Trimethylsilyldiazomethane Disassembly at a Three-Fold Symmetric Iron Site

The reaction of equimolar trimethylsilyldiazomethyllithium (LiTMSD) with high spin (S = 2) PhB­(AdIm)3FeCl (PhB­(AdIm)3– = tris­(3-adamantylimidazol-2-ylidene)­phenylborate) affords the corresponding N-nitrilimido complex PhB­(AdIm)3Fe–NNC­(SiMe3). This complex can be converted to the thermodynamically more favorable C-isocyanoamido isomer PhB­(AdIm)3Fe–CNN­(SiMe3) 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)3Fe­(N,N′-κ2-N2C­(H)­Si­(CH3)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)3Fe–CN and iron­(IV) nitride PhB­(AdIm)3Fe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.