The reaction of equimolar trimethylsilyldiazomethyllithium (LiTMSD) with high spin (S = 2) PhB(AdIm) 3 FeCl (PhB(AdIm) 3 − = tris(3-adamantylimidazol-2-ylidene)phenylborate) affords the corresponding N-nitrilimido complex PhB(AdIm) 3 Fe−N�N�C(SiMe 3 ). This complex can be converted to the thermodynamically more favorable C-isocyanoamido isomer PhB(AdIm) 3 Fe−C�N�N(SiMe 3 ) by reaction with an additional equivalent of LiTMSD. While the iron(II) complexes are four-coordinate, the diazomethane is bound side-on in the iron(I) congener PhB(AdIm) 3 Fe(N,N′-κ 2 -N 2 C(H)Si(CH 3 ) 3 ). The latter complex adopts high spin (S = 3/2) ground state and features an unusually weak C−H bond. Photolysis of the iron(II) complexes induces N�N bond cleavage, with the iron(II) cyanide PhB(AdIm) 3 Fe−C�N and iron(IV) nitride PhB(AdIm) 3 Fe�N complexes being the major products of the reaction. The same products are obtained when the iron(I) complex is photolyzed or treated with a fluoride source. The trimethylsilyldiazomethane-derived ligand disassembly reactions are contrasted with those observed for related tris(carbene)amine complexes.