Two-Coordinate, Late First-Row Transition Metal Amido Derivatives of the Bulky Ligand -N(SiPrⁱ₃)Dipp (Dipp = 2,6-diisopropylphenyl): Effects of the Ligand on the Stability of Two-Coordinate Copper(II) Complexes

The synthesis and spectroscopic, structural, and magnetic characterization of the quasi-linear metal­(II) bis­(amides) M­{N­(SiPrⁱ₃)­Dipp}₂ [Dipp = C₆H₃-2,6-Prⁱ₃; M = Fe (1), Co (2), or Zn (3)] are described. The magnetic data demonstrate the impact of metal ligand π-interactions on the magnetic properties of these two-coordinate transition metal amides. Disproportionation of the copper­(I) amide species featuring the ligand -N­(SiPrⁱ₃)­Dipp resulted in the decomposition product [(Prⁱ₃Si)­N­(c-C₆H₂-2,6-Prⁱ₂)]₂ (4). The electron paramagnetic resonance spectrum of the unstable two-coordinate Cu­{N­(SiPrⁱ₃)­Dipp}₂ displays significantly less Cu–N bond covalency than the stable two-coordinate copper­(II) species Cu­{N­(SiMe₃)­Dipp}₂. The testing of -N­(SiPrⁱ₃)­Dipp and a range of other, related bulky amide ligands with their copper derivatives highlights the peculiar combination of steric and electronic properties of the Wigley ligand -N­(SiMe₃)­Dipp that enable it to stabilize the unique two-coordinate copper­(II) complex Cu­{N­(SiMe₃)­Dipp}₂.