Two-Coordinate, Late First-Row Transition Metal Amido Derivatives of the Bulky Ligand -N(SiPr i 3)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(SiPr i 3)­Dipp}2 [Dipp = C6H3-2,6-Pr i 3; 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(SiPr i 3)­Dipp resulted in the decomposition product [(Pr i 3Si)­N­(c-C6H2-2,6-Pr i 2)]2 (4). The electron paramagnetic resonance spectrum of the unstable two-coordinate Cu­{N­(SiPr i 3)­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(SiPr i 3)­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.