Ligand design and synthesis. II. Linear five-donor-atom compounds derived from 1,5-Dibromo-3-azapentane

Abstract

A series of linear, five-donor-atom compounds, with nitrogen, sulphur, and oxygen donor-atoms, has been prepared to examine the effects of steric crowding on the formation of octahedral complexes. 1,11-Diamino- 3,9-dithia-6-azaundecane (5) and 4-methyl-1,7-di(8?-quinolyl)-1,7- dithia-4-azaheptane (6) form octahedral complexes with Ni(ClO₄)₂ or Co(ClO₄)₂. An increase in the bulkiness of the ligand, as shown by 1,11- bis(dimethylamino)-3,9-dithia-6-azaundecane (7), led to the formation of five-coordinate or partially five-coordinate cobalt(II) and nickel(II) complexes. With 1,11-bis(diethylamino)-3,9-dithia-6- azaundecane (8), a very hindered ligand, no pure cobalt(II) or nickel(II) complexes could be isolated. Several other hindered compounds containing all sulphur, or sulphur and oxygen, central donor- atoms did not form pure complexes when treated with Co(ClO₄)₂ or Ni(ClO₄)₂.