Preparation and characterisation of organocobalt(III) complexes of tetraaza macrocyclic ligands. Crystal structures of ethyl- and propyl-cobalt(III) complexes of 3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene

Abstract

Several organocobalt(III) complexes of general formula tras-[CoR(L)(OH₂)][ClO₄]₂ have been prepared in moderate yield using a photochemical route (L = a tetraaza macrocycle; R = Me, Et, Pr or Bu). The complexes have been isolated and characterised by microanalyses, ¹H, ¹³C and ⁵⁹Co NMR spectroscopies, and fast atom bombardment (FAB) mass spectrometry. Crystal structures of two of the complexes, trans-[CoR(L)(OH₂)][ClO₄]₂(L = 3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene; R = Et or Pr) establish the trans-geometry, with relatively long Co–O bond lengths of 2.121(3) and 2.29(3)Å respectively, showing the trans influence of the alkyl groups.