Four-, five-, and six-co-ordinate cobalt(II) and nickel(II) complexes with tetradentate ‘tripod-like’ nitrogen–oxygen and nitrogen–sulphur ligands

Abstract

The tetradentate ‘tripod’ ligands bis-(2-diethylaminoethyl)-2-methylthioethylamine (I), 2-diethylaminoethylbis-(2-methylthioethyl)amine (II), bis-(2-diethylaminoethyl)-2-methoxyethylamine (III), 2-diethylaminoethyl-bis-(2-methoxyethyl)amine (IV), and tris(2-methoxyethyl)amine (V) give with cobalt(II) and nickel(II) salts complexes with general formulae : (A)[MLX]BPh₄(L = ligand, X = Cl, Br, I, or NCS); (B)[MLX]₂[MX₄](X = Br, I, or NCS); (C)[MLX₂](X = Br, I, or NCS). The complexes (A) are high-spin five-co-ordinate with ligands (I)—(IV) and polymeric octahedral with ligand (V). A five-co-ordinate cation and a tetrahedral MX₄^2– anion are present in the complexes (B). The complexes (C) are either five-co-ordinate or octahedral depending on the nature of M and X, and on the steric requirements of the ligand. A general trend towards six-co-ordination is observed in the order (I) < (III) < (II) < (IV) < (V), i.e. with decreasing bulkiness of the ligands. The stronger tendency of cobalt with respect to nickel to give five-co-ordinate complexes is generally confirmed.