Metal complexes of 1,10-Phenanthroline derivatives. VIII. Complexs of 1,10-Phenanthroline-2-carbaldehyde imines

Abstract

Iron(11), cobalt(11) and nickel(11) complexes [ML₂] [BF₄]₂ of a series of related tridentate imine derivatives of 1,l0-phenanthroline-2-carbaldehyde [N-(l,l0-phenanthrolin-2-ylmethylene)alkyl-(or aryl)amines in which the alkyl or aryl group is methyl, ethyl, propyl, isopropyl, butyl, s-butyl, t-butyl, phenyl or benzyl] are described. From the electronic spectra of the nickel complexes an order of field strengths is established which correlates reasonably well with the bulkiness of the imine moiety. All the ligands except that where R = Bu^t effect spin-pairing in iron(11) at room temperature. When R = Bu^t the iron(11) complex is essentially high-spin at room temperature but is predominantly low-spin at 83 K. The magnetism of this substance is typical for that of iron(11) systems in which a gradual spin transition, ⁵T₂ ←→ ^lA_l occurs. In the complexes where R = Bu Bu⁸, Ph, a significant rise in the magnetic moment above room temperature is observed, indicating the presence of some metal atoms in the ⁵T₂ state. Certain of the ligands of high field strength (R = Me, Et, Pr, Pr¹) yield cobalt(11) complexes whose magnetism is indicative of a gradual quartet-doublet transition. The remaining cobalt(11) complexes are high spin.