Cobalt(III) complexes of 1,5,9-triamino-5-methyl-3,7-diazanonane, L1, a new quinquedentate polyamine ligand. Crystal structures of the chlorocobalt(III) and µ-superoxo-dicobalt(III) complexes of L1

Abstract

The polyamine 1,5,9-triamino-5-methyl-3,7-diazanonane (L¹) co-ordinates as a quinquedentate ligand to cobalt(III). The monomers [Co(L¹)X]²⁺(X = Cl^–, NCS^–, or NO₂^–) and the dimers [(CoL¹)₂O₂]ⁿ⁺(n= 4 or 5) were prepared and characterized spectroscopically. The complex [Co(L¹)Cl]Cl[ClO₄] crystallizes in the monoclinic space group P2₁/c, a= 10.471(2), b= 11.878(3), c= 13.284(2)Å, and β= 97.70(1)°. The superoxo complex [(CoL¹)₂O₂][ClO₄]₅·4H₂O crystallizes in the triclinic space group P, a= 8.592(3), b= 9.792(3), c= 12.993(6)Å, α= 95.96(3), β= 97.70(1), and γ= 109.38(3)°. The cobalt–nitrogen bonds are unusually short in both structures, in the range 1.934–1.949(2)Å, and there is considerable strain in the molecules. The cobalt–chlorine bond in [Co(L¹)Cl]Cl[ClO₄] is also short [2.261(1)Å] and the rate of base hydrolysis of this bond is slow. The Raman-active O₂ vibration in the peroxo-bridged dimer occurs ca. 40 cm^–1 to lower wave number than for the deca-ammine analogue, indicative of a slightly longer O–O bond, whereas the O–O bond in the superoxo complex [1.294(14)Å] is shorter than that in the decaammine analogue.