Trimethylsilyldiazomethane Disassembly at a Three-Fold Symmetric Iron Site.

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.