The Co-ordination number of transition-metal ions. Part VI. Four- and five-co-ordinate complexes of some bivalent metal ions with bis-[2-(2-pyridyl)ethyl]amine

Abstract

Compounds of the types, M dpea X₂ and M dpea XY, are described, where M = Mn^II, Fe^II, Co^II, Cu^II, Zn^II, Cd^II, or Pd^II; dpea = bis-[2-(2-pyridyl)ethyl]amine; X = Cl, Br, or I; Y = ClO₄. It is shown from molecular weight, electrical conductivity, X-ray diffraction, magnetic, and i.r. and electronic spectral measurements that the compounds investigated fall into three structural classes, (i) neutral, mononuclear, five-co-ordinate [Mn dpea Br₂, Co dpea Cl₂, Co dpea Br₂, Co dpea (NCS)₂, Cu dpea Cl₂, Cd dpea Br₂, Cd dpea I₂, Zn dpea (NCS)₂, and possibly Fe dpea Cl₂]; (ii) square planar, cationic (the Pd^II compounds); and (iii) neutral mononuclear, four-co-ordinate (tetrahedral), in which one pyridine of dpea is not co-ordinated [Zn dpea Cl₂, Zn dpea Br₂, and Zn dpea I₂]. The complexes, Mn dpea Cl₂ and Cd dpea Cl₂, may exemplify a fourth structural class in which the metal ions are six-co-ordinate.