Controlling uranyl oxo group interactions to group 14 elements using polypyrrolic Schiff-base macrocyclic ligands

Abstract

Heterodinuclear uranyl/group 14 complexes of the aryl- and anthracenyl-linked Schiff-base macrocyclic ligands LMe and LA were synthesised by reaction of UO2(H2L) with M{N(SiMe3)2}2 (M = Ge, Sn, Pb). For complexes of the anthracenyl-linked ligand (LA) the group 14 metal sits out of the N4-donor plane by up to 0.7 Å resulting in relatively short M⋯OUO distances which decrease down the group; however, the solid state structures and IR spectroscopic analyses suggest little interaction occurs between the oxo and group 14 metal. In contrast, the smaller aryl-linked ligand (LMe) enforces greater interaction between the metals; only the PbII complex was cleanly accessible although this complex was relatively unstable in the presence of HN(SiMe3)2 and some organic oxidants. In this case, the equatorial coordination of pyridine-N-oxide causes a 0.08 Å elongation of the endo UO bond and a clear interaction of the uranyl ion with the Pb(ii) cation in the second donor compartment.