Dispersion force stabilized two-coordinate transition metal-amido complexes of the -N(SiMe3)Dipp (Dipp = C6H3-2,6-Pr i2) ligand: Structural, spectroscopic, magnetic, and computational studies

Article abstract of DOI:10.1021/ic402105m

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(SiMe₂CH ₂)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.