Metal complexes of a sexadentate ligand: The occurrence of some solvent clathrates

Abstract

Complexes of iron(II), cobalt(11), nicke1(II), and copper(II) with the sexadentate ligand 1,5-bis-[2-(2-pyridylmethyleneimino)-phenyl]-l,5-dithiapentane (sexa) have been prepared. The iron(II) and cobalt(11) compounds are low-spin while the nickel(II) compounds are high-spin. Evidence is produced to support the contention that the metal atoms are six-coordinate. Many of the complexes were obtained as clathrates containing one or more molecules of water, alcohol, dimethylformamide, or acetone. The infrared spectra indicate that these solvent molecules, which are not readily lost, are not coordinated to the metal ion. A thermogravimetric study of [Fe sexa][FeCl₄]₂,(CH₃)₂CO showed that one molecule of acetone is lost at 260º whereupon the complex begins to decompose. X-ray diffraction data show that this compound has a host framework of four molecules per unit cell; the structure contains cavities into which the acetone molecules fit. These guest molecules determine the type of structure adopted by the clathrate compound.