Five-co-ordinate cobalt(II) and nickel(II) complexes of 1,4,8,11-tetrakis(diphenylphosphinomethyl)-1,4,8,11-tetraazacyclotetradecane (tpta), [MCl(tpta)]X [X = ClO4, BF4, PF6 and B(C6H5)4]. Crystal structures of [CoCl(tpta)]ClO4·C6H6 and [NiCl(tpta)]ClO4·C6H6†

Abstract

A series of five-co-ordinate cobalt(II) and nickel(II) complexes with 1,4,8,11-tetrakis(diphenylphosphinomethyl)-1,4,8,11-tetraazacyclotetradecane (tpta) has been prepared and characterized. The complexes are high-spin paramagnetic substances, 1∶1 electrolytes, consistent with the general formula [MCl(tpta)]X [M = Co or Ni; X = ClO₄, BF₄, PF₆ or B(C₆H₅)₄]. A binuclear cobalt(II) complex of formula [(CoCl₂)₂(tpta)]·H₂O has also been isolated. The crystal and molecular structures of [CoCl(tpta)]ClO₄·C₆H₆ and [NiCl(tpta)]ClO₄·C₆H₆ have been determined. The complexes have a distorted square-pyramidal geometry around the metal which is co-ordinated by four nitrogen atoms from the tpta ligand and an apical chlorine atom bound on the side of the four pendant chains of the macrocyclic ring. The distortions are greater in the cobalt complexes and are of the trigonal-bipyramidal type.