Playing with different metalloligands [NiL] and Hg to [NiL] ratios to tune the nuclearity of Ni(II)–Hg(II) complexes: Formation of di-, tri-, hexa- and nona-nuclear Ni–Hg clusters

Abstract

Five new hetero-metallic nickel(II)–mercury(II) complexes, [(NiL¹)HgCl₂] (1), [(NiL¹)₂HgCl₂] (3), [(NiL¹) ₂Hg(N₃)₂] (4), [{(NiL²) ₂Hg(N₃)(μ_1,1-N₃)} ₂] (5) and [{(NiL²)₂Hg(N₃)(μ_1,1-N₃)HgCl₂}₂{Hg(N₃)(μ_1,1-N₃)}] (6) have been synthesized by reacting metalloligands [NiL¹] or [NiL²] (where H₂L¹ is N,N′-bis(salicylidene)-1,2-ethylenediamine and H₂L² is N,N′-bis(salicylidene)-1,3-propanediamine) with HgX₂ (X⁻ = Cl⁻ or N₃⁻) at different molar ratios. All five complexes have been characterised by X-ray single-crystal structural, elemental and spectroscopic analyses. In complex 1, the Hg(II) ion is coordinated to two phenoxido oxygen atoms of one [NiL¹] moiety and two terminal chloride ions to form a NiHg dinuclear complex. In the trinuclear complexes 3 and 4, the central Hg(II) ion is coordinated by two terminal [NiL¹] units through two phenoxido oxygens from each and two terminal chloride (in 3) or azide (in 4) ions. The centrosymmetric hexanuclear complex 5 consists of two trinuclear [(NiL²)₂Hg(N₃)(μ_1,1-N₃)] units, where the phenoxido bridges connect two terminal Ni(II) atoms of the trinuclear units. In these trinuclear units, one azido ligand adopts a μ_l,1-briding mode between Hg and Ni whereas the other one is terminal. In the nonanuclear complex 6, two tetranuclear [{(NiL²) ₂Hg(N₃)(μ_1,1-N₃)}HgCl₂] units are linked to a central Hg(II) positioned on a two fold axis, via chlorido, azido and phenoxido bridges. The tetranuclear unit is formed by the addition of a HgCl₂ molecule to a trinuclear [(NiL²)₂ Hg(N₃)(μ_1,1-N₃)] unit, similar to that present in 5. Complex 5 shows weak ferromagnetic interactions (J = +2.1 cm⁻¹) between the two octahedral Ni(II) ions through double phenoxido bridges with a Ni–O–Ni bond angle of 95.87(11)°.