RELATIONSHIP BETWEEN CHELATE RING SIZE AND STEEOCHEMISTRY OF SOME COBALT(III) COMPLEXES CONTAINING QUADRIDENTATE LIGANDS

The three homologous open-chain quadridentate ligands 1,8-diamino-3,6-dithiaoctane (EEE), 1,9-diamino-3,7-dithianonane (ETE), and 1,10-diamino-4,7-dithiadecane (TET) have been used to prepare a number of isomeric dichlorocobalt(III) complexes. It was found that the EEE ligand gave only the blue cis-α-CoEEECl2+ isomer and the ETE ligand gave the green trans-CoETECl2+ and the red-violet cis-β-CoETECl2 + isomers while the TET ligand gave the red-violet cis-β-Co-TETC2+ and the blue cis-α-CoTETCl2+ isomers. In addition, a series of cobalt(III) complexes of the type CoEEEX2n+ (where X- = Br-, Ns-, NCS-, NO2-, oxalate, and 2,2′-bipyridyl) has been prepared and investigated. These latter complexes all appear to have the cis-α configuration. The equilibria trans-CoETECl2+ ⇌ cis-β-CoETECl2+ and cis-β-CoTETCl2+ ⇌ cis-α-CoTETCl2+ have been studied and the relationship between chain length and stereochemistry is discussed in terms of the conformations of the chelate rings. © 1969, American Chemical Society. All rights reserved.