Properties and crystal structure of a four-co-ordinate nickel(I) complex with the macrotricycle 1,3,6,8,12,15-hexaazatricyclo[13.3.1.1 8,12]icosane

Abstract

The four-co-ordinate nickel(I) macrocyclic complex R,R,S,S-[NiL]CIO₄(L = 1,3,6,8,12,15-hexaazatricyclo[13.3.1.1^8,12]icosane) has been synthesized by the reduction of the corresponding nickel(II) complex R,R,S,S,-[NiL][CIO₄]₂·0.5H₂O with sodium amalgam in MeCN under nitrogen. It absorbs at 589 (ε= 620) and 355 nm (ε= 3020 dm³ mol^–1 cm^–1). The EPR powder spectrum shows the anisotropic axial g values of g_∥= 2.272 and g_⊥= 2.074. The complex crystallizes in the orthorhombic space group P2₁2₁2₁ with a= 8.681(2), b= 11.358(2), c= 19.146(4)Å and Z= 4. The structure was solved by the heavy-atom method and refined anisotropically to R= 0.0363 and R′= 0.0379 for 1551 observed reflections [I > 3σ(I)] measured with Mo-K_α radiation. It reveals a tetrahedrally distorted square-planar geometry having two sets of Ni–N bond distances, three at 1.978(3)(average) and one at 1.878(4)Å, without any noticeable expansion of the macrocyclic hole.