Two-Coordinate, Late First-Row Transition Metal Amido Derivatives of the Bulky Ligand-N(SiPr3i)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(SiPr3i)Dipp}(2) [Dipp = C6H3-2,6-Pr-3(i); M = Fe (1), Co (2), or Zn (3)] are described. The magnetic data demonstrate the impact of metal ligarid pi-interactions on the magnetic properties of these two-coordinate transition metal amides. Disproportionation of the copper(I) amide species featuring the ligand -N(SiPr3i)Dipp resulted in the decomposition product [((Pr3Si)-Si-i)N(c-C6H2-2,6-Pr-2(i))](2) (4). The electron paramagnetic resonance spectrum of the unstable two-coordinate Cu{N(SiPr3i)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(SiPr3i)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).