Group 12 Metal Complexes of an 18-Membered N2O2S2 Macrocycle Incorporating Two Pyridines: First Examples of an Infinite Mercury(I) Complex and a Dumbbell-Shaped Heteronuclear Complex with a Macrocyclic Ligand

TLDR: NMR titration and comparative NMR data indicate a relatively higher coordination affinity of Cd(II) toward the macrocycle than occurs for Hg(II), in parallel to the situation observed in the solid state.

Abstract: Homo- and heteronuclear group 12 metal (Zn2+, Cd2+, and Hg2+) complexes 1–6 containing a newly designed 18-membered N2O2S2 macrocycle incorporating two pyridine subunits (L) were prepared and structurally characterized. The individual complexes isolated exhibit unusual stoichiometries, geometries, oxidation states, and structural topologies and include an infinite mercurous complex and a heteronuclear dumbbell-shaped complex. Both the Zn(II) complex [Zn(L)][ZnBr4] (1) and the Cd(II) complex [Cd(L)Br2] (2) are mononuclear, with the metal ion located inside the macrocyclic cavity. The six-coordinated Zn(II) center in 1 adopts an octahedral geometry and is shielded from the anion and solvent by the strongly bound macrocycle. The Cd(II) center in 2 is seven-coordinate, being bound equatorially to two N donors, two O donors, and a S donor from the macrocycle and axially to two bromide ions on opposite sides of the macrocyclic plane, adopting a pentagonal-bipyramidal geometry. In the Hg(II) complexations, the c...