Quasilinear 3d-metal(i) complexes [KM(N(Dipp)SiR3)2] (M = Cr–Co) – structural diversity, solution state behaviour and reactivity

Abstract

The synthesis and characterization of neutral quasilinear 3d-metal(I) complexes of chromium to cobalt of the type [KM(N(Dipp)SiMe₃)₂] (Dipp = 2,6-di-iso-propylphenyl) are reported. In solid state these metal(I) complexes either occur as isolated molecules (Co) or are part of a potassium ion linked 1D-coordination polymer (Cr–Fe). In solution the potassium cation is either ligated within the ligand sphere of the metal silylamide or is separated from the complex depending on the solvent. For iron, we showcase that it is possible to use sodium or lithium metal for the reduction of the metal(II) precursor. However, in these cases the resulting iron(I) complexes can only be isolated upon cation separation using an appropriate crown-ether. Further, the neutral metal(I) complexes are used to introduce NBu₄⁺ as an organic cation in the case of cobalt and iron. The impact of the intramolecular cation complexation was further demonstrated upon reaction with diphenyl acetylene which leads to bond formation processes and redox disproportionation instead of η²-alkyne complex formation.