Further iminopyrrolyl complexes of nickel, cobalt, iron and copper: Synthesis and structural characterisation

The reaction between two equivalents of 2-(N-arylformimino)pyrrolyl sodium salts (NaNC4H3C(H) = N-Ar), with Ar = C6H5 (I), 2,6-iPr2-C6H3 (II) or 2-(N-arylformimino)phenanthro[9,10-c]pyrrolyl sodium salts (NaNC16H10C(H)double bond; length as m-dashN-Ar), with Ardouble bond; length as m-dashC6H5 (III), 2,6-iPr2-C6H3 (IV) and one equivalent of nickel(II), cobalt(II), iron(II) and copper(I) halides, in THF, at low temperatures, afforded bis(iminopyrrolyl) or bis(iminophenanthro[9,10-c]pyrrolyl) complexes with different geometries around the metal centres. Nickel(II) derivatives displayed distorted square planar geometries, whereas for cobalt a tetrahedral complex is proposed. The reactions with FeCl2 resulted in very unstable products, giving rise to dimers with pentacoordinated Fe(III) centres. The addition of two equivalents of pyridine to the reaction medium improved the stability of the resulting compound, enabling the formation of a 16-electron Fe(II) complex, which contained simultaneously two iminopyrrolyls and also a pyridine ligand. In the reaction of CuBr with 2-(N-2,6-diisopropylphenylformimino)pyrrolyl sodium salt, a complex with the general formulation [Cu(iminopyrrolyl)]x was obtained. When exposed to the air, this complex gives rise to the corresponding bis(iminopyrrolyl) Cu(II) complex.