Dispersion Force Stabilized Two-Coordinate Transition Metal–Amido Complexes of the −N(SiMe3)Dipp (Dipp = C6H3-2,6-Pri2) Ligand: Structural, Spectroscopic, Magnetic, and Computational Studies

A series of high spin, two-coordinate first row transition metal–amido complexes, M{N(SiMe3)Dipp}2 {M = Fe (1), Co (2), or Ni (3); Dipp = C6H3-2,6-Pri2} and a tetranuclear C–H activated chromium amide, [Cr{N(SiMe2CH2)Dipp}2Cr]2(THF) (4), were synthesized by reaction of their respective metal dihalides with 2 equiv of the lithium amide salt. They were characterized by X-ray crystallography, electronic and infrared spectroscopy, SQUID magnetic measurements, and computational methods. Contrary to steric considerations, the structures of 1–3 display planar eclipsed M{NSiC(ipso)}2 arrays and short M–N distances. DFT calculations, corrected for dispersion effects, show that dispersion interactions involving C–H–H–C moieties likely stabilize the structures by 21.1–29.4 kcal mol–1, depending on the level of the calculations employed. SQUID measurements confirm high spin electron configurations for all the complexes and substantial orbital contributions for 1 and 2.