic resonance spectroscopy. The data support a formation mechanism whereby bis[bis(trimethylsilyl)amido]manganese(II) (Mn(NR2)(2), where R = SiMe3) reacts with N,N'-diphenylhydrazine (PhNHNHPh) via initial proton transfer, followed by reductive NN bond cleavage to form a long-lived Mn-IV imido multinuclear complex. Coordinating solvents activate this cluster for abstraction of hydrogen atoms from an additional equivalent of PhNHNHPh resulting in a Mn(II)phenylamido dimer, Mn-2(mu-NHPh)(2)(NR2)(2)L-2. This dimeric complex further assembles in fast steps with two additional equivalents of PhNHNHPh replacing the terminal silylamido ligands with kappa(1)-hydrazine ligands to give a dimeric Mn-2(mu-NHPh)(2)(PhN-NHPh)(2)L-4 intermediate, and finally, the addition of two additional equivalents of Mn(NR2)(2) and PhNHNHPh gives the pinned butterfly cluster.